Tektronix 7d13 User manual

7D13

DIGITAL

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7013

'C2,''''C,'C'd'C(!~;~vj.iol''t

@ 1971 by Tektronix, Inc., Beaverton,

Oregon. Printed

in

the

United States

of

America.

All

rights reserved. Contents

of

this publication may

not

be reproduced

in

any form without permission

of

the

copyright owner.

U.S.A. and foreign Tektronix products covered

by

U.S. and foreign patents

and/or

patents

pending.

®

T

ABLE

OF

CONTENTS

SECTION'

SPECI FICATlON

Introduction

Electrical Characteristics

Environmental Characteristics

Physical Characteristics

SECTION 2 OPERATING INSTRUCTIONS

Installation

MODE/RANGE

Control

and

Front

Panel

Connectors

First Time

Operation

General Operating Instructions

SECTION 3 CIRCUIT DESCRIPTION

Introduction

Block Diagram Description

Detailed Circuit Description

SECTION 4 MAINTENANCE

Preventive Maintenance

Troubleshooting

Replacement Parts

Component

Replacement

Recalibration

After

Repair

SECTION 5 CALIBRATION

Introduction

Test

Equipment

Required

Part

I-Performance

Check

Part

II-Adjustment

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

CHANGE INFORMATION

Page

,.,

'·2

2·'

2-2

2·4

3·'

3-'

3·2

4·'

4·1

4-4

4·5

5·'

5·3

5·7

Abbreviations and symbols used in

this

manual are based

on

or

taken

directly from IEEE

Standard

260

"Standard

Symbols

for

Units",

MI

L·STD·'2B

and

other

standards

of

the

electronics

industry.

Change

information,

if

any,

is

located

at

the

rear

of

this

manual.

7D'3

7013

MOOE/

"ANGE

{:

"'''::P

~g~\

2~n

~v

",0

I

kW

DC

CUI",E..,.

'-J

TII_

"'"

YJfll'N/"C

_ATO+_-C

II~

t.JIoQ

~

.....

"08

•

U'V

__

TO 0Il10

~

DIGITAL

MULnMETlIl

7D13

Fig.

'.'.7013

Digital Multirnet

er.

-

I -

SECTION

1

SPECIFICA

TION

7D13

Change

information,

if

any,

affecting

this section

will

be

found

at

the rear

of

this manual.

Introduction

connectors

regardless

of

the

setting

of

the

MODE/RANGE

control.

The

7013

Digital

Multimeter

plug-in

unit

is

designed for

use with

Tektronix

7000-series Oscilloscopes

equipped

with

a

readout

system.

The

7013

can be used

to

measure DC

voltage,

DC

current,

resistance, and

temperature.

The

output

of

the

7013

is

presented as a digital

readout

on

the

CRT

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

probe

or

a temperature-sensing device

connected

to

the

front-panel

PROBE

connector.

An

analog

temperature

signal

output

is

available

at

the

front-panel

TEMP

OUT

The

electrical

characteristics

listed

in

Table

1-1

are valid

over

the

stated

environmental

range

for

instruments

cali-

brated

at

an

ambient

temperature

of

+20°C

to

+30°C,

and

after

a

20

minute

warmup

unless

otherwise

noted.

Characteristic

DC

VOLTS

Range

Accuracy

+15°C

to

+40°C

O°C

to

+50°C

Polarity

I

nput

Resistance

Maximum Non-Destructive

Input

Voltage

DC

CURRENT

Range

Accuracy

+15°C

to

+40°C

O°C

to

+50°C

Polarity

TABLE

1-1

ELECTRICAL

CHARACTERISTICS

Performance

Requirement

a

to

1000

volts

Within 0.1%

of

reading

±1

count.

Within 0.2%

of

reading

±2

counts.

1000

V peak

between

INPUT con-

nectors.

1500

V

peak

between

either

connector

and

ground.

a

to

2

Amperes

Within 0.5%

of

reading ±2

counts.

Within 0.7%

of

reading

±4

counts.

Supplemental

Information

Four

full-scale ranges

of

±2.000

V,

±20.00

V,

±200.0

V, and

±1000

V.

Automatic

selection and display.

10

M[2

within

1%

on

all ranges.

For

Maximum

Input

Voltage

rating for voltage

measurements

with

voltage/temperature

probe,

see

probe

instruction

manual.

Four

full-scale ranges

of

±2.000

mA,

±20.00

mA,

±200.0

mA, and

±2000

mAo

Automatic

selection and display.

,-,

Specification-7D

13

TABLE

1-1

(cont)

Characteristic

Performance

Requirement

-

.-

DC

CURRENT

(cont)

I

nput

Resistance

Maximum Non-Destructive 3 Amperes

Input

Current

RESISTANCE

Range o

to

2

Mn

Accuracy

+15°C

to

+40°C Within 0.5%

of

reading

±1

count.

O°C

to

+50°C Within 0.8%

of

reading ±2

counts.

Overload

Protection

Reference

Current

Magnitude

(Amperes)

TEMPERATURE

Range

-55°C

to

+150°C

in

one

range.

Accuracy (with

P6058

Probe)

7013

Ambient

Temperature

Range

+15°C

to

+40°C Within 1°C

to

+125°C

O°C

to

+50°C

Within 2°C

to

+125°C

TEMP OUT 10

mV/oC

Accuracy Within 10 mV

Noise Rejection

Normal Mode Rejection Ratio

At

least

30

dB

at

60

Hz increasing

at

20

dB/decade.

Common

Mode Rejection Ratio

At

least

100

dB

at

DC;

80

dB

at

(1

kn

unbalance)

60

Hz.

