Tektronix 7D13 User manual

SECTION 1

SPECIFICATION
SECTION 2

OPERATING
INSTRUCTIONS
SECTION 3

CIRCUIT DESCRIPTION
SECTION 4

MAINTENANCE
SECTION 5

CALIBRATION
CHANGE INFORMATION
Page
Introduction

1-1
Electrical Characteristics

1-1
Environmental Characteristics

1-2
Physical Characteristics

1-2
Installation

2-1
MODE/RANGE
Control and Front Panel Connectors

2-1
First Time Operation

2-2
General Operating
Instructions

2-4
Introduction

3-1
Block Diagram Description

3-1
Detailed Circuit Description

3-2
Preventive
Maintenance

4-1
Troubleshooting

4-1
Replacement Parts

q-4
Component Replacement

4-q
Recalibration After
Repair

4-5
I ntrod u ction

5-1
Test Equipment Required

5-1
Part I-~-Performance Check

5-3
Part II--Adjustment

5-7
SECTION 6

ELECTRICAL PARTS LIST
Abbreviations and Symbols
Parts Ordering Information
SECTION
7

DIAGRAMS AND CIRCUIT BOARD ILLUSTRATION
Symbols and Reference Designators
Voltage and Waveform Conditions
SECTION 8

MECHANICAL
PARTS LIST
Mechanical
Parts List Information
Index of
Mechanical Parts Illustrations
Mechanical Parts List
Accessories
Abbreviations and
symbols used in this manual are based on or taken directly from
IEEE
Standard 260 "Standard
Symbols for Units", MIL-STD-12B and other standards of the
electronics industry .
Change information, if any, is located at the rear of this manual .

7D13
INPUT
1 .5kV
MAX t0 GND
HIGH
COM
PROBE
7
.5 tV
MA%
TO GND
J
.-_
_- . .-
n xTeow~x o
DIGITAL
MULTIMETER
7D13
Fig . 1-1 . 7D13
Digital Multimeter .
r
C'

Change information, if
any, affecting this section will be found at the rear
of this manual .
IntroduCtlon

connectors regardless of the setting of
the MODE/RANGE
control .
'The 7D13 Digital Multimeter plug-in unit is designed for
use with - Tektronix 7000-series Oscilloscopes equipped with
a readout system . The 7D13 can be used to measure DC
voltage,
DC current, resistance, and temperature .
TABLE 1-1
ELECTRICAL CHARACTERISTICS
The output
of the 7D13 is presented as a digital readout
on the CR`f of
the associated oscilloscope, along with infor-
mation
encoded by the other plug-in units . This display is
written by the
CRT beam on a time-shared basis with
the
analog waveform
display from the other plug-in units .
Temperature
measurements are made with the P6058

h~he electrical characteristics listed in
Table 1-1 are valid
probe or a
temperature-sensing device connected to the

over the stated environmental range
for instruments cali-
front-panel

PROBE

connector .

An analog temperature

brated at an
ambient temperature of +20 ° C to +30 ° C, and
signal
output is available at the front-panelTEMP
OUT

after a
20 minute warmup unless otherwise noted .
Characteristic

~

Performance Requirement

~

Supplemental Information
DCVO LTS
Range

I

0 to 1000 volts

I

Four full-scale ranges of ±2 .000 V,
±20 .00 V, ±200 .0 V, and ±1000 V .
Accuracy
+15 ° C
to
+40 ° C

I

Within 0 .1% of reading±1 count .
0 ° C to +50 ° C

~

Within 0 .2% of reading ±2 counts .
Polarity

~

~

Automatic selection and display .
Input Resistance

~

~

10 MS2 within 1% on all ranges .
Maximum Non-Destructive

1000
V
peak between INPUT con-

For Maximum Input Voltage
Input Voltage

nectors . 1500 V peak between

rating for voltage measurements
with
either connector andground
.

voltage/temperature probe, see probe
instruction manual .
DC CURRENT
Range

I

0 to 2 Amperes

I

Four full-scale ranges of ±2 .000 mA,
20 .00 mA, ±200 .0 mA, and - 1
-
2000 mA .
Accu
racy
+15
°
C
to +40 ° C

I

Within 0 .5% of reading
±2 counts .
0 ° C to
+50
° C

I

Within 0 .7% of reading ±4 counts .
7D13
Polarity

Auto matic se lection and dis la
__ .-_

.~.-_~ . . ._ ._ . ._ . ______ .___ _ ._ . ._ . .,~~_ .____ m_ . .
.___ ._
. .~~ .~-_
.

_ . .__m_____V___

~ . .d .

. ._ . .__

.~_ .~ ~___ ._

Specification-7D13
Characteristic
DC
CURRENT~(cont)
_ . ._~ .~
Input Resistance
Maximum Non-Destructive
Input C urrent
RESISTANCE
Range
Accuracy
+15 ° C to
+40 ° C
0 ° C to +50 ° C
Overload Protection
Reference Current Magnitude
(Amperes)
TEMPERA - TUBE
Range
Accuracy (with P6058 Probe)
7D13 Ambient ~femperature
Range
+15 ° C to +40 ° C
__ .__ . .__~~Ct°
+5U°
C ... ._ .__ ._ ._
TEMP OU°T 10 mV/ ° C
Settling
Time
Accuracy
Recycle Time
Noise Rejection
Normal Mode Rejection Ratio
Common Mode Rejection Ratio
(1 kS2 unbalance)
TABLE 1-1 (cont)
Performance
Requirement
3
Amperes

~

Limited by fuse and
clamping diodes .
0 to 2
MSZ

I

Five full-scale ranges of
200
.0
S2, 2000 S2,
20 .00 kSt, 200 .0
kSt, and 2000 kSZ .
Within 0 .5% of reading ±1
count .
Within 0 .8% of reading
±2 counts .
-55 ° C to x-150 ° C in one range,
Within 10 mV
At least 30dB at 60Hz
increasing
at 20 dB/decade
.
At
least 100 dB at DC ; 80dB at
60 Hz,
Supplemental I nformation
0 .2 V
Full Scale

+
0 .3 SZ
Current
Limited by60 mA fuse,
2_V

_ _
Full-Scale Resistance
(ohms)
Within 1 ° C to +125 ° C

~

Measurements above +125 ° C are subject
-----_~----~------°-° -------

to probe derating, see probe instruction
Within 2 ° C to ~+125
°
C

manual .
2 kS2 .
--V ~200 milliseconds
(5 measurements p er second)
1 .5 seconds or less .
TABLE 1-2

TABLE 1-3
ENVIRONMENTAL
CHARACTERISTIC

PHYSICAL
Load impedance must not be less than
Refer

to

the

Specification

for

the

associated

oscillo-

Size

Fits all 7000-series plug-in compartments .
scope
.

