Tektronix S-2 User manual

INSTRUCTION
MIAN UAL Serial Number
Tektronix, Inc.
S.W. Millikan Way @ P. O. Box 500 @ Beaverton, Oregon 97005 @ Phone [phone]
070-0764-00
@ Cables: Tektronix
468

iA rea MM!
@. Th
nstrument | Type ay Sarial’ or
RSL Number with all requests for paris

orse.ky “IME MULTTYIBRATOR—
S ESET
out
Yo tite , Sto
¢ OM TERS
ef
13)
| Pate
/ COMMAND
| oe mMaMokRins
VOLT Mera
i
on
Wie FF ae AOR
eal al
“ UT
a +t)
( aeons
BW) Tes
ft; RPARTS UST FOR
SEMMILGNRUGTOA TYPES Atel me Wosel |

mVOLTS/DIV
TYPE S-2
SAMPLING HEAD
Fig. 1-1. Type 5-2 Sampling Head.

Type S-2
SECTION 1
TYPE S-2 SPECIFICATION
Change information, if any, affecting this section will be found at the
rear of the manual.
General Information
The Type S-2 Sampling Head is a 50Q input, 50 ps rise-
time, plug-in preamplifier for use in some Tektronix 3S-series
sampling units, usch as the Type 352 Sampling Unit. Input
characteristics of the sampling system are controlled by the
type of sampling head in use.
The Type S-2 can be installed directly into the Type 352,
or used remotely on an optional 3 foot or 6 foot extender
cable. Vertical deflection factor of the sampling system is
labeled at the top of the Type S-2 as mVOLTS/DIV; the label
refers to the sampling unit Units/Div switch that is directly
above the head.
A portion of the input signal is provided to the Type 382
Sampling Unit for externally triggering a Type 372 Random
Sampling Sweep. The Type 3S2 allows selection of the trigger
pickoff signal from the Channel A or Channel B sampling
head. The selected trigger pickoff signal is returned to the
Type 352 front panel at the Trig Out connector. The trigger
pickoff signal is useful with any sampling sweep unit for
repetitive signals where the triggering event does not have
to be displayed. (Only the Type 312 random process sampling
allows the triggering event to be displayed when using the
sampling head trigger pickoff signal.
Digital Unit Program Connections
The Type S-2 contains connections at ifs rear that program
both the decimal and the units lamps of a Type 230 Digital
Unit. The S-1 digital control connections pass through the
Units/Div switch of either the Type 355 or Type 386 Program-
mable Sampling Unit, and through the Type 568 Oscilloscope
to the Type 230 Digital Unit.
ELECTRICAL CHARACTERISTICS
The following characteristics apply over an ambient tem-
perature range of 0°C to +50°C. These characteristics
apply only after the Type S-2 has been properly mated to the
sampling unit and indicator oscilloscope, and after suf-
ficient warmup time. For the particular system warmup re-
quirements, refer to the related amplifier and indicator oscillo-
scope instruction manual. (A 5 minute warmup time is required
for Type 382 — 3T2). A procedure for mating the Type S-2 to
the vertical amplifier can be found in the Operating Instruc-
tions section of this manual.
ELECTRICAL CHARACTERISTICS
Characteristics
Performance Requirement
Supplemental Information
Input Resistance 50 within 1%
Measured at DC
Dot Response
Adjustable in the sampling unit to unity
for signals up to 200 mV P-P; when the plus
dot response is adjusted to unity, the minus
dot response will be within 5% of unity
and vice versa.
Operating Input Voltage Range
+1V to —1V with <1 V P-P signals. Step
signals greater than 200 mV require more
than one dot to display 100% of the step
transition.
Maximum Input Voltage
+5 VDC or sine wave of 10 V P-P up to
10 MHz.
Transient Response
Risetime
50 ps or less, 10% to 90%.
Pulse Flatness Deviation
< +5% and —5% in the first 2.5 ns after
the step pulse reaches 50%.
< + and —2% after the first 2.5 ns.
Applies when the step pulse is Tektronix
Type 284 Pulse Output signal through a
20 cm airline.
Displayed Noise 10 mV or less, tangential noise.
Trace Baseline Vertical Shift with
Trigger Repetition Rate Change.
10 mV or less for trigger rate change from
30 Hz to 50 kHz.
1-1