Recycle Time

Settling

Time

TABLE 1-2

ENVIRONMENTAL

CHARACTERISTIC

Refer

to

the

Specification for

the

associated oscillo-

scope.

1-2

Size

Weight

Supplemental

Information

0.2 V

Full Scale +

0.3

n

Current

Limited by fuse and clamping diodes.

Five full-scale ranges

of

200.0

n,

2000

n,

20.00

kn,

200.0

kn,

and

2000

kn.

Limited by

60

mA fuse.

2V

Full-Scale Resistance (ohms)

Measurements above

+125°C

are subject

to

probe

derating, see

probe

instruction

manual.

Load impedance

must

not

be less

than

2

kn.

200

milliseconds

(5 measurements

per

second)

1.5 seconds

or

less.

TABLE 1-3

PHYSICAL

Fits all 7000-series plug-in

compartments.

1

Pound

12 Ounces

(797

grams)

7D13

SECTION

2

OPERA

TING

INSTRUCTIONS

Change

information,

if

any,

affecting

this section

will

be

found

at

the rear

of

this manual.

General

The

7D13

Digital Multimeter

unit

operates with

the

readout

system

of

a

Tektronix

7000-series oscilloscope

to

provide

the

capability

to

measure

DC

voltage,

DC

current,

resistance, and

temperature.

To

effectively use

the

7D 13,

the

operation

and capabilities

of

the

instrument

should be

known.

This section describes

the

operation

of

the

front-

panel controls, giving first-time and general operating infor-

mation.

Installation

The

7D 13

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.

To

remove, pull

the

release latch

to

disengage

the

7D13

from

the

oscilloscope.

Continue

to

pull

the

release latch

to

re-

move

the

unit

from

the

oscilloscope.

Display

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. Th

is

display

is

written

by

the

CRT beam

on

a time-shared basis with

the

analog waveform

display from

the

other

plug-in units.

The

digital

readout

display

for

the

7D 13 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

7D 13 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.

MODE/RANGE

CONTROL

AND

FRONT

PANEL

CONNECTORS

Introduction

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

®

with

the

function

and use of

the

MODE/RANGE control

and each

connector.

A brief description

of

these and

their

relationship

to

one

another

is

given here. More de-

tailed information relating

to

measurement

applications

is

given

under

General Operating Instructions.

MODE/RANGE

ReSIST~~DC

6....

..

tOOk!!

2V

VOLTS

..

;".

'"

,,;,\

..

.

lOO!!

....

nv}

-.

2t111111

~

.•

2II1II

·····

..

211IlmA

DC

ZA

CURRENT

~

INPUT

1.SkVMAX

TO

GNO

HIGH COM

PAOBE

UiltVMAX

TO

GNO

7013

DIGtTAl

MUlTiMETER

Fig. 2-1.

MODE/RANGE

control

and

Front-Panel

connectors.

MODE/RANGE

Rotary

Switch

Selects

measurement

mode

and

range simultaneously.

Two

sets of

DC

VOLTS ranges select measure-

2-1

Operating

Instructions-7D13

INPUT

TEMP OUT

10mV/oC

RL

;;'2krl

PROBE

General

ment

via either

the

INPUT connec-

tors

or

the

PROBE

connector.

The

selected

input

is

indicated by

front

panel background

tint.

Binding posts labeled HIGH and

COM

provide connection

of

inputs

for resistance, voltage, and cu rrent

measurements. Both INPUT con-

nectors can be floated above chassis

(ground) potential (see Specifica-

tion section).

Pin jack connectors

to

provide an

analog

output

of

temperature

mea-

surement

data

from

temperature

measuring circuit. This

data

is

pro-

vided regardless

of

the

setting

of

the

MODE/RANGE

control.

Four-pin, locking receptacle for

attaching

a voltage/temperature

probe. Pins provide

connection

for

probe

power and signal input.

FIRST TIME OPERATION

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

7D

13

is

placed

in

a

different

oscilloscope.

The

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.

The

tolerances given for

the

digital

readout

are for units

being operated

in

an

ambient

temperature

range

of

+15°C

to

+40

oC.

For

operation outside

of

these limits, refer

to

Table

1-1

in

the

Specification section.

Preliminary

Instructions

1. Install

the

7D 13

in

any available plug-in compart-

ment

of

a 7000-series oscilloscope.

2-2

2.

Connect

the

oscilloscope to a power source which

meets

the

frequency and voltage requirements

of

the

oscil-

loscope power supply.

3.

Turn

the

oscilloscope power on and allow

about

twenty

minutes warmup time.

4.

During

the

warmup period,

set

the

controls as

follows:

Oscilloscope

Intensity

Readout

Counterclockwise

Off

Any controls

not

mentioned can be

set

as desired.

7D13

MODE/RANGE

DC

VOLTS/1 kV

(INPUT connectors)

Digital Display Check

5.

Connect

the

7D13

INPUT connectors together with a

short

piece

of

wire.

6. Advance

the

oscilloscope

Readout

control

to

obtain a

usable digital display on

the

CRT.

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

mAo

9.

The

readout

should read

.000

mA plus or minus

two

counts

(+.002 mA

to

-.002

mAl.

10.

Set

the

MODE/RANGE control

to

RESISTANCE/

200

rI.

11. The

readout

should read within

the

limits

of

00.0

rI

to

00.1 rI (no polarity indicator).

12.

Set

the

MODE/RANGE control

to

RESISTANCE/2

krl.

13.

The

readout

should be within

the

limits

of

000

rI

to

001 rI.

®

14.

Set

the

MODE/RANGE control

to

RESISTANCE/

20

kll.

15.