Weight

1 Pound 12 Ounces (797 grams)

General

with the function and use of the
MODE/RANGE control
The
7D13 Digital Multimeter unit operates with the

and each connector
. A brief
description of these and
readout system of a Tektronix 7000-series oscilloscope to

their relationship to one another is given here .
More de-
provide the capability to measure DC voltage, DC current,

tailed information relating to measurement applications
is given under General Operating Instructions .
resistance, and temperature . To effectively use the 7D13,
the operation and
capabilities of the instrument should be
known . This section describes
the operation of the front-
panel controls, giving first-tirrre and general operating infor-
mation .
Installation
Display
Change
information, if any, affecting this section will be found
at the rear of this manual .
The 7D13 is designed to operate in any plug-in compart-
ment of Tektronix 7000-series oscilloscopes . To install the
7D13 into a plug-in compartment, push it in until it is
seated flush against the front panel of the oscilloscope . T - o
remove, pull the release latch to disengage the 7D 13 from
the oscilloscope . Continue to pull the release latch to re-
move the unit from the oscilloscope .
The output for the 7D13 Digital Multimeter is a digital
readout display presented on the CRT of the oscilloscope in
which the
unit
is operated, along with information encoded
by the
other plug-in units
.
This
display
is
written
by the
CR~1`
beam on a time-shared basis
with the
analog waveform
display from the other plug-in units .
The digital readout display for the 7D13 will appear in
the top division of the CRT in a location corresponding to
the plug-in compartment used . There is no analog output
signal presented on the CRT ; therefore, it is not necessary
to select the 7D13 with the oscilloscope Vertical or Hori-
zontal Mode switches .
The display consists of three full digits plus one for over-
ranging . The measurement units and decimal position in the
display are determined by the MODE/RANGE switch
setting . When the measurement range in use is exceeded,
the display blinks to indicate over-ranging .
I ntroduction
The MODE/RANGE control and all connectors required
for operation of the 7D 13 are located on the front panel of
the unit (see Fig . 2-1 ) . To make full use of the cap-
abilities of this instrument, the operator should be familiar
MODE/RANGE CON°1°ROL AND
FRONT PANEL CONNECI°ORS
MODE/RANGE
Fig . 2-1 . MODE/RANG E control and Front-Panel connectors .
7D13
Rotary Switch

Selects

measurement mode

and
range simultaneously . Two sets of
DC VOLTS ranges select measure-

Operating Instructions-7D13
INPUT

Binding posts labeled HIGH and

3 . Turn the oscilloscope power
on
and allow
about
COM provide connection of inputs

twenty minutes warmup time .
for resistance, voltage, and current
measurements . Both INPUT con-
nectors can be floated above chassis

4 .
During

the

warmup

period,

set the controls

as
(ground) potential (see Specifics-

follows
:
tion section) .
TEMP OUT
10 mV/ ° C
R~~2k52
meet
via either the INPUT connec-

2 .
Connect
the
oscilloscope to a power
source which
tors or the PROBE connector . The

meets the frequency and voltage requirements of the oscil
selected input is indicated by front

loscope power supply .
panel background tint .
Pin jack connectors to provide an
analog output of temperature mea-
surement data from temperature
measuring circuit . l"his data is pro-
vided regardless of the setting of
the MODE/RANGE control .
PROBE

Four-pin,

locking receptacle for

MODE/RANGE

DC VOLTS/1kV
attaching

a

voltage/temperature

(INPUT connectors)
probe . Pins provide connection for
probe power and signal input .
Digital Display Check
General
FIRST °TIME OPERATION

5
.
Connect the 7D13INPUT
connectors
together
with
a
short piece of wire .
When shipped from the factory, the 7D13 has been cali-
brated to meet the specifications listed in Section 1 and is
ready to be used with a readout-equipped Tektronix
7000-series Oscilloscope .
Steps 1 through 21 of the following procedure provide
an operational check to verify satisfactory operation of the
unit and the associated oscilloscope . This portion of the
procedure is intended as a quick functional check only and
should be performed each time the 7D13 is placed in a
different oscilloscope .
~rhe remainder of the procedure demonstrates the basic
operation of the MODE/RANGE control and the front-
panel connectors . It is recommended that the entire pro-
cedure be followed completely for familiarization with the
instrument . Operation of the oscilloscope is described in
the oscilloscope instruction manual .
T'he tolerances given for the digital readout
are for units
being operated
in
an ambient temperature range of
+15 ° C
to +40 ° C . For operation outside of
these limits, refer to
Table 1-1 in the Specification section .
Preliminary Instructions
1 . Install the 7D13 in any available plug-in compart-

13 . The readout
should be within the limits of 000 ~ to
ment of a 7000-series oscilloscope .

001 SZ
.
Oscilloscope
I ntensity

Counterclockwise
Readout

Off
Any
controls not mentioned can be set as desired .
7D13
6 . Advance the oscilloscope Readout control to obtain a
usable digital display on the CRl' . The display should
appear in the upper graticule division .
7 . The readout should read 000 V plus or minus one
count (-001 V to +001 V) .
8 . Set the MODE/RANGE control to DC CURRENT/2
mA .
9 .
The readout should read .000 mA plus or minus two
counts (+ .p02
mA to - .002 mA) .
10 . Set the MODE/RANGE control to RESISTANCE/
200
S2
.
11 . ~"he
readout should read within the limits of 00
.0
~
to 00 .1 52
(no polarity indicator) .
12 . Set
the MODE/RANGE control to RESISTANCE/2
k S2 .

14 . Set the MODE/RANGE control to RESIST - ANCE/

DC Current
20 kS~ .
15 . "T'he readout should be within the limits of 0 .00 kS2
to 0 .01 k5~ .
16 . Set the MODE/RANGE control to RESISTANCE/
200 k S2 .
17 . The readout should be within the limits of 00 .0 kS2
to 00 .1 k S2 .
18 . Set the MODE/RANGE control to RESIS - TANCE/2
M S2 .
19 . The readout should be within the limits of 000 kSl
to 001 k S2
.
20 . Remove the piece of wire connecting the INPUT
connectors together .
21 . °T`he readout display (7D13 only) will be blinking
and will indicate a high value of resistance . The unit is
attempting to meas~~re the
resistance between the INPU'T -
connectors . Since this value exceeds
the 2
MS2
range, the
display blinks to indicate over-ranging .
This concludes the operational
check procedure .
Resistance
22 . Connect
a pair of test leads to the INPU°I` connec-

35 . Reverse the test lead connections ; i
.e .,
connect
the
tors .

HIGH test lead to the ground post and the COM
test lead to
the Cal connector .
23 . Connect a 10 kS2 resistor
between the test leads .
(The value of the
resistor is not critical for the purposes of

36 . Wfhe readout should read the same value of voltage
this
demonstration .)

as in step 34 but with a -- polarity indicated .
24 .
The readout display will read the value of the resis-
tor used . Set the MODE/RANGE switch to RESISTANCE/
200 kS2
and RESISTANCE/20 k52 and notice that the
reading
changes to include more significant figures .
26 . Disconnect the COM test lead from the resistor and
connect it to the oscilloscope ground post .
27 . Set the oscilloscope Calibrator
to
4
V and the Rate
(Calibrator)
switch to DC
.
28 . Set the MODE/RANGE switch to
DC CURREN - I"/2
mA .
29 . With the HIGH test lead still
attached to the resis-
tor, touch the other end of the resistor
to
the
oscilloscope
Cal output connector .
30 . The readout will indicate a current
of approxi-
mately + .4
_ ._ .
mA .
Voltage
31 .
Remove the
resistor
from the Cal connector and
disconnect it from the H I test lead .
32 .
Set the
MODE/RANGE
switch to DC VOLTS/20
V .
33 .
Touch
the HIGH
test lead to
the oscilloscope
Cal
connector
.
34 . The readout will read about -0-4 .00 V (the exact
reading will depend upon the calibration of the oscilloscope
calibrator) .
Temperature
Operating
Instructions-~-7D13
37 . Connect a voltage/temperature probe such as the
P6058 to the 7D13 PROBE connector . Observe the pre-
cautions relating to proper alignment of the connectors as
given in the Probe instruction manual .
25 . Set the MODE/RANGE control to RESISTANCE/2
kS2 and observe that the display blinks to indicate over-

38 . Set the MODE/RANGE control to TEMPERA-
ranging .

TUBE .
2-3

Operating Instructions-7D13
39 . The readout should read the room temperature

The voltage to
be measured can be connected to the
within the limits listed in Table 1-1 of Section 1 . (Alternate

7D13 via the INPU1 -
connectors or a compatible probe con-
Procedure : Place the probe in an environment having a

nected to the PROBE
connector . Observe the Maximum
known temperature .)