NOTES

Type S-2
SECTION 2
OPERATING INSTRUCTIONS
Change information, if any, affecting this section will be found at the
rear of the manual.
General Information
This section provides the basic information required for
operation of the Type S-2 Sampling Head, including installa-
tion and First Time Operation.
The Type S-2 completes the circuitry of some Tektronix
sampling units, and controls the input characteristics of the
vertical channel by providing the Strobe Generator, Sampling
Bridge, and Preamplifier circuits. Such a sampling unit is
the Type 352, using one or two S-series sampling heads. A
Type 382 and a sampling sweep unit plugged into an indi-
cator oscilloscope completes the sampling system. A choice
of real or equivalent time sampling is provided by the type
of the sweep unit used,
A 502 input resistance allows the use of 509 attenuators
and probes for operation over a wide range of signal volt-
ages.
A portion of the input signal is provided to the sampling
unit. In the Type 382, this signal is selected from Channel A
or B, and returned to the front panel Trig Out connector
for external triggering or sampling sweep units.
Installing the Type S-2 Sampling Head
Fig. 2-1 shows the Type S-2 partially installed into a Type
352 Sampling Unit with Type 561A Oscilloscope and Type
3T2 Random Sampling Sweep. The sampling head {or heads)
can be plugged into the sampling unit as shown, or used
remotely on a special extender cable. Three and six foot
extender cables are available, Order the three foot extender
cable by Tektronix Part No. 012-0124-00, or the six foot
extender cable by Tektronix Part No, 012-0125-00. Contact
your local Tektronix Field Engineer or Representative for
price and availability of these optional accessories.
To insert the Type S-2 into the right or left hand compart-
ments of the sampling unit, proceed as follows:
1. Pull the latch knob (Fig. 2-1} outward from the front
panel {the latch knob will push out normally when the unit
is inserted if the knob is left free to move).
2. Insert the Type S-2 slowly into the compartment, so the
two plastic guides in the compartment engage the S-2,
3. Push the Type S-2 completely into the compartment.
4. Push the latch knob to lock the S-2 in place.
To remove the Type S-2 from the compartment, pull the
latch knob away from the front panel, then pull the unit
from the compartment.
Type $-2
Sampling Head
Latch knob
Fig. 2-1. Installation information.
To use the Type S-2 on an extender cable, install as
follows:
1. Pull the latch knob located on the head end of the
extender cable outward from the panel (the latch knob
will push out normally when the extender is inserted if the
knob is free to move).
2. Insert the extender cable head end slowly into the
desired compartment in the sampling unit so the two plastic
guides in the compartment engage the unit.
3. Push the head completely into the compartment.
4, Push the latch knob to lock the extender cable head
end in place.
5. Connect the Type S-2 to the other end of the extender
cable in a similar manner, and set the latch knob to hold
it in place.
6. To remove the Type S-2 from the extender cable, pull
the latch knob on the front panel of the Type S-2, and remove
the unit from the extender cable,
7. To remove the extender cable head from the sampling
unit compartment, pull the latch knob outward from the
front of the panel, then pull the unit free.
2-1