The

readout

should be within

the

limits of 0.00 kll

to

0.01 kll.

16.

Set

the

MODE/RANGE control

to

RESISTANCE/

200

kll.

17.

The

readout

should be within

the

limits of 00.0

kll

to

00.1

kll.

18.

Set

the

MODE/RANGE control

to

RESISTANCE/2

Mll.

19.

The

readout

should be with

in

the

limits of

000

kll

to

001

kll.

20. Remove

the

piece

of

wire connecting the INPUT

connectors together.

21.

The

readout

display (7D13 only) will be blinking

and will indicate a high value of resistance.

The

unit

is

attempting

to

measure

the

resistance between

the

INPUT

connectors. Since this value exceeds

the

2 Mll range,

the

display blinks

to

indicate over·ranging.

This concludes

the

operational check procedure.

Resistance

22.

Connect

a pair

of

test

leads

to

the

INPUT connec-

tors.

23.

Connect

a 10

kll

resistor between

the

test

leads.

(The value

of

the

resistor

is

not

critical for

the

purposes of

th

is

demonstration.)

24.

The

readout display will read

the

value

of

the

resis-

tor

used.

Set

the

MODE/RANGE switch

to

RESISTANCE/

200

kll

and RESISTANCE/20 kll and notice

that

the

reading changes

to

include more significant figures.

25.

Set

the

MODE/RANGE control

to

RESISTANCE/2

kll and observe

that

the

display blinks

to

indicate over-

ranging.

®

Operating

Instructions-7D13

DC

Current

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

CURRENT/2

mAo

29. With

the

HI

GH

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

__

mAo

Voltage

31.

Remove

the

resistor from

the

Cal

connector

and

disconnect it from

the

HI

test

lead.

32.

Set

the

MODE/RANGE switch

to

DC

VOL

TS/20

V.

33.

Touch

the

HIGH

test

lead

to

the

oscilloscope

Cal

connector.

34.

The

readout

will read

about

+4.00 V (the

exact

reading will depend upon

the

calibration

of

the

oscilloscope

calibrator).

35.

Reverse the test lead connections; i.e.,

connect

the

HIGH

test

lead

to

the

ground

post

and

the

COM

test

lead

to

the

Cal

connector.

36.

The

readout should read the same value of voltage

as

in

step

34

but

with a - polarity indicated.

Temperature

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.

38.

Set

the

MODE/RANGE control

to

TEMPERA-

TURE.

2-3

Operating

Instructions-7D13

39.

The

readout should read

the

room

temperature

within

the

limits listed

in

Table

1-1

of Section

1.

(Alternate

Procedure: Place

the

probe

in

an environment having a

known temperature.)

40. Connect

the

INPUT connectors

to

the

TEMP OUT

pin jack connectors with

the

test

leads.

The

COM

connector

should be connected

to

the

right hand TEMP OUT connec-

tor

(ground).

41.

Set

the

MODE!RANGE control

to

DC

VOLTS/2

V.

42.

The

readout

display will read

out

a voltage corres-

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

reading obtained

in

this step should be 10

mV

X +25 equals

250

mV or +.250

V.

43.

Disconnect

the

test

leads and

the

voltage/

temperature

probe. This completes

the

First Time

Operation Procedure.

GENERAL

OPERATING INSTRUCTIONS

Resistance Measurements

The

7D13 measures resistance

in

five

fu

II-scale ranges

as

follows: 00.0

to

200.0

rl;

000

to

2000

rl;

0.00

k

to

20.00

krl;

00.0

k

to

200.0

krl; and

000

k

to

2000

krl.

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

The

7D13

can measure

DC

voltages up

to

1

kV

in

four

full-scale ranges as follows:

±.OOO

to

±2.000

V;

±O.OO

to

±20.00

V;

±OO.O

to

±200.0

V; and

±OOO

to

± 1000 V.

2-4

The

voltage

to

be measured can be connected

to

the

7D13

via

the

INPUT connectors or a compatible probe con-

nected

to

the PROBE connector. Observe

the

Maximum

Safe

Input

Voltage limits given

in

Table

1-1

in

the Specifi-

cation section for

all

measurements.

To

measure

DC

voltages via

the

INPUT connectors, 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 (if necessary, refer

to

the oscillo-

scope instruction manual).

4. Select

the

desired full-scale voltage range with

the

MODE!RANGE switch. (The ranges

to

be used with

measurements made via

the

INPUT connectors are indi-

cated by

the

orange

tint

of

the

front

paneL)

5. Connect

the

voltage

to

be measured

to

the

INPUT

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

7D 13

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.

5. Connect a compatible probe

to

the

front-panel

PROBE connector.

®

~

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 leads. 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

mAo

To

measure

DC

current

with

the

7D13, 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 (if necessary, refer

to

the oscillo-

scope instruction manual).

4.

Set

the MODE/RANGE switch

to

the desired full-

scale

DC

CURRENT range.

5. Connect the

DC

current

to

be measured

to

the

IN-

PUT connectors.

The

polarity

of

the

current

is

sensed by the

7D13

cir-

cuitry and automatically displayed. The polarity symbol

@

Operating

Instructions-7D13

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

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.

To

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

surface.

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".

Using

a Transistor

as

a Temperature-Sensing Device

Certain

NPN

transistors such as a 2N2484 can be used as

a separate sensor

in

place of the probe tip with little or no

selection

of

the device.

2-5

Operating

Instructions-7013

Typical accuracy,

without

recalibration of

the

7013,

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.

The

temperature-sensing transistor

is

connected

to

the

7013

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.

2-6

Sensing

Transistor

(2N24841

Connector

(rear viewl

Tektronix

Part

Number

131-0778-00

Fig.