Safe Input Voltage
limits given in Table 1-1 in the Specifi-
cation
section for all measurements .
40 . Connect the INPUT connectors to the
TEMP
OUT
pin jack connectors with the test leads . The COM connector

To
measure DC voltages via the INPUT connectors, use
should be connected to the right hand TEMP OUT connec-

the following
procedure :
for (ground) .
41 . Set the MODE/RANGE control to DC VOLT'S/2
V .
2 . Turn the
oscilloscope power on . Allow about twenty
42 . The readout display will read out a voltage corres-

minutes
warmup .
ponding to 10 mV per each degree Centigrade of the tem-
perature reading obtained in step 39 within 0 .1% . For
example, if the reading obtained in step 23 was +25 °
C,
the

3 . Advance the oscilloscope Readout control to obtain a
reading obtained in this step should be 10 mV X +25 equals

usable readout
display (if necessary, refer to the oscillo-
250 mV or
+ .250 V .

scope instruction manual)
.
43 . Disconnect the test leads and the voltage/

4 .
Select
the desired full-scale voltage range with the
temperature probe . This completes the First Time

MODE/RANGE switch . ( - rhe ranges to be used with
Operation Procedure .

measurements made
via the INPUT connectors are indi-
cated by the orange tint of the front panel .)
GENERAL OPERATING INSTRUCTIONS
Resistance Measurements
The 7D13
measures
resistance
in five full-scale ranges as
follows : 00 .0 to 200 .0
S2
; 000 to
2000 S2 ; 0 .00 k to 20 .00
kSt ; 00 .0 k to 200 .0
k5~ ; and 000 k to 2000 kSZ . To operate
the 7D 13 as an
ohmmeter, proceed as follows :
1
.
Install the
7D13 in any available plug-in compart-
ment of a Tektronix
7000-series Oscilloscope .
2 . Turn the oscilloscope power on
. Allow twenty
minutes warmup .
3 . Advance the
oscilloscope Readout control to obtain a
usable readout display (if necessary,
refer to the oscillo-
scope instruction manual) .
4 . Set the
MODE/RANGE control to the desired
RESISTANCE range .
5 . Connect the
INPUT connectors
to
the
resistance to
be measured .
DC Voltage Measurements
1 . Install the 7D13 in any available plug-in compart-
ment of aTektronix
7000-series Oscilloscope .
5 . Connect the
voltage to be measured to the INPU
-
i°
connectors . The readout
will display a "+" preceding the
reading if the HIGH
input terminal is positive with respect
to the COM terminal,
and "~--" if the HIGH terminal is
negative with respect to the COM
terminal .
To
measure DC voltages with the probe, use the
following procedure :
1 . Install the 7D13 in any available plug-in compart-
ment of a Tektronix 7000-series Oscilloscope .
2 . Turn the oscilloscope power on . Allow about twenty
minutes warmup .
3 . Advance the oscilloscope Readout control to
obtain a
usable readout display
(refer to the oscilloscope instruction
manual if necessary) .
4 . Select the desired full-scale
voltage range by setting
the MODE/RANGE control to one of the
four DC VOLTS
ranges with the gray front-panel background .
The 7D13 can measure DC voltages up to 1 kV in four
full-scale ranges as follows : ± .000 to ±2 .000 V ; ±0 .00 to

5 . Connect a compatible probe to the front-panel
±20 .00 V ; ±00 .0 to ±200 .0
V ;
and ±000 to ±1000
V .

PROBE connector .
2-4

CAUTION
When connecting the probe to the PROBE connector,
the two connectors must be correctly aligned .
Damage to the terminals can result from forcing
the
connector and jack together
. Refer
to the probe in-
struction manual .
6 . Apply the voltage to be measured
between the probe
tip and the common strap on
the probe . Do not use the
COM INPUT connector when making a
measurement with
the probe .
7 .
The readout will display a
"+"
preceding the voltage
reading if
the probe tip is positive with respect to the com-
mon strap, and "--" if the probe tip
is negative with respect
to the common strap .
Voltage measurements with the probe are essentially
the
same as with test lead's . The probe is a straight-through
device ; i .e ., it provides no attenuation to extend the
mea-
surement range
.
The
probe is shielded to minimize pickup
of electrostatic
interference . (For more information, see the
instruction manual for the probe .)
DC Current Measurements
The 7D13 will measure DC current in four ranges as
follows : .000 to 2 .000 mA ; 0 .00 to 20
.00 mA ; 00 .0 to
200 .0 mA ; and 000 to 2000 mA .
"To measure DC current with the 7D13, use the following
procedu re :
1 . Install the 7D13 in any available plug-in compart-
ment of a Tektronix 7000-series oscilloscope .
2 . Turn the oscilloscope power on . Allowabout twenty
minutes warmup .
3 . Advance the oscilloscope Readout control to obtain a
usable readout display (if necessary, refer to the
oscillo-
scope instruction manual) .
4 . Set the MODE/RANGE switch to the desired full-
scale DC CURRENT range .
displayed is dependent upon the relative voltage of the two
INPUT connectors . If the HIGH input connector is positive
with respect to the COM input connector, a "+" will be
displayed and vice versa . For current measurements,
a
cur-
rent (electron flow) into the COM connector and out of the
HIGH connector will result in a
"+"
being displayed .
Temperature Measurements
Operating Instructions---7D13
The 7D13, in conjunction with
a temperature sensing
probe such as the P6058, can measure temperatures from
-55 ° C to +150 ° C in one range .
- fo measure temperature, use the following procedure :
1 . Install the 7D13 in
any available
plug-in
compart-
ment of a "Tektronix 7000-series oscilloscope .
2 . Turn the oscilloscope power on . Allow twenty
minutes warmup .
3 .
Advance
the oscilloscope
Readout
control to obtain
a
usable readout display (if necessary, refer to the oscillo-
scope instruction manual) .
4 .
Connect the temperature-sensing probe to the front-
panel PROBE connector .
When connecting
the temperature probe to the
PROBE
connector, the two connectors must be cor-
rectly
aligned . Damage to the terminals can result
from
forcing the connector and jack together . Refer
to
the probe instruction manual .
5 . Set the MODE/RANGE switch to "TEMPERATURE .
6 . Apply the probe sensor tip to the device being mea-
sured . For optimum temperature transfer, the surface of
the device being measured should be coated with silicon
grease and the probe tip should be applied squarely to the
su rface .
7 . Allow
a
sufficient amount of time for the probe tip
to "settle"
before taking a reading . The time required
depends upon several factors . Generally, when the tip is
first applied to the device under test, the readings will
change rapidly
.
As the probe
tip
temperature approaches
the temperature of the device
under test, the reading will
stabilize or "settle" .
5 . Connect the DC current to be measured to the IN-
PUT connectors .

Using a Transistor as a Temperature-Sensing Device
Certain NPN transistors such as a 2N2484 can be used as
The polarity of
the
current is sensed by the 7D13 cir-

a separate sensor in place of the probe tip with little or no
cuitry and automatically displayed . The polarity symbol

selection of the device .
2-5

Operating
Instructions-7D13
Typical accuracy, without recalibration of the 7D 13, can
be expected to be within 1 ° C for
measurements from
--55 ° C to +125 ° C . However, device
parameters could vary,
causing inaccuracies in the temperature readout as great as
±5 ° C .
If the measurement to be made
requires an accuracy
greater than ~5 ° C, the calibration should be checked .
Check the calibration by placing the sensing device in an
environment having a known ambient temperature, and
comparing the readout versus known
temperature . Any
difference
noted at
the test
temperature can be used as a
correction
factor throughout the measurement range of
--55 ° C to +125 ° C .
Connector (rear view)
Tektronix Part Number
131-077-00
The temperature-sensing transistor is connected to the
7D13 through the front-panel PROBE connector using two-
conductor shielded cable and a connector plug (Tektronix
Part Number 131-0778-00) . A wiring diagram Is shown in

Fig . 2-2 . Schematic diagram of temperature-sensing transistor
con-
Fig . 2-2 .