Operating Instructions—Type S-2
Mating
The vertical deflection factor labeled by the Type S-2, and
the sampling system loop balance (adjusted by the Bridge
Bal control) must be considered when mating a Type S-2
with a sampling unit.
The mVOLTS/DIV label on the Type S-2 names the deflec-
tion factor units of the sampling unit Units/Div switch
located directly above the label. For example, with the Type
S-1 installed in a Type 382 and the Units/Div switch set at
100, each major division of CRT deflection corresponds to
100 millivolts of input signal (when the Variable control is
in the Cal position). The deflection factor is mated to the
indicator oscilloscope CRT by adjusting the sampling unit
Gain control while the Type S-2 is in Channel B. Refer to the
sampling unit manual for its Gain adjustment. Power supplies
and circuit interconnections are made through the two con-
nectors at the rear of the Type S-2.
Bridge Balance
The Bridge Balance control of the Type S-2 should be
adjusted whenever the sampling head is changed from one
sampling unit to another, or is operated on an extender
cable. Location of the control and details of its adjustment
are described in First Time Operation which follows.
FIRST TIME OPERATION
This First Time Operation procedure utilizes, in addition to
the Type S-2, a Type 382, Type 561A, and Type 284. The
Type 3T2 Random Sampling Sweep unit is recommended for
use with the Type S-2 because random sampling permits
viewing the signal in advance of the triggering event. Such
trigger lead-time is required by the Type S-2 with the Type
382 to view fast pulses without a pre-trigger. The Type 284
is used as a signal source.
Setup Information
1. With the Type 561A Power switch off, insert a Tektronix
Type 382 Sampling Unit into the vertical compartment (left)
and a Tektronix Type 3T2 Random Sampling Sweep into the
horizontal plug-in compartment (right).
2. Insert the Type S-2 Sampling Head info Channel A
compartment (left) in the Type 382 leaving the latch knob
free to move. Once the S-1 is seated, push the latch to lock
it in place.
3. Set the Intensity control on the Type 561A fully counter-
clockwise.
4, Connect the Type 561A to a power source which meets
its voltage and frequency requirements.
5. Set the Power switch to on. Allow about 5 minutes
warm-up so the units reach operating temperature before
proceeding.
6. For single-trace operation, set the controls as follows:
2-2
Type 352
Display Mode CH A
Normal-Smooth Normal
A and B Position Midrange
DC Offset Midrange (5 turns
(both Channels} from one end}
Units /Div 100
(both Channels}
Variable (both channels} Cal
Invert (both Channels} Push in
Dot Response Midrange
(both Channels)
B Delay Midrange
Type 312
Horiz Position Midrange
Samples/Div 9 o'clock position
Display Mode Normal
Start Point With Trigger
Sweep Rate 200 ns/Div
Range 10 ps
Display Mag XI
Time Magnifier x5
Variable Cal
Time Position Both fully clockwise
Trig Sensitivity Fully clockwise
Recovery Time Optional
Trigger Polarity +
Trigger Source Ext
Type 284
Square Wave Amplitude 1.0 Vt
Period 1 ps ‘
Mode Square Wave Output
Lead Time Optional
7. Connect the square wave output signal from the Type
284 to the input connector of the Type S-2 through a 50Q
coaxial cable and a X5 attenuator. Connect the trigger
output signal from the Type 284 through a coaxial cable to
the External Input 50Q connector on the Type 372.
8. Advance the Type 561A Intensity control until the free
running trace brilliance is at the desired viewing level.
9. Center the trace on the graticule with the Type 352 A
Position control and/or the DC Offset control. Adjust the
Type 312 Trig Sensitivity control for a stable triggered dis-
play of a two-cycle square wave with an amplitude of
about 2 divisions.
‘Used through <5 attenuator for 0.2 V into the Type §-2.