2-2_

Schematic

diagram

of

temperature-sensing

transistor

con-

nected

to

probe

connector.

®

7013

SECTION

3

CIRCUIT

DESCRIPTION

Change

information,

if

any,

affecting

this section

will

be

found

at the rear

of

this manual.

Introduction

This section

of

the manual contains a description

of

the

circuitry

used

in the

7013

Digital M

ultimeter

Plug-I

n.

The

description begins

with

a discussion

of

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:

Tektronix

Circuit

Concepts Books (order

from

your

local

Tektronix

Field

Office

or

representative):

Digital Concepts,

Tektronix

Part

No.

062-1030-00.

Power

Supply

Circuits,

Tektronix

Part

No.

062-0888-

01.

Jacob

Millman

and

Herbert

Taub,

"Pulse,

Digital,

and

Switching

Waveforms",

McGraw-Hili,

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

symbology

and

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

All

references to

direction

of

current

in

this

manual

are

in

terms

of

conventional

current;

i.e.,

from

plus

to

minus.

BLOCK

DIAGRAM

DESCRIPTION

The

heavy dashed line on the Block Diagram encloses

the measurement

input

circuits. These circuits

are

isolated

from

the remainder

of

the

7013

circuits

to

allow

them

to

follow

a

common-mode

voltage

up

to

1500 volts.

The

input

®

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 IGml Converter

which

is

within

the

limits

of

the

Floating

Power

Supply.

The

IG

mI Converter converts the positive

or

negative

input

voltage

to

a single-polarity

current

output

for

the

Analog-to-Pulse-Width Converter.

The

IGml Converter also

provides

an

output

indicating

the

relative

polarity

of

the

input

voltage

to

the Polarity

Indicator

circuit.

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

IGml Converter

is

a voltage

proportional

to

the resist-

ance being measured.

The

An

alog-to-Pulse-Width Converter measures the

single-polarity

current

from

the

IG

ml Converter. The

Analog-to-Pulse-Width Converter

is

clocked

by

the Last

Count

pulse

from

the Counter

to

provide

an

output

STORE

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 IGml

Converter.

The

Polarity

I

ndicator

circuit

provides

an

output

to

the

Readout Logic

to

indicate the relative

polarity

of

the

input

voltage.

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

Supply.

The

Counter

circuit

continually

counts

the

40

kilohertz

signal

from

the

Clock.

The

Counter

output

to

the

Memory

circuit

is

in a 1-2-4-8 binary-coded-decimal (BCD)

form.

3-1

Circuit

Description-7D13

Other

Counter'

outputs

are a

two

kilohertz

trigger

to

the

Temperature

Measurement

circuit,

and a Last

Count

pulse

to

the

Analog-to-Pulse-Width

Converter

and

Readout

Logic

circuits.

The

Last

Count

indicates

that

the

Counter

is

full

(has

counted

to

SOOO).

The

Memory

circuit reads

the

1-2-4-S BCD

output

from

the

Counter

on

command

of

the

Analog-to-Pulse-Width

Converter

STORE

COMMAND

output.

Time-slot

data

from

the

Readout

Logic circuit

enables

the

Memory

to

provide a

BCD

output

having

the

proper

time

relationship

to

drive

the

Readout

Logic.

The

Readout

Logic receives

the

BCD

input

from

the

Memory

circuit

and

encodes

data

so

the

oscilloscope read-

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

Input

Switching

General.

The

I

nput

Switching

circuit

consists

of

the

input

sections

of

the

MODE/RANGE

switch,

attenuator

resistors, and

input-protection

components.

(Other

sections

of

the

MODE/RANGE

switch

encode

the

readout

logic

which

is

described

under

Readout

Logic.)

The

I

nput

Switching

circuit

selects and

attenuates,

when

necessary, a

measurement

input

to

provide an

output

volt-

age

to

the

IGml

Converter

circuit.

The

output

voltage, Vx,

appears

across

the

points

labeled Vx and

DVM

Low.

The

output

voltage

should

not

exceed

the

maximum

input

volt-

age limits

of

the

IGml

Converter

(limited

by

the

Floating

Power

Supply

to

plus

or

minus 15 volts).

Thus,

attenuation

of

the

measurement

input

is

necessary

when

it

would

other-

wise exceed

these

limits.

The

Temperature

Measurement

circuit

and

the

Ohms

Converter

have

outputs

which

are

within

the

maximum

input

voltage limits

of

the

IGml

Converter.

Thus,

when

either

of

these

outputs

is

selected

by

the

MODE/RANGE

switch,

it

is

connected

directly

to

the

IGml

Converter

with-

out

attenuation.

3-2

DC

Volts.

When

the

MODE/RANGE

switch

is

set

to

any

of

the

DC

VOLTS

ranges, it

connects

the

INPUT connec-

tors

(or

the

high and low

terminals

of

the

PROBE con-

nector) across

R60.

R60

is

a precision,

tapped,

10 megohm

resistor

which

is

used as an

input

resistor/voltage divider for

the

DC

VOLTS

mode.

Thus,

the

voltage being measured

is

applied across

the

full

10

megohm resistance

of

R60

while

the

Vx

output

is

taken

from

the

appropriate

tap

for each

full-scale

DC

VOLTS range.

DC

Current.

When

the

MODE/RANGE

switch

is

set

to

a

DC

CURRENT

range,

one

or

more

sections

of

R100r

R60

is

connected

as a

shunt

across

the

INPUT

connectors.

The

voltage

drop

resulting

from

a measured

DC

current

through

the

selected

shunt

resistance provides

the

Vx

output

to

the

IGml Converter.