~

netted to probe connector .

Introduction
l"his section of the manual contains a description
of the
circuitry
used in the 7D13 Digital Multimeter
Plug-I n . The
description
begins with a discussion of the the
instrument
using the
Block Diagram given in the Diagrams
section .
Following
the block diagram description is a more
detailed
description,
particularly for circuits unique to
this instru-
ment . If more
information is desired on commonly
used
circuits, refer to the following
textbooks :
Jacob Millman and Herbert
Taub, "Pulse, Digital, and
Switching
Waveforms", McGraw-Hill, New York,
1965 .
Digital
logic techniques are used to perform
many func-
tions within
this instrument . 'The function and operation
of
the logic circuits are
described using logic symbologyand
terminology . For further information,
see Logic Fundamen-
tals in Section 3 of the oscilloscope
instruction manual .
Following the detailed circuit description
is a brief dis-
cussion
of the readout system used in Tektronix
7000-series
Oscilloscopes . If more information is desired on the
readout
system,
refer to the instruction manual for the oscilloscope .
NOTE
Change information, if any,
affecting this section will be
found at the rear of this manual .
7®13
circuit isolation is
accomplished by transformer coupling of
signals and by the Floating
Power Supply .
The Attenuator and
Switching circuit selects and
attenuates, when necessary, inputs to be
measured from the
INPUT connectors, PROBE connector,
Ohms Converter,
and
Temperature Measurement circuits . A positive or nega-
tive output voltage is provided to the
~Gm~
Converter which
is within the limits of the Floating Power Supply .
Tektronix
Circuit Concepts Books (order from your
local Tektronix
Field Office or representative) :

- 1 - he ~Gm~ Converter
converts the positive or negative
input voltage to a single-polarity
current output for the
Digital
Concepts, Tektronix Part No . 062-1030-00
.

Analog-to-Pulse-Width
Converter . The ~G m ~ Converter also
provides an output
indicating the relative polarity of
the
Power Supply Circuits,
Tektronix Part No . 062-0888-

input voltage to the Polarity
Indicator circuit .
01 .
When the MODE/RANGE switch is set to
RESIST-
ANCE, the Ohms Converter measures resistance
connected
between the INPUT connectors . The output
provided to
the ~Gm~ Converter is a voltage proportional to the
resist-
ance being measured .
The Analog-to-Pulse-Width Converter measures the
single-polarity current from the
~Gm~
Converter . The
Analog-to-Pulse-Width Converter is clocked by the Last
Count pulse from the Counter to provide an output S - FORE
COMMAND pulse to the Memory circuit . The time relation-
ship
between
this output pulse and the Last Count is a
direct function of the analog input current from the ~G m ~
Converter .
The Polarity
Indicator circuit provides an output to the
Readout Logic to indicate the relative polarity of the input
voltage
.
AlI references to
direction of current in this manual
are in terms
of conventional current,' i .e ., from plus to
minus .

The Clock generates an 80 kilohertz
clock signal . The
80 kilohertz signal is counted down by the
-2 stage to pro-
vide
a 40 kilohertz signal which is counted by the
Counter
circuit, and which
is used to trigger the Floating
Power
BLOCK DIAGRAM
DESCRIPTION

Supply .
The heavy dashed line on the Block
Diagram encloses
the measurement input circuits . These
circuits are isolated

The Counter
circuit continually counts the 40 kilohertz
from the remainder of the 7D13
circuits to allow them to

signal from
the Clock . The Counter output to the Memory
follow a common-mode voltage up to
1500 volts . - The input

circuit is in
a 1-2-4-8 binary-coded-decimal
(BCD)
form .

Circuit Description--7D13
Other Counter outputs
are a two kilohertz trigger to the

DC Volts . When the MODE/RANGE
switch is set to any
Temperature Measurement
circuit, and a Last Count pulse

of the DC VOLTS
ranges, it connects the INPUT connec-
to the Analog-to-Pulse-Width
Converterand Readout Logic

tors (or the high
and low terminals of the PROBE con-
circuits . -
The
Last
Count indicates that the Counter is full

vector) across
R60 . R60 is a precision, tapped, 10 megohm
(has
counted to 8000) .

resistor which is
used as an input resistor/voltage divider for
the DCVOLTS
mode . Thus, the voltage being measured is
applied across the
full
10
megohm resistance of R60 while
The
Memory circuit reads the 1-2-4-8 BCD output from

the V x output is taken
from the appropriate tap for each
the Counter on comm and of the Analog-to-Pulse-Width

full-scale DC
VOLTS range .
Converter S`I""ORE COMMAND output . - f~ime-slot
data from
the Readout Logic circuit enables the Memory to
provide a
BCD output having the proper time relationship to
drive

DC Current . When
the MODE/RANGE switch is set to a
the Readout Logic .

DC CURRENT
range, one or more sections of R10 or R60
is connected as a
shunt across the INPUT connectors
. The
voltage
drop resulting from a measured DC current
through
T'he Readout
Logic receives the BCD input from the

the selected shunt resistance provides the V x output
to the
Memory circuit
and encodes data so the oscilloscope read-

IGm~
Converter .
out system can display a
digital readout of the measure-
ment .
The Temperature Measurement circuit provides an out-
put voltage
which varies directly with the temperature of a
temperature-sensing transistor (connected to the
Tempera-
ture
Measurement circuit via the front-panel PROBE
connector)
. The output voltage can be selected
by the
MODE/RANGE switch to be measured and
displayed as a
temperature readout . The output voltage is also
available at
the
front-panel TEMP OUT connectors for any
setting of
the
MODE/RANGE switch .
INPUT SWITCHING AND OHMS
CONVERTER

The
constant-current source consisting
of
039
and U45
supplies a
constant current through R36 to the
output of
Input Switching

U32 at pin 6 .
VR47 sets the voltage at the plus input of
General . The Input Switching
circuit consists of the

U45 . The
output of U45 at pin 6 is fed
back to the minus
input sections of the MODE/RANGE
switch, attenuator

input
through the gate-source junction of
039 to obtain a
null voltage
. Thus, the voltage at the
junction of the source
resistors, and input-protection
components . (Other sections

of
039
and R40 will be the same as the voltage
set by
of the MODE/RANGE
switch encode the readout logic
which is described under
Readout Logic .)

VR47 . Since
the voltage across R40, R42,
and R44 is held
constant by
U45-039, the current
through them is adjust-
able by
R44, Ohms Adjustment .
The Input
Switching circuit selects and
attenuates, when
necessary, a
measurement input to provide
an output volt
age
to the
~G,r,~
Converter circuit . The output
voltage, V x ,

024 effectively inverts
the inputs to U32 . Thus pin
appears across the points labeled V x and DVM
Low . The

3-024 becomes the plus
input to the operational amplifier
output
voltage should not exceed the maximum
input volt-

and pin 7-024 becomes
the minus input . In the RESIS
- r ., -
age
limits of the
~Gm~
Converter (limited
by the Floating

ANCE ranges, R60
provides feedback from the output of
Power Supply to plus or minus
15 volts) . Thus, attenuation

U32 to the plus input
(pin 3-024) . The operation of U32-
of the measurement input is
necessary when it would other-

024 is such that it produces
a null voltage at the plus input
wise exceed these limits .

