7S12

The Tektronix 7S12 is a Time Domain Reflectometer / Sampler plug-in for 7000-series scopes. It occupies two mainframe plug-in bays (one vertical, one horizontal).

The 7S12 has two bays for S-series plug-in modules ("heads"). The right bay accepts a pulse generator or a trigger recognizer plug-in, whereas the left bay accepts a sampling plug-in.

The typical configuration is to have an S-6 on the left and an S-52 on the right for time domain reflectometry, or a sampling head like the S-4 on the left and an S-53 on the right as a generic sampler.

The 7S12 can also control an optional 7S11 through its left side contacts, adding a second input channel.

Y axis can be scaled in voltage (mV) or distance (ρ) units, X axis in time or distance.

Key Specifications

Sweep modes	Single / Repetitive / Manual / External input
With S-6 and S-52	Pulse: 200 mV into 50 Ω Rise time: < 35 ps for incident step, < 45 ps for displayed reflection Jitter: < 10 ps
Sweep modes	free-running single manual external input
Weight	2.13 kg (4.7 lbs)

Links

• Tektronix 062-1244-00: Time-Domain Reflectometry Measurement Concepts, James A. Strickland, 1969. pages. PDF, OCR, 6.2 MB
• Service Scope No. 45, August 1967 - Time-Domain Reflectometry Theory
• Tek 7S12 @ amplifier.cd
• Tek 7S12 @ barrytech.com
• Evaluation of 7S12 performance (video)
• 7S12 extender board by Dave Partridge

Pictures

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  Front view without sampling head plug-ins

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  Front view with S-6 sampling head and S-52 pulse generator

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  7S12 TDR "self portrait" in 7613 storage mainframe

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  7S12 as a sampler, displaying a 1 GHz sine using a S-6 sampling head and S-53 trigger recognizer, 2^nd channel (top) on a 7S11 with S-4 sampling head.

Inside

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  Left side

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  Left side with cover. Side contacts to interface 7S11 are exposed.

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  Right side

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  Top view

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  Horizontal board

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  Vertical board

Measurements

TDR

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  TDR "Self Portrait" — pulse reflected on S-6 "through" path (approx. 120 ps one way)

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  7S12 displaying the incident pulse from an S-52 (nom. < 25 ps) through an S-6 head (nom. < 30 ps). Displayed rise time ~35 ps confirms spec.

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  7S12/S-6/S-52 displaying pulse reflection from ~ 5 in semi-rigid SMA cable. Stored display of two traces. Left trace: cable only, right trace: cable plus SMA-to-BNC adapter (~ 25 mm)

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  7S12/S-6/S-52 displaying reflected pulse from end of 5 in semi-rigid SMA cable. Stored display overlaying multiple traces, left to right: cable alone, SMA-to-BNC adapter added, BNC f-f adapter added, (cheap) 50 Ω terminator added.

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  Full pulse pattern of a 7S12/S-52 in real time (top trace) and sampled (bottom trace) shown simultaneously on 7844. 7S12 trace at slowest possible sweep.

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  S-52 pulse in real time (top trace) and sampled (bottom trace) shown simultaneously on 7844. Approximately equal time scales.

Probe rise times

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  Rise time of a P6202 500 MHz FET probe measured on a 7S12 with S-52 and S-4 (in a 7844 mainframe), at 1 ns/Div

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  Rise time of a P6202 500 MHz FET probe measured on a 7S12 with S-52 and S-4 (in a 7844 mainframe), at 100 ps/Div

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  P6230 Rise time, no ground lead

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  P6230 Rise time, no ground lead, enlarged – 9.2 * 20 ps = 184 ps (equiv. to 1.9 GHz bandwidth)

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  P6230 with "low inductance" ground lead – rise time 400 ps, bandwidth 875 MHz

As a generic sampler

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  7S11 with S-4 and 7S12 with S-6 and S-53 displaying a 1 GHz sine in normal mode without storage. Sampling is evident.

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  7S11 with S-4 and 7S12 with S-6 and S-53 displaying a 1 GHz sine in high-res mode with variable-persistence storage on a 7613.