Fuse

F6,

in

series

with

the

shunt

resistance,

protects

R10 and

R60

from

damage

due

to

excessive

input

current.

Rectifier

diodes

CR7-CRS

protect

R10 and

R60

from

damage

due

to

excessive

input

voltage.

Ohms

Converter.

This

circuit

is

made

up

of

constant-

current

source

039

and

U45,

operational

amplifier U32,

high-impedance

input

024,

and

constant-current

source

02S.

A simplified diagram

of

the

Ohms

Converter

circuit

is

shown

in Fig. 3-1.

The

constant-current

source

consisting

of

039

and U45

supplies a

constant

current

through

R36

to

the

output

of

U32

at

pin 6. VR47 sets

the

voltage

at

the

plus

input

of

U45.

The

output

of

U45

at

pin 6

is

fed back

to

the

minus

input

through

the

gate-source

junction

of

039

to

obtain

a

null voltage.

Thus,

the

voltage

at

the

junction

of

the

source

of

039

and

R40

will be

the

same as

the

voltage

set

by

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.

024

effectively inverts

the

inputs

to

U32.

Thus

3-024

becomes

the

plus

input

to

the

operational

amplifier

and pin

7-024

becomes

the

minus

input.

In

the

RESIST-

ANCE ranges, R

60

provides feed back

from

the

output

of

U32

to

the

plus

input

(pin

3-024).

The

operation

of

U32-

024

is

such

that

it

produces

a null voltage

at

the

plus

input

(pin

3-024)

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

RESISTANCE ranges.

Therefore,

the

voltage

drop

required

across

R60

to

produce

a null

is

also fixed.

As

the

MODE/RANGES

switch

is

set

to

the

various

RESISTANCE RANGES,

different

sections

of

R60

are

®

.....

---........;........;.;...;..;====================-===------'---'--'-'-'--'--"----"'======

---

---------------

F12

R12

HIGH

\.

Unknown

c.

Resistance

=;

INPUT

CR14

COM

CR13

200 D

2kD

20 kD

200kD

Lr-------,

2MD

R20

90

K

R38

Constant-

Current

Source

U45,039

Circuit

Description-7D13

9 kD

R60

Vx

to

IGml

Converter

900

D

90 D

10

D

Fig.

3-1.

Simplified

diagram

of

the

Ohms

Converter

circuit.

connected

into

the

circuit.

Since

the

voltage

drop

necessary

across

R60

to

establish a null

at

the

plus

input

(pin

3-024)

is

constant

for

all RESISTANCE ranges,

the

current

through

R

60

must

change as

the

resistance

of

R

60

is

effec-

tively increased

or

decreased_However,

once

the

RESIST-

ANcE

range

is

selected,

the

current

through

the

selected

section(s)

of

R60

is

held

constant

by

U32-024.

This

constant

current

is

available

at

the

HIGH INPUT

connector

through

R12 and F12

to

produce a voltage

drop

across an

unk

nown

resistance

connected

between

the

INPUT connec-

tors.

The

resultant

voltage

drop

across

the

unknown

resist-

ance

produces

an

output

at

the

Vx

connector

which

is

measured

by

the

voltmeter

circuits and read

out

as a resist-

ance

value.

[G

m[

CONVERTER

AND

ANALOG-TO-PULSE-WIDTH

CONVERTER

General

The

[G

m[

Converter

and Analog-to-Pulse-Width Convert-

er circuits measure

input

voltage

Vx

with

respect

to

DVM

Low

from

the

Input

Switching

circuit

and

generate

an

out-

put

signal,

STORE

COMMAND,

to

the

Store

Command

®

Delay stage

of

the

Memory

circuit (diagram 3). Also, an

output

signal, MINUS,

is

provided

to

the

Readout

Logic

to

indicate

that

Vx

is

negative

with

respect

to

DVM

Low;

therefore,

a

minus

(-)

symbol

should be displayed.

The

[G

m[

Converter

and Analog-to-Pulse-Width Con-

verter

circuits, along

with

the

Ohms

Converter,

are powered

from

the

Floating

Power

Supply

to allow

them

to

follow a

common-mode

voltage up

to

1500

volts. Signals

between

the

floating circuits and

other

circuits

in

the

7013

are

transformer-coupled

for

DC

isolation.

[G

m[ Converter

The

[G

m[

Converter

consists

of

0103, 0105, 0108,

0125,0135,0141,

U118,

and

U128.

This

circuit

provides

a single-polarity

current

output

to

be integrated

by

the

Integrator

stage.

The

level

of

this

current

is

determined

by

the

absolute

value

of

Vx

with

respect

to

DVM

Low. Also,

an

output

to

0173

in

the

Polarity

Indicator

circuit indi-

cates

the

polarity

of

Vx

with

respect

to

DVM

Low.

3-3

Circuit

Description-7D13

The

output

signal

is

a

current

into

the

IGml

Converter

from

the

Integrator

current-summing

point

(at

the

gate

of

0152).

U

118

or

U

128

"sink"

the

signal

through

CR

142

as

determined

by

the

polarity

of

Vx.

Field·effect

diode

CR

142 limits

the

maximum

signal

current

amplitude.

0103

provides a

high-impedance

input

to

U

118

for

V

x.

Because

0103

inverts

the

inputs

to

U

118,

pin 3 (gate)

becomes

the

plus

input

to

U

118

and pin 7

becomes

the

minus

input.

Constant-current

sources

0105-0113,

in

con-

junction

with

bootstrap

emitter-follower

0108,

maintain

the

parameters

of

0103

constant

over a

wide

range

of

operating

conditions.