(pin 3-07_4) which is equal to
the voltage established at the
minus input (pin 7-024) . The
constant current through
R36 from U45-039 establishes
a fixed voltage between the
output of U32 and
the minus input (pin 7-024) in
all
The Temperature Measurement circuit and the Ohms

RESISTANCE
ranges . Therefore, the voltage drop required
Converter have outputs which are within the maximum

across R60 to produce
a null is also fixed .
input voltage limits of the ~G m ~ Converter . Thus, when
either of these outputs is selected by the MODE/RANGE
switch, it is connected directly to the
~G,n~
Converter with-

As the
MODE/RANGES switch is set to the various
out attenuation .

RESISTANCE

RANGES, different sections of R60 are
3- 2
Fuse F6, in series with the
shunt resistance, protects
R10 and R60 from damagedue to
excessive input current .
Rectifier diodes CR7-CR8 protect
R10 and R60 from
damage due to excessive input
voltage .
Ohms Converter
. This circuit is madeup of constant-
current source 039
and U45, operational amplifier U32,
high-impedance input 024,
and constant-current source
028 . A simplified diagram
of the Ohms Converter
circuit is
shown in F ig . 3-1 .

Circuit Description-7D13
Fig,
3-1 . Simplified diagram of the Ohms Converter circuit
.
Constant-
Current
Source
U45,
039
DVM Low
connected into the circuit . Since the voltage
drop necessary

Delay stage of the Memory circuit
(diagram 3) . Also, an
across R60 to establish a null at the
plus
input (pin
3-024)

output signal, MINUS, is provided to the
Readout Logic to
is constant for all RESISTANCE ranges, the current

indicate that V X is negative with
respect to DVM Low ;
through R60 must change as the resistance of R60 is effec-

therefore, a minus (--) symbol should be displayed .
tively increased or decreased . However, once the
RESIST-
ANCE range is selected, the current through the selected
sections) of R60 is held constant by U32-024 . This

The ~G m ~ Converter and Analog-to-Pulse-Width Con-
constant current is available at the HIGH INPUT` connector

verter
circuits, along with the Ohms Converter, are powered
through R12
and F12 to produce a voltage drop across an

from the Floating Power
Supply to allow them to follow a
unknown
resistance connected between the INPU1~ connec-

common-mode voltage
up to 1500 volts . Signals between
tors . The resultant voltage drop across the unknown resist-

the floating circuits and
other circuits in the 7D13 are
ance produces
an output at the V x connector which is

transformer-coupled
for DC isolation .
measured by the
voltmeter circuits and read out as a resist-
ance value .
~G,nI
CONVERTER AND
ANALOG-TO-PULSE-WIDTH
CONVERTER
The ~G, i -i~ Converter consists
of 0103,0105,0108,
General

0125, 0135, 0141,0118, and
U 128 . - T - his circuit provides
a single-polarity current output
to be integrated by the
The ~G m ~ Converter and
Analog-to-Pulse-Width Convert-

Integrator stage . The level of this
current is determined by
er circuits measure input voltage V X
with respect to DVM

the absolute value of V x
with
respect to
DVM Low . Also,
Low from t he Inp ut Switching circuit
and generate an out-

an output to 0173 in the
Polarity Indicator circuit indi-
put signal, STORE COMMAND, to the
Store Command

Gates the polarity of V X with
respect to DVM Low .
IG,~-,~
Converter
3-3

Circuit Description-7D13
The
output signal is a current into the
~G,-n~
Converter

determined by the amount of current demanded by the
from
the
Integrator
current-summing point (at the gate of

~Gm~
Converter . l~he slope of the negative portion of the
Q152) .
U 118 or U 128 "sink" the signal through CR 142 as

ramp is determined by the difference between the reference
determined

by the

polarity of V x .

Field-effect diode

current and the current into the
~Gm~
Converter .
CR 142 limits the maximum signal current amplitude .
Fig . 3-2 shows the time relationship of the Counter out-
Q103 provides a high-impedance input to U118 for V x ,

put and the Analog-to-Pulse-Width
Converter circuits . The
Because Q103 inverts the inputs to U118, pin 3 (gate)

Integrator ramp waveform
represents the Integrator output
becomes the plus input to U118 and pin 7 becomes the

for a full-scale measurement (e .g ., 2
.000
V) . Regardless
of
minus input . Constant-current
sources Q105-Q113, in con-

the measurement input, the duration of the ramp remains
junction with bootstrap emitter-follower Q108, maintain

the same ; the positive portion of the ramp always ends
at
the parameters of Q103 constant over a wide range of

T0, corresponding to the Last Count from the Counter .
operating
conditions . CR101-CR102 limit the maximum
value of V x by conducting if V x
to
DVM
Low exceeds
about plus or minus

15 volts (referenced
to floating

Zero-Crossing Comparator . The Zero-Crossing Compara-
ground) . R115, Zero Adjustment, provides an adjustment

tor,
U158, generates a negative-going pulse when the
to balance the quiescent current through the two halves of

negative-going ramp
at
its input reaches
the zero-volt level
Q103 .

(referenced to floating ground) . The relationship between
The voltage level at the output of U118 (pin 6) follows
the voltage level at the plus input (pin 3-Q103) . The output
is fed back to the minus input (pin 7-Q103) to obtain a
null ; the feedback path is determined by the polarity of V x .
The voltage level at the output of U128 (pin 6) follows
the level at the gate of Q125when V x is negative with
respect to DVM Low . For zero or positive levels of V x ,
however, the output of U 118 is negative .
The operational

amplifier

(U 118

or

U 128) with the
negative voltage level output becomes the output signal
current sink . Assuming a negative value of V x with respect
to DVM Low, pin 6-U118 will be negative to forward bias
CR 119 . CR 119 becomes the feedback path between the
output and the minus input of U118 . VR139 keeps the gate
of Q141 more negative than the source, to pinch off cur-
rent through Q141 . The signal current, therefore, flows
through Q135 (drain to source), R 124, R 122, and CR 119
topin6ofU118
.
~T - he circuit operation for positive levels of V x is similar
to that for negative levels . In this case, Q135 is pinched off
and the signal current path is through Q141, R122,R124,
and
CR 130 to
pin
6 of U 128 .
Analog-to-Pulse-Width
Converter
3-4
T2 = FULL SCALE
OF
COUNTER
RESETS
TO
HERO
AFTER - r2
COUNTER
OUTPUT X10 3
INTEGRATOR
RAMP
(OUTPUT)
0-VOLT LEVEL -
INPUTS
OU`rPUTS
z
O
U
F
N
Q
J
0 1 2 3 4 5 6 7 0 1 2
L_L_L_-_l__ .L . ._l_ ._l-_1- .- 1 ._--1__ ._ .L__
TZ TO T1
Integrator . The Integrator circuit, madeup of Q152 and
U155, generates a ramp output . ~l - he ramp amplitude and
slope are functions of the current into or out of the current-
summing point at the gate of Q152 . The positive-going por-
tion of the ramp charges with the current going to the
~G m
~
Converter . The ramp will go positive until reset by the
reference current being
switched into the current-summing

F ;y .3-2 .Analog-to-Pulse-Width Converter circuitwaveformsshowing
point . The voltage

level

reached

by
the positive ramp is

their relationship
to the Counter output .
STORE
COMMAND
0187 Collector

the ramp and the output of the Zero-crossing Comparator
is

The
output of U 118-pin 6 in the ~G,- r ,~ Converter
follows
shown in Fig . 3-2 ; the input to U159B at pin 4 is the

V x (see
~Gm~
Converter) .
When V x is positive, the
base of
output of the Zero-Crossing Comparator .

