S-4: Difference between revisions

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The S4 sampling plug-in head provides one 50-ohm SMA port with a 25ps risetime. The S4 provides a trigger pickoff signal for internal triggering and is specified for less than 5mV of noise.
{{Plugin Sidebar 2 |
title=Tektronix S-4 |
summary=Sampling Head |
image=Tek-s-4.jpg |
caption=S-4 head |
series={{3S+7S}} |
introduced=1968 |
discontinued=1990 |
manuals=
* [http://w140.com/tek_s4.pdf Tektronix S-4 Manual, copyright 1969 (PDF)]
* [http://w140.com/tek_S4_1985.pdf Tektronix S-4 Manual, revised 1985 (PDF)]
* [http://w140.com/frye_s4_gate.pdf George Frye's Explanation of S-4 sampler in October 1968 Service Scope (PDF)]
}}
The '''Tektronix S-4''' is a sampling head for 7000- and 3S-series samplers.  It was designed by [[George Frye]] and [[introduced in 1968]]. It is the fastest of the S-series plug-in samplers.  


{{BeginSpecs}}
{{Spec | Rise time | 25 ps (observed with [[S-50]] or [[S-52]], 35 ps) }}
{{Spec | Bandwidth | 14.5 GHz }}
{{Spec | Input impedance | 50 Ω (terminated [[SMA connector]])}}
{{Spec | Input range | operating, 1 V<sub>p-p</sub>; max. safe overload, ±5 V }}
{{Spec | Noise | < 5 mV}}
{{Spec | Features |
* trigger signal pick-off for internal triggering
}}
{{EndSpecs}}
==Internals==
The S-4 sampling gate is based upon a traveling wave trapped-charge transmission line in which the sampling window is set by the propagation time of a pulse edge through a thick-film transmission line. This technique requires only a sharp pulse edge rather than a precise pulse width, which is harder to generate.
The sampling diodes are housed in a special coaxial connector that provides a high bandwidth signal path.
The sampling diodes are housed in a special coaxial connector that provides a high bandwidth signal path.
To disassemble the sampler hybrid, first remove it from the sampler board as per the manual.  Remove the input
connector using a 7/32" wrench and remove the 20 dB attenuator with small plyers.  The ceramic board is held
to the housing using roll pins that can be pressed out with a 0.030" pin punch.  The hybrid has six diodes,
each about 0.75mm square.  The cathodes are glued to the gold substrate with conductive epoxy and the anodes
are wire-bonded (twice) over a gap to the next step in the strobe line.  It appears that a standard beam-lead
diode may fit across the gap but cleanly removing a failed diode without damaging the substrate would be
quite difficult.
==Links==
* [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_special/S4.html S-4 page @ amplifier.cd]
* [https://kh6htv.files.wordpress.com/2015/11/an-02a-oscopes.pdf James R. Andrews, ''Comparison of Ultra-Fast Rise Sampling Oscilloscopes''. Picosecond Pulse Labs App Note AN-2a, 1989]
==Pictures==
<gallery>
<gallery>
Image:S4_top.jpg|Top view of the S4 plug-in
File:Tek-s-4.jpg
Image:S4_left.jpg|Left view
File:Tek s4.jpg
Image:S4_right.jpg|Right view
File:S4_top.jpg|Top view of the S4 plug-in
File:S4_left.jpg|Left view
File:S4_right.jpg|Right view
File:S4 schem.png|Schematic
File:Tektronix-S4-sampler-board-strobe.jpg|Sampler board, strobe side
File:Tektronix-S4-sampler-board-preamp.jpg|Sampler board, preamp side
File:Tektronix-S4-sampler-board-hybrid.jpg|Sampler board, disassembled with parts orientation
File:Tektronix-S4-hybrid-internal.jpg|Microphotograph of sampler hybrid
</gallery>
</gallery>
[[Category:7000 and 3S series sampling heads]]

Revision as of 08:14, 23 February 2017

Template:Plugin Sidebar 2 The Tektronix S-4 is a sampling head for 7000- and 3S-series samplers. It was designed by George Frye and introduced in 1968. It is the fastest of the S-series plug-in samplers.

Key Specifications

Rise time 25 ps (observed with S-50 or S-52, 35 ps)
Bandwidth 14.5 GHz
Input impedance 50 Ω (terminated SMA connector)
Input range operating, 1 Vp-p; max. safe overload, ±5 V
Noise < 5 mV
Features
  • trigger signal pick-off for internal triggering

Internals

The S-4 sampling gate is based upon a traveling wave trapped-charge transmission line in which the sampling window is set by the propagation time of a pulse edge through a thick-film transmission line. This technique requires only a sharp pulse edge rather than a precise pulse width, which is harder to generate. The sampling diodes are housed in a special coaxial connector that provides a high bandwidth signal path.

To disassemble the sampler hybrid, first remove it from the sampler board as per the manual. Remove the input connector using a 7/32" wrench and remove the 20 dB attenuator with small plyers. The ceramic board is held to the housing using roll pins that can be pressed out with a 0.030" pin punch. The hybrid has six diodes, each about 0.75mm square. The cathodes are glued to the gold substrate with conductive epoxy and the anodes are wire-bonded (twice) over a gap to the next step in the strobe line. It appears that a standard beam-lead diode may fit across the gap but cleanly removing a failed diode without damaging the substrate would be quite difficult.

Links


Pictures