CR101-CR102

limit

the

maximum

value

of

Vx

by

conducting

if

Vx

to

DVM Low

exceeds

about

plus

or

minus

15 volts (referenced

to

floating

ground).

R

115,

Zero

Adjustment,

provides an

adjustment

to

balance

the

quiescent

current

through

the

two

halves

of

0103.

The

voltage level

at

the

output

of

U118

(pin 6) follows

the

voltage level

at

the

plus

input

(pin

3-0103).

The

output

is

fed

back

to

the

minus

input

(pin

7-0103)

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

0125

when

Vx

is

negative

with

respect

to

DVM

Low.

For

zero

or

positive levels

of

Vx,

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

Vx

with

respect

to

DVM

Low,

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

0141

more

negative

than

the

source,

to

pinch

off

cur-

rent

through

0141.

The

signal

current,

therefore,

flows

through

0135

(drain

to

source),

R124, R122,

and

CR119

to

pin 6

of

U118.

The

circuit

operation

for

positive levels

of

Vx

is

similar

to

that

for

negative levels. In

this

case,

0135

is

pinched

off

and

the

signal

current

path

is

through

0141,

R122, R124,

and

CR

130

to

pin 6

of

U

128.

Analog-to-Pulse-Width Converter

Integrator.

The

Integrator

circuit,

made

up

of

0152

and

U

155,

generates

a

ramp

output.

The

ramp

amplitude

and

slope

are

functions

of

the

current

into

or

out

of

the

current-

summing

point

at

the

gate

of

0152.

The

positive-going por-

tion

of

the

ramp

charges

with

the

current

going

to

the

IGml

Converter.

The

ramp

will go positive until reset by

the

reference

current

being

switched

into

the

current-summing

point.

The

voltage level reached by

the

positive

ramp

is

3-4

determined

by

the

amount

of

current

demanded

by

the

IGml

Converter.

The

slope

of

the

negative

portion

of

the

ramp

is

determined

by

the

difference between

the

reference

current

and

the

current

into

the

IGml

Converter.

Fig. 3-2

shows

the

time

relationship

of

the

Counter

out-

put

and

the

Analog-to-Pulse-Width

Converter

circuits.

The

I

ntegrator

ramp

waveform

represents

the

I

ntegrator

output

for

a full-scale

measurement

(e.g.,

2.000

V). Regardless of

the

measurement

input,

the

duration

of

the

ramp

remains

the

same;

the

positive

portion

of

the

ramp

always

ends

at

TO,

corresponding

to

the

Last

Count

from

the

Counter.

Zero-Crossing

Comparator.

The

Zero-Crossing

Compara-

tor,

U

158,

generates

a negative-going pulse

when

the

negative-going

ramp

at

its

input

reaches

the

zero-volt level

(referenced

to

floating

ground).

The

relationship

between

T2

=

FULL

SCALE

OF

COUNTER

RESETS

TO

ZERO

AFTER

T2

COUNTER

OUTPUT

X10

3

INTEGRATOR

RAMP

(OUTPUT)

O-VOL

T

LEVEL

J

INPUTS

0 2

t-

Z

=>

0

U

t-

Vl

<!

-I

3 4 5 6 7 0 2

I

~

:~9DjI

tb

12

1:~,1

U1598

<~.-

_______

_

PIN4

~

lJ

OUTPUTS

C

1598

6

U159D

PIN 11

------==--iU

STORE

COMMAND

Q187

Collector

Fig.

3-2.

Analog-to-Pulse-Width

Converter

circuit

waveforms

showing

their

relationship

to

the

Counter

output.

®

~-~----============-===~=-

===--=~-=-~=-

=-=-;;;;;;-=-=-=-=-;;;;;;-=-==-=-=-=====~

=~-===-

the

ramp and

the

output

of

the

Zero-crossing

Comparator

is

shown

in

Fig_

3-2;

the

input

to

U159B

at

pin 4

is

the

output

of

the

Zero-Crossing

Comparator.

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

are

shown

in Fig. 3-2.

One

input

to

the

flip-flop

at

pin 12-U159D

is

a negative-

going pulse derived

from

the

LAST COUNT

from

the

Counter

through

T168

and

0169.

The

other

input

at

4-U159B

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.

The

output

from pin

6-U

159B (negative-going

pu

Ise)

is

connected

to

the

Reference

Current

Source

to

switch

the

reference

current

into

the

Integrator

current-summing

point.

The

output

from pin

ll-U159D

(positive-going

pu

Ise)

is

connected

to

the

Polarity

I

nd

icator circu it and

to

0187

via

C184

and

T185.

The

resulting signal

at

the

collector

of

0187

is

a negative

pulse,

STORE

COMMAND,

coincident

with

the

Zero-

Crossing

input

to

U159D (see Fig. 3-2). This signal

is

con-

nected

to

the

Store

Command

Delay

circuit

and

to

the

Polarity

Indicator

circuit.

R

efe

rence

Current

Source.

The

Reference Cu rrent

Source,

consisting

of

U145,

0149,

and

0163

supplies a

constant

current

called

the

reference

current,

Ir.

VR144

and

U145

establish a

constant

voltage

at

the

source

of

0149.

R

148,

Gain

Adjustment,

then

provides

adjustment

of

Ir

through

R

148,

R

149,

and

0149.

Ir

is

sinked from

the

drain

of

0149

to

the

Floating

Power

Supply

common

through

CR

165,

VR

164,

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.

Ir

is

now switched

through

CR150

to

the

Integra-

tor

current-summing

point

to

end

the

positive

portion

of

the

ramp

(see Fig. 3-2).

Polarity

Indicator.

The

Polarity Indicator circuit

consisting

of

0173,

U159A,

U159C,

0182,

and

U189A

provides

the

MINUS signal

to

the

Readout

Logic circuit.