0173 is positive .
This results in 0173 being saturated
.
Thus, the collector
of 0173 is at its LO level to inhibit
U 159A .
Zero-Crossing Flip-Flop
. The Zero-Crossing Flip-Flop is
an
RS flip-flop made up of U159B and D . This circuit has
two inputs and two complementary outputs, all of which

When V x is negative
with respect to DVM Low, 0173
is
are shown in Fig . 3-2 .

reverse biased by the
LO
level
at its base . The resulting HI
level at the collector of 0173 enables
U159A . U159A will
have an output each time
the input from pin 11-U159D
One input
to
the flip-flop
at pin 12-U159D is a negative-

goes HI . l~he output of
U159A is connected to U189A
going pulse derived
from the LAST - COUNT from the

through U159C, T179, and
0182 to set the output of
Counter
through T168 and 0169 . The other input at pin

U189A, MINUS, to a LO level .
4-U 159B is the
negative-going pulse from the Zero-Crossing
Comparator . The output
pulses
from
the flip-flop are
initiated by the Last Count input and terminated
by the
Zero-Crossing input .

CLOCK, COUNTER, AND
MEMORY
Reference
Current Source . The Reference Current
Source, consisting of U145, 0149, and 0163 supplies a
constant
current called the reference current, I r . VR144
and U145 establish
a constant voltage at the source of
0149 . R148, Gain Adjustment,
then provides adjustment
of I r through R 148, R 149, and
0149 .
I r is sinked from the drain of 0149 to the
Floating
Power
Supply common through CR165, VR164,
and 0163
when pin 6-U159B is HI . When the Last Count
pulse sets
pin
6-U159B to LO, 0163 is turned off to
reverse bias
CR165 . I r is now switched through CR150
to the Integra-
tor
current-summing point to end the positive
portion of
the ramp
(see Fig . 3-2) .
Clock
The Clock consists of
a collector-coupled astable multi-
The output from pin 6-U159B (negative-going pulse) is

vibrator, 0200 and
0206,
and
a divide by two counter,
connected to the Reference Current Source to switch the

U208B .
reference current into the Integrator current-summing
point . The output from pin 11-U159D (positive-going
pulse) is connected to the Polarity Indicator circuit and to

The multivibrator generates an 80 kilohertz clock signal .
0187 via C184 and T185 .

The 80 kilohertz signal is divided by two by
U208B to
provide a 40 kilohertz clock signal . The 40 kilohertz signal
is connected
to the Counter circuit, the Store Command
The resulting
signal at the collector of 0187 is a negative

Delay stage of the Memory circuit
and the Floating Power
pulse,
STORE COMMAND, coincident with the Zero-

Supply . R203, Clock, provides adjustment of the 80
Crossing input to U159D (see Fig . 3-2) . - f~his signal is con-

kilohertz frequency .
nected to the Store Command Delay circuit and to the
Polarity Indicator circuit .
Counter
The Counter
circuit consists of divide by 10 counters,
0210,
U212,
and
U214, and a divide by eight counter,
U208A .
The Counter counts the 40 kilohertz clock signal
to provide
binary-coded-decimal outputs to the Memory .
The 2 kilohertz pulse from U212
is connected to the
Temperature Measurement circuit for switching
. Also, the
positive LAST COUN7 output from
U208A is connected to
the Analog-to-Pulse-Width Converter to indicate
a full
count ; and to the Readout Logic to clock
the Over-Range
I nd icator .
Memory
Circuit Description--~7D13
The Memory circuit includes the Storage Registers, Store
Command
Delay, and the Multiplexers .
Polarity Indicator
. The Polarity Indicator circuit
consisting of 0173,
U 159A, U 159C, 0182, and U 189A
provides the MINUS
signal to the Readout Logic circuit .

Storage Registers . - rhe Storage Registers consist of
MINUS, when at
the LO level, indicates that the polarity

U218, U220, U222,
and U224 . The Storage Registers
symbol in the readout
display should be a minus (--)

transfer
the binary-coded-decimal Counter output to the
symbol . MINUS is at the
LO level when the relative polarity

Multiplexers when
strobed by the STORE COMMAND
of V x is negative
with respect to DVM Low .

signal from
the Store Command Delay stage . Thus, only the

Circuit
Description--F7D13
Counter output up to the time of the STORE COMMAND
signal is transferred to the Multiplexers and Readout Logic,
while the count made after the S~("ORE COMMAND is not
passed
on .
The Storage Register outputs to the Multiplexers are
inverted in order to drive the Digital-to-Analog Converter in
the Readout Logic, a negative-input device .
would be displayed .

TS-8
Multiplexer . The Multiplexer circuit consists of U260
and U262 . The Multiplexers read the 1-2-4-8 outputs from

TS-9
the Storage Registers, translating only four specific bits at
any one time . The time
for
each character is determined by

----------
the time-slot data from the Readout Logic circuit driving

TS-10
the Multiplexer address inputs . ~I"he Multiplexer output to

-°°-~~
the Digital-to-Analog Converter in the Readout
Logic is a
time-slot related 1-2-4-8 binary code .
General
3-6
READOUT LOGIC
Encoding Format
l°he Store Command Delay stage receives the STORE

---

_ ._
._-
._
COMMAND signal from the Analog-to-Pulse-Width Con-

TS-4
verter and provides the STORE COMMAND to the Storage
Registers . 1 - he Sl`ORE COM MAN D signal is slightly delayed

~°'°~w_ .___w__
by this stage if the Sl ° ORE~COMMAND input occurs at the

TS-5, TS-6
same time that the 40 kilohertz Clock signal is triggering

TS-7
the Counter . Otherwise, an erratic or erroneous count

-------__
._ .-
The
7D13
Readout Logic circuit encodes the Row and
Column output lines (pins B37 and A37 respectively of the
Interface Connector) according to the format given in Table
3-1 . The time-slot pulses from the oscilloscope readout
system are provided to the Readout Logic circuit through
the Interface Connector . Several of the time-slot pulses are
also connected to the Memory circuit to address the Multi-
plexers .
l°he 1000 output
from pin 9-U224,
is
provided
to
the
Readout
Logic to indicate a measurement of
1000 or
more .

TABLE 3-1
1000 is
LO
for counts of 1000 or more . - 1`he 2000 output

7D13 READOUT FORMAT
from pin 6-U224 is provided to the Readout Logic to indi-

_ .~_ ._ .___ .____ ._ .

__

.-___ .__ ._ ._ ._____~ . . .__
Gate a count of 2000 or more . 2000 is LO only for counts

TIME-SLOT ~`
of 2000 and greater, which enables the Over-Range Indi-

NUMBER

DESC RIPTI ON
cator circuit .

~~_ . ,_ .____~__ .

_ :_ ~--~, .__ .~______ _ ." . ._ . . .a .__ .

. . . . .. ...

. .
TS-1

_
y Determines decimal
position . Also,
encodes a JUMP instruction to
indicate
Store Command Delay . 'The Store Command Delay

over-ranging .
stage
consists of 0190, U 189B, U 195A, U 195B, U 195C,

-------
U195D,
and
Q216 .

TS-2

~ Not used
TS-3
measurement units .
Not used
Digital-to-Analog Converter
Indicates polarity of
measurement .
Most significant digit of measurement
readout .
Remaining three digits of measurement
Encodes m (milli-) and k (kilo-) prefixes,
V (volts) and C (Celsius) measurement
units .
Encodes A (amperes) and SZ (ohms)
The Digital-to-Analog Converter circuit includes D-A
Converter, U264, and time-slot driver, 0259 .
The Readout Logic circuit encodes the Indicator Oscillo-
scope readout system to display the measurement made by

'I - ime-slot pulses
TS-4, TS-5, 1°S-6, and TS-7 from the
the 7D13 . The Readout Logic circuit also encodes the read-

Interface
Connector are connected to the base of 0259 via
out system to display the appropriate measurement units

diodes . 0259 then drives the ENABLE input of U264 at
and
polarity
symbols,
along with
positioning
the
display

pin
8 .
decimal point and indicating an over-range measurement .
The INPU~Ts to 0264 at pins 2,
3,
4,
and 5 receive the
A discussion entitled Introduction to the Readout

1-2-4-8 binary code from the
Multiplexers . U264 then
System following the 7D13 Circuit Description gives a brief

encodes the Column Current output
at pin 15 according to
description of the readout system used in Tektronix

the binary weight of each number ; the
position of each
7000-series Oscilloscopes .

figure is determined by the time-slot pulses
(see 1~'able 3-1 ) .