Adjusting Dot Response
Sequential Sampling
One method of adjusting the Dot Response to unity is to
use a double or multiple-triggered sweep. This causes each
sample to respond te the full signal amplitude and produce
a display similar to Fig. 2-2A or B.
10. To obtain a display similar to that of Fig. 2-2A or B,
turn the Type 312 Trig Sensitivity control clockwise into the
free run region. Then adjust the Recovery Time control until
the desired display appears.
11, Turn the Channel A Dot Response control to obtain
a display showing unity dot response (see Fig. 2-2B). Fig,
2-2A shows greater than unity dot response. This requires
counter-clockwise rotation of the Dot Response control to
obtain unity dot response. The double triggering shown in
Fig. 2-2A and B is useful to adjust the dot response to unity,
but should not be used in making measurements,
12, After the dot response is adjusted to unity, turn the
Trig Sensitivity control counterclockwise into the triggered
region for a stable trace of a properly triggered display
similar to Fig, 2-2C,
Random Sampling
13, Another convenient method of adjusting the dot re
sponse to unity can be shown with random process sampling.
Change the following controls:
Type 3172
Start Point Before Trigger
Time Magnifier < 50
Type 284
Period 100 ns
14. A dot response greater than unity will produce a dis
play similar to Fig. 2-3A. Dot response deviations from unity
are best observed when the Type 372 Time Magnifier is set
at X20 or 50. Adjust the Type 382 Dot Response control
for a unity dot response display similar to Fig. 2-38.
Bridge Balance Adjustment
15. Connect a bench multimeter set for = 30 V full scale
between ground and the Type 382 Channel A Offset jack
Adjust the Type 382 DC Offset contro! until the multimeter
reads 0 Volts. Increase the meter sensitvity and repeat the
adjustment for greater accuracy,
16. Disconnect the coaxial cable from the Type 284, leaving
the other end of the cable connected to the Type S-2 input
connector. Turn the Type 352 Trig Sensitivity control clock-
wise to free run the trace
NOTE
Operating the sampling head without the input
connector terminated by a 501 resistor or coaxial
cable will cause a vertical shift of the zero signal
baseline by a few millivolts. This*is caused by the
Operating Instructions—Type $-2
(Al Double-triggered,
{C) Properly triggered
Fig. 2-2. Typical display for unity dot response adjustment in normal
sequential sampling
2-3

Operating Instructions—Type 5S-2
100 mV/Div
Bridge Bal
Adjustment
Fig, 2-3. Typical display for unity dot response adjustment in random
tampling operation,
strobe kickout signal being reflected from the open
input connector, and arriving back at the sampling
bridge while the bridge is conducting, Because of
this phenomena, set the display zero reference
point with the input circuit terminated, Also use
at least 20 cm airline between the Type S-2 input
and any tunnel-diode pulse generator or circuit
that is sensitive to signals entering its output
circuit.
17. Switch the Type 382 Units/Div control throughout its
range, adjusting the Type S-2 Bridge Bal control for a trace
shift of not over one division as the Units/Div control is
switched from one end to the other, See Fig. 2-4 for the loca-
tion of the Bridge Bal control. This adjustment must be made
whenever the Type S-2 is shifted from one sampling unit to
another, or operated on a sampling head extender cable.
GENERAL OPERATING INFORMATION
Input Signal Connection Precautions
Accurate displays of signals containing very fast transi-
tions or very high frequencies are possible only when the
2-4
Fig, 2-4, Bridge Bal Location.
coupling circuit does not distort the signal. The Type S-2
nput resistance is 502 requiring the use of high quality
509 coaxial cables and attenuators between the signal
source and the sampling head input connector, Tektronix,
Inc, offers several special probes that permit the signal source
oading to be less than that caused by the 502 input resis
tance. See your Tektronix Field Engineer or Representative
about such special coupling devices
Input Voltage Considerations
Proper displays of various signal amplitudes require special
attention to the type of time base generation in use. There
are also input voltage limits that must be observed to prevent
either display distortion or damage to the Type S-2,
For greater details on coupling of high frequency input
signals, and on precautions to be observed, refer to the
A
sampling unit Instruction Manual supplied with your
sampling instruments
Maximum input signal voltage is an important consideraion
in any sampling system. Signals greater than +1 or —1 volt
generally will not permit a valid display. Thus any signals
of greater amplitude should be attenuated in some manner
before being applied to the Type S-2 input connector, Maxi-
mum input voltage without damage to the input termination
resistor is +5 or volts DC, or 10 volts peak to peak
sine wave signals in the frequency domain of 10 MHz or
below
Where unity dot response 1s required, accurate displays
are possible to achieve only when the input amplitude and
the time base generation mode are both considered. The two
time b generation modes are: (1) normal process sampling,
; the CRT, and
; sampling where the dots are not neces-
where each dot is displayed in sequence acro
(2) random process
sarily displayed in a@ sequence that progresses uniformly
across the CRT. [The Type 3T2 Random Sampling Sweep