MINUS,

when

at

the

LO level, indicates

that

the

polarity

symbol

in

the

readout

display should be a minus

(-)

symbol.

MINUS

is

at

the

LO

level

when

the

relative

polarity

of

Vx

is

negative

with

respect

to

DVM

Low.

®

Circuit

Description-7D13

The

output

of

U118-pin 6 in

the

IGml

Converter

follows

Vx (see IGml Converter). When Vx

is

positive,

the

base

of

0173

is

positive. This results

in

0173

being

saturated.

Thus,

the

collector

of

0173

is

at

its

LO

level

to

inhibit

U159A.

When Vx

is

negative

with

respect

to

DVM

Low,

0173

is

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

ll-U

159D

goes H

I.

The

output

of

U159A

is

connected

to

U189A

through

U159C,

T179,

and

0182

to

set

the

output

of

U189A,

MINUS,

to

a

LO

level.

CLOCK, COUNTER,

AND

MEMORY

Clock

The

Clock consists

of

a collector-coupled astable multi-

vibrator,

0200

and

0206,

and a divide

by

two

counter,

U208B.

The

multivibrator

generates an

80

kilohertz

clock

signal.

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

Delay stage

of

the

Memory

circuit

and

the

Floating Power

Supply.

R203,

Clock, provides

adjustment

of

the

80

kilohertz

frequency.

Counter

The

Counter

circuit consists

of

divide

by

10

counters,

U210, 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 COUNT

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

Indicator.

Memory

The

Memory

circuit

includes

the

Storage Registers,

Store

Command

Delay, and

the

Multiplexers.

Storage Registers.

The

Storage Registers consist

of

U218, U220, U222,

and

U224.

The

Storage

Registers

transfer

the

binary-coded-decimal

Counter

output

to

the

Multiplexers

when

strobed

by

the

STORE

COMMAND

signal

from

the

Store

Command

Delay stage. Thus,

only

the

3-5

Circuit

Description-7D13

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

STORE

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.

The

1000

output

from

9-U224,

is

provided

to

the

Readout

Logic

to

indicate

a

measurement

of

1000

or

more.

1000

is

LO

for

counts

of

1000

or

more.

The

2000

output

from

6-U224

is

provided

to

the

Readout

Logic

to

indi-

cate

a

count

of

2000

or

more.

2000

is

LO

only

for

counts

of

2000

and

greater,

which

enables

the

Over-Range Indi-

cator

circuit.

Store

Command

Delay_

The

Store

Command

Delay

stage consists

of

Q190,

U189B,

U195A,

U195B,

U195C,

U195D,

and

Q216.

The

Store

Command

Delay stage receives

the

STOR

E

COMMAND signal

from

the

Analog-to-Pulse-Width Con-

verter

and

provides

the

STORE

COMMAND

to

the

Storage

Registers.

The

STORE

COMMAND signal

is

slightly

delayed

by

this

stage if

the

STORE

COMMAND

input

occurs

at

the

same

time

that

the

40

kilohertz

Clock

signal

is

triggering

the

Counter.

Otherwise,

an

erratic

or

erroneous

count

would

be

displayed.

Multiplexer.

The

Multiplexer

circuit

consists

of

U260

and

U262.

The

Multiplexers

read

the

1-2-4-8

outputs

from

the

Storage

Registers,

translating

only

four

specific bits

at

anyone

time.

The

time

for

each

character

is

determined

by

the

time-slot

data

from

the

Readout

Logic

circuit

driving

the

Multiplexer

address

inputs.

The

Multiplexer

output

to

the

Digital-to-Analog

Converter

in

the

Readout

Logic

is

a

time-slot

related 1-2-4-8

binary

code.

READOUT

LOGIC

General

The

Readout

Logic

circuit

encodes

the

Indicator

Oscillo-

scope

readout

system

to

display

the

measurement

made

by

the

7D13.

The

Readout

Logic

circuit

also

encodes

the

read-

out

system

to

display

the

appropriate

measurement

units

and

polarity

symbols,

along

with

positioning

the

display

decimal

point

and

ind icating an over-range

measurement.

A discussion

entitled

Introduction

to

the

Readout

System

following

the

7D13

Circuit

Description

gives a brief

description

of

the

readout

system

used

in

Tektronix

7000-series Oscilloscopes.

3-6

Encoding

Format

The

7D13

Readout

Logic

circuit

encodes

the

Rowand

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.

TABLE

3-1

7D13

READOUT

FORMAT

TIME-SLOT

NUMBER

DESCRIPTION

TS-1

Determines

decimal

position.

Also,

encodes

a JUMP

instruction

to

indicate

over-ranging.

TS-2

Not

used

TS-3

Indicates

polarity

of

measurement.

TS-4

Most significant

digit

of

measurement

readout.

TS-5,

TS-6

Remaining

three

digits

of

measurement

TS-7

readout.

TS-8

Encodes

m (milli-) and k (kilo-) prefixes,

V (volts)

and

C (Celsius)

measurement

units.

TS-9

Encodes

A (amperes)

and

.Q

(ohms)

measurement

units.

TS-10

Not

used

Digital-to-Analog

Converter

The

Digital-to-Analog

Converter

circuit

includes D-A

Converter,

U264,

and

time-slot

driver,

Q259.

Time-slot

pulses TS-4, TS-5, TS-6, and TS-7

from

the

I

nterface

Connector

are

connected

to

the

base

of

Q259

via

diodes.

Q259

then

drives

the

ENABLE

input

of

U264

at

8.