Over-Range Indicator
The
Over-Range Indicator, consisting of 0232
and

Circuit operation . The temperature-sensing
transistor is
0228, causes the
readout display (for the 7D13 only) to

connected in the feedback loop (via the
PROBE connector)
blink when the
measurement range in use is exceeded,

of operational amplifier U319 with the
collector at the
minus input, and the emitter connected
to the output
through R320 . The base is grounded .
The 2000 input to
the base of 0228 from the Storage
Registers is HI when the
most significant digit is 1 or 0 .
This HI level saturates 0228
to sink the current through
R234 when it is interrogated by time-slot
pulse TS-1 . T - he
base of 0228 goes LO when the most significant
digit is 2
to reverse-bias 0228 . Now, whenR234 is
interrogated by
1 - S-1, a JUMP instruction is added to
the Row Current
output .
For a given current input, the output of U319 forward
biases the
emitter-base junction of the temperature-sensing
'The
input
to 0232 base is
the
LAST COUN~f pulse
from

transistor
to the

level

necessary to

maintain the
input
the counter which goes HI at the last count (approximately

collector
current . Input current to the operational
amplifier
five hertz repetition rate) . Each time the LAST COUNT

is negligible,
and thus the input current essentially is the
goes HI,
0232 is saturated to sink the JUMP instruction

collector current
of the temperature-sensing transistor .
current
to ground . This causes the display to blink at the
repetition rate of the
LAST COUNT .
The output of
U319 at pin 6 is a two kilohertz square
wave (and a DC component)
with an amplitude determined
Zero-Cancel . Zero cancelling is encoded when the
most

by the temperature of
the temperature-sensing transistor .
significant digit is 0, so that the
0does not appear in the

This signal is
AC-coupled through C329 to the drains of
readout display . This is accomplished during time-slot four,

0326 and
0330 .
since this is the position held by the most significant digit .
0326 and 0330 demodulate the
signal from the output
°C`he base of 02 .38 is conne cted to pin 9-U224 in the

of 0319 . 0326-0330 are driven
from opposite halves of
Storage
Register circuit . The 1000 input to 0238 is
LO

multivibrator 0301-0305, to be
turned on during opposite
when the most significant
digit is 0, and HI for any other

half
cycles . When0326 turns on, it
restores the negative
value . A HI level on the
base of 0238 saturates it to sink

extremity of the square wave signal to ground
. When0326
the T - S-4 current through
R239 to ground . A LO level at

is off and
0330 on, the positive extremity is
passed through
the base of 0238 allows the
TS-4 current through R239 to

0330 to
C332
.
C332 acts as a low-pass filter . - The voltage
pass to the Row
Current output through CR239 . This

developed across
C332 is the demodulated output of U319,
current forces a skip in time-slot
four, thus cancelling the

and its level follows
the average amplitude of the square
initial 0 .

waves .
MODE/RANGE
Switch

TEMPERATURE
MEASUREMENT AND
°Che
MODE/RANGE switch encodes the readout system

FLOATING
POWER SUPPLY
by switching resistors
between the appropriate
time-slot

Temperature
Measurement
inputs and the Column and/or
Row Current output lines
.
The readout system then
displays the measurement unit

General . The Temperature
Measurement circuit consists
and prefix for the measurement
mode selected, and the

of an emitter coupled
multivibrator triggered by the two
decimal point is positioned properly
for the measurement

kilohertz signal
from the Counter circuit 0301-0305,
cur-
rangeselected .

rent level switch 0315,
demodulator FE - fs 0326-0330,
operational amplifier
U319, and operational amplifier
U 335 .
Also, a positive polarity symbol (+)
is encoded by the
MODE/RANGE switch when set for
DC VOLTS,DC
CURREN
. . f . ',
and TEMPERATURE
measurements . If the

Theory of operation . Under the
conditions of zero
MINUS
input to the base of 0278 goes
to a LO level,

collector-base voltage and sufficient emitter-base
voltage,
current
is added to the Column Current
output through

the
collector current of a transistor can be
expressed as an
R277 and
CR278 during 1 - S-3 . - This added
current in TS-3

exponential function of the emitter-base voltage
and the
results in the
.
symbol being changed to - .

junction
temperature . By switching the collector
current
between two levels,
the resulting difference in emitter-base
voltage is a linear
function of temperature .
Circuit
Description---7D13
The collector current of the temperature-sensing
transis-
tor is switched between two levels by
0315
.
The current is
limited by R317 when0315 is off, to about
one-tenth the
current through both R317 and R315-0315 when0315
is
on
.
3-7

Circuit Description-7D13
The voltage developed across C332 is connected to the

age for
each supply is determined by a temperature-
plus input of the output operational amplifier, U335 . The

compensating zener
reference diode which sets the base
output of U335 at pin 6 is fed back to the minus input

voltage of the series regulator
transistor .
through
R337 and R339 .
R337,
(temperature) Gain, pro-
vides adjustment of the feedback to the minus input so that

INTR®pUC"I - ION "C'O ~"HE READOUT` SYSTEM
the output of U335 can be calibrated to be 10 millivolts per
degree Celsius . R346, Offset, adjusts the bias on U335 for

IntroduCtlon
an output of 0 volts when the temperature of the
temperature-sensing transistor is zero degrees Celsius .

The following discussion is provided to acquaint the
7D13 user with the Readout System used in Tektronix
7000-series Oscilloscopes . Since the oscilloscope Readout
The voltage output of U335 is connected directly to the

System provides the digital readout for the 7D13, it is
front-panel TEMP
OUT
connectors
to
provide
an analog

necessary to relate the function of the 7D13 to the Read-
temperature signal . This voltage output is also connected to

out System to gain a better understanding of the 7D13
the input of the ~Gm~ Converter when the MODE/RANGE

operation . A detailed circuit description of the 7000-series
switch is set to TEMPERATURE . This voltage is measured

Readout System is given in the oscilloscope instruction
by the voltmeter circuits and read out as a temperature

manual .
measurement .
FIOating Power Supply

The Readout System in
the 7000-series oscilloscopes
provides alpha-numeric display
of information encoded by
The

Floating Power Supply is a DC-to-DC Converter

the plug-in units . This display is presented on the CRT, and
supplying outputs of +15 volts, ---15 volts, and +5 volts

is written by the CRT beam on a time-shared basis with the
from the-~-15-volt supply in the Indicator Oscilloscope .

analog waveform display .
The Floating Power Supply consists of inverter
0408-0415 . Emitter-follower 0401 drives 0408 through
R404 from the 40 kilohertz Clock pulse .
The center-tapped primary winding of transformer T420
is the collector load for 0408 and 0415 . Since only 0408
or 0415 is conducting at any one time, the inverter is
chopping at a 20 kilohertz rate, or one-half the input fre-
quency .
Data is encoded on these output lines either by con-
necting resistors between them and the time-slot input lines
The secondary windings
of 1"420 provide a square-wave

or by generating equivalent
currents . The resultant output
output to bridge rectifiers CR422 and CR440 . Each bridge

is a sequence
of analog current levels on the row and
consists of four separate diodes .