The

INPUTs

to

U264

at

pins

2,3,4,

and 5 receive

the

1-2-4-8

binary

code

from

the

Multiplexers.

U264

then

encodes

the

Column

Current

output

at

pin 15 according

to

the

binary

weight

of

each

number;

the

position

of

each

figure

is

determined

by

the

time-slot

pulses (see

Table

3-1).

MODE/RANGE

Switch

The

MODE/RANGE

switch

encodes

the

readout system

by

switching

resistors between

the

appropriate

time-slot

inputs

and

the

Column

and/or

Row

Current

output

lines.

The

readout system then displays the measurement

unit

and

prefix

for

the

measurement

mode

selected, and

the

decimal

point

is

positioned

properly

for

the measurement

range selected.

Also,

a positive

polarity

symbol

(+)

is

encoded

by

the

MODE/RANGE

switch

when set

for

DC

VOLTS,

DC

CURRENT,

and

TEMPERATURE

measurements.

If

the

MINUS

input

to

the

base

of

0278

goes

to

a

La

level,

current

is

added

to

the

Column

Current

output

through

R277 and CR278

during

TS-3.

This

added

current

in TS-3

results in

the

+

symbol

being changed

to

-.

Over-Range

Indicator

The

Over-Range

Indicator,

consIsting

of

0232

and

0228,

causes

the

readout

display

(for

the

7D13

only)

to

blink

when

the

measurement range in

use

is

exceeded.

The

2000

input

to

the

base

of

0228

from

the Storage

Registers

is

HI

when

the

most

significant

digit

is

1

or

O.

This

HI level saturates

0228

to

sink

the

current

through

R234

when

it

is

interrogated

by

time-slot

pulse TS-1.

The

base

of

0228

goes

La

when

the

most

significant

digit

is

2

to

reverse-bias

0228.

Now,

when

R234

is

interrogated

by

TS-1, a

JUMP

instruction

is

added

to

the

Row

Current

output.

The

input

to

0232

base

is

the

LAST

COUNT

pulse

from

the

counter

which

goes

HI

at

the last

count

(approximately

five hertz

repetition

rate). Each

time

the

LAST

COU

NT

goes

HI,

0232

is

saturated

to

sink

the

JUMP

instruction

current

to

ground.

This

causes

the

display

to

blink

at the

repetition

rate

of

the

LAST

COUNT.

Zero-Cancel.

Zero

cancelling

is

encoded

when

the

most

significant

digit

is

0,

so

that

the 0 does

not

appear in

the

readout

display.

This

is

accomplished

during

time-slot

four,

since

this

is

the

position

held

by

the

most

significant

digit.

The

base

of

0238

is

connected

to

9-U224

in

the

Storage Register

circuit.

The

1000

input

to

0238

is

La

when

the

most

significant

digit

is

0,

and HI

for

any

other

value. A HI level

on

the

base

of

0238

saturates

it

to

sink

the

TS-4

current

through

R239

to

ground. A

La

level at

the

base

of

0238

allows

the

TS-4

current

through

R239

to

pass

to

the

Row

Current

output

through

CR239.

This

current

forces a skip in

time-slot

four,

thus cancelling the

initialO.

®

Circuit

Description-7D13

TEMPERATURE

MEASUREMENT

AND

FLOATING

POWER SUPPLY

Temperature Measurement

General.

The

Temperature

Measurement

circuit

consists

of

an

em

itter

coupled mu

Itivibrator

triggered

by

the

two

kilohertz

signal

from

the

Counter

circuit

0301-0305,

cur-

rent level

switch

0315,

demodulator

FETs

0326-0330,

operational

amplifier

U319,

and operational

amplifier

U335.

Theory

of

operation.

Under

the

conditions

of

zero

collector-base voltage and

sufficient

emitter-base voltage,

the

collector

current

of

a transistor

can

be

expressed

as

an

exponential

function

of

the emitter-base voltage and

the

junction

temperature.

By

switching

the

collector

current

between

two

levels,

the

resulting

difference

in emitter-base

voltage

is

a linear

function

of

temperature.

Circuit

operation.

The

temperature-sensing transistor

is

connected in

the

feedback

loop

(via the PROBE connector)

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

collector

current

of

the

temperature-sensing transis-

tor

is

switched between

two

levels

by

0315.

The

current

is

limited

by

R317 when

0315

is

off,

to

about

one-tenth

the

current

through

both

R317 and

R315-0315

when

0315

is

on.

For

a given

current

input,

the

output

of

U319

forward

biases

the

emitter-base

junction

of

the temperature-sensing

transistor

to

the

level necessary

to

maintain

the

input

collector

current. I

nput

current

to

the

operational

amplifier

is

negligible, and

thus

the

input

current

essentially

is

the

collector

current

of

the

temperature-sensing transistor.

The

output

of

U319

at

6

is

a

two

kilohertz

square

wave (and a DC

component)

with

an

amplitude

determined

by

the

temperature

of

the temperature-sensing transistor.

This

signal

is

AC-coupled

through

C329

to

the drains

of

0326

and

0330.

0326

and

0330

demodulate

the

signal

from

the

output

of

U319.

0326-0330

are driven

from

opposite

halves

of

multivibrator

0301-0305,

to

be

turned

on

during

opposite

half

cycles. When

0326

turns

on,

it

restores the negative

extremity

of

the

square wave signal

to

ground. When

0326

is

off

and

0330

on,

the

positive

extremity

is

passed

through

0330

to

C332.

C332

acts

as

a low-pass

filter.

The voltage

developed across

C332

is

the

demodulated

output

of

U319,

and its level

follows

the

average

amplitude

of

the square

waves.

3-7

Tektronix 7D13 User manual

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