Each

output of the

column
output lines . The row and column current levels are
Floating
Power
Supply
is regulated by a series regulator

decoded by the Readout System to address a character
transistor ;
0433, 0438,
and 0447 for the +15-volt,

matrix
during each time-slot, thus selecting a character to
--15-volt,
and +5-volt
outputs respectively . The output volt-

be displayed or a special instruction to be followed .
The Readout System
The
Readout System produces a pulse train consisting of
10 negative-going pulses called time-slots . 1- hese pulses are
assigned time-slot numbers corresponding to their relative
position in the pulse train . Each time-slot pulse is directed
to one of ten output lines, labeled TS-1 through TS-10
(time-slots one through ten) and are connected to the verti-
cal and horizontal plug-in compartments . Two output lines,
row and column, are connected from each channel (two
channels per plug-in compartment) back to the Readout
System .

Change information,
if
any, affecting
this section will be found at the rear of this manual .
I ntroduction

Lu brication
This section
of the manual contains maintenance infor-

Use a cleaning-type lubricant
on shaft bushings, inter-
mation for
use in preventive maintenance, corrective

connecting plug contacts, and
switch contacts . Lubricate
maintenance, and troubleshooting of the 7D13 .

switch detents with a heavier grease
. A lubrication kit
containing the necessary
lubricating materials and instruc-
tions is available through any Tektronix
Field Office . Order
Further maintenance information relating
to
component

Tektronix Part Number 003-0342-00
.
color codes and soldering techniques can be found in the
instruction manuals for the 7000-series oscilloscopes .
General
Preventive maintenance, consisting of cleaning, visual
inspection, lubrication, etc ., performed on a regular
basis,
will improve the reliability of this instrument . Periodic
checks on the semiconductor devices used in the unit are
not recommended as a preventive maintenance measure .
See semiconductor-checking information given under
Troubleshooting .
The following is
provided to augment information
Cleaning

contained in other sections
of this manual when trouble-
shooting the 7D13 . .1"he
schematic diagrams, Circuit
Description, and Calibration sections
should be used to full
advantage . "fhe Circuit Description
section gives detailed
information on circuit behavior
and output requirements .
Avoid the use of chemical
cleaning agents which
might damage the plastics in this
instrument . Avoid

Troubleshooting Aids
chemicals containing benzene, toluene,
xylene,
acetone, or similar solvents .

Diagrams . Circuit diagrams are given on foldout pages in
Section 7 . The circuit number and
electrical value of each
component in this instrument
are shownon the diagrams .
Front
Panel . Loose dust may be removed with a
soft

Important voltages are also shown .
cloth or a dry paint
brush . Water and mild detergent may
be used ;
however, abrasive cleaners should not be used .
Circuit Board . ~fhe circuit board used in the 7D13 is
outlined on the schematic diagrams, and a photograph of
Interior . Cleaning the interior
of the unit should pre-

the
board is shownon the back of the Block Diagram . Each
cede calibration, since the cleaning
process could alter the

board-mounted electrical component is identified on the
settings of the calibration adjustments
. Use low-velocity

photograph by its
circuit number .
compressed air to blow off the
accumulated dust . Hardened
dirt can be removed with a
soft,
dry
paint brush, cotton-
tipped swab, or cloth dampened with
a mild detergent and

Component and Wiring Color
Code . Colored stripes or
water solution .

dots on resistors and capacitors signify electrical values,
PREVENTIVE MAINTENANCE
Recalibration
General
`TROUBLESHOOTING
7D13
`To ensure accurate measurements,
the 7D13 should be
checked after each 1000 hours of
operation or every six
months if used infrequently . A
complete performance
check procedure is given in Part I of Section
5 .
The performance check procedure can be helpful in
isolating major troubles in the unit . Moreover, minor
troubles not apparent during
regular operation may be
revealed and corrected .

Maintenance--~7D73
tolerances,
etc ., according to the EIA standard color code .

3 . Visual Check . Visually check the portion of the
Components
not color coded usually have the value printed

instrument in which the trouble is suspected . Many troubles
on the body .

can be located by visual indications, such as unsoldered
connections, broken wires, damaged circuit boards,
damaged components, etc .
The insulated wires used for interconnection in the
7D13 are color coded to facilitate tracing a wire from one
point to another in the unit .

4 . Check Instrument Performance . Check the calibra-
tion of the unit, or the affected circuit by performing
Part I
- Performance Check Procedure of Section 5 . The apparent
Semiconductor Lead Configuration . Fig . 4-1
shows the

trouble may only be a result of misadjustment and
may be
lead configuration of the semiconductor
devices used in this

corrected by calibration . Complete calibration instructions
instrument .

are given in Part I I of Section 5 .
~`roubleshooting Equipment
5 . Check Voltages and Waveforms . Often the defective
The following equipment is useful for troubleshooting

component
or stage can be located by checking for the
the 7D13 :

correct
voltage or waveform in the circuit . Typical voltages
and Waveforms
are given on the diagrams ; however, these
1 . Semiconductor Tester--Some means of testing the

are
not absolute and may vary slightly between instru-
transistors, diodes, and FET's used in this instrument is

means .
To obtain operating conditions similar to those used
helpful . A transistor-curve tracer such as the Tektronix

to take these
readings, see the instructions in the Diagrams
Type576 will give the most complete information .

section .
2 . DC Voltmeter and Ohmmeter-A
voltmeter for

6 . Check Individual Components . The following
checking voltages within the circuit and an
ohmmeter for

methods are provided for checking the individual compo
checking resistors and diodes are required .

nents in the 7D13 . Components which are soldered in place
are best
checked by disconnecting one end to isolate the
measurementfrom the effects of surrounding circuitry .
3 . Test Oscilloscope-A test oscilloscope
is required to
view Waveforms at different points in the
circuit .
A . TRANSISTORS AND
INTEGRATED CIRCUITS .
The best check of transistor
and integrated circuit opera
A Tektronix 7000-series Oscilloscope with
7D13 Digital

tion is actual performance under
operating conditions . If a
Multimeter unit, 7B-series Time-Base
unit, and a 7A-series

transistor or integrated circuit
is suspected of being defec-
Amplifier unit with a 10X probe will
meet the needs for

tive, it can best be checked by
substituting a component
items 2 and 3 .

known to be good ; however, be sure that
circuit conditions
are not such that a replacement might
also be damaged . If
substituting transistors are not available, use a
dynamic
TroubleshOOtlng
Procedure

tester (such as Tektronix Type
576) . Static-type testers
- This troubleshooting procedure is arranged
in an order

maY
be used, but since they
do
not
check operation under
which checks the simple trouble possibilities
before pro-

simulated operating conditions,
some defects may go
ceeding with extensive troubleshooting,

unnoticed . Fig . 4-1 shows base pin and socket
arrangements
of semiconductor devices . Be sure the power
is
off
before
attempting to remove or replace any transistor
or integrated
1 . Check Control Setting . An incorrect setting of the

circuit .
MODE/RANGE switch can indicate a trouble that
does not
exist . If
there is any question about the correct function or
operation
of the MODE/RANGE control or of any front
panel connector, see the Operating Instructions section .

Integrated circuits can
be checked with a voltmeter, test
oscilloscope,
or by direct substitution . A good under-
standing of the
circuit description is essential to trouble-
2 . Check Associated
Equipment . Before proceeding

shooting circuits
using integrated circuits . Use care when
with troubleshooting of
the 7D13, check that the equip-

checking voltages and
Waveforms around the integrated
ment used with
this instrument is operating correctly . If

circuits so that adjacent
leads are not shorted together . An
possible, substitute
a multimeter unit known to be

integrated-circuit
test clip provides a convenient means of
operating
correctly into the indicator unit and see if the

clipping a test
probe to the 14- and 16-pin integrated
problem persists
. Check that the input is properly con-

circuits . This device
also doubles as an integrated-circuit
nected and that the
interconnecting leads are not defective .

extraction tool .
4- 2