Re: S-52 drift in TD trigger

Albert Otten

In general you are right Don about allowing for (long) warming up. In this case (7S12, S-52, S-6) the calibration procedures ask for just 5 minutes. But that might be sufficient for the calibration steps even if the drift continues.


--- In TekScopes@..., <tekscopes@...> wrote:

Is all this discussion on drift a fault or just the requirement to allow a reasonable warm up time before making measurements (I guess that's what the discussion is all about). And hence the way the equipment was designed and always operated. Most test equipment instructions  seems to say allow (20 minutes?) warm up before calibrating. Can anyone with past experience and long memories give some insight.

Don Black.

On 11-Sep-13 4:53 AM, aodiversen@... wrote:

I am not conviced that my nice camel is not ok. My other S-52 shows about the same camel, be it with nearly no dip between the humps. What I measure is the TD output, not the snap-off diode (CR66) voltage. It looks like there is a slow oscillation superimposed which causes the humps. I think LR64 might be responsible for this. In the 7S12 the DC bias current for CR66 is supplied via L64 of LR64. When the 7S12 interrupts that current L64 might cause (heavily damped) oscillations.

Meanwhile I followed David's S-53 suggestion. S-53 free running, S-53 Trigger output via delay line and attenuator fed into the S-6. The trigger pulse now drifted to the left, about 500 ps. Similarly I put the S-6 in a 7S11 in the left slot along with the 7S12. Again drift to the left but only 300 ps (here I am not sure the units were completely cooled down initially). I ignore that the 7S11 might introduce drift also; I set the delay dial at minimum.

Inside the 7S12 it means that the delay from S-53 trigger to S-6 strobe pulse increases with temperature. The  path to the internal sampling head contains an extra delay which is set by R380. This extra delay has its own drift of 200 ps it seems.

If the 7S12 determined delay from S-52 (pre)trigger to S-52 TD triggering were constant, then the above findings would imply a drift to the left of the TD pulse. A 600 ps drift to the right can only be explained by an even larger positive drift of 1.1 ns in delay from S-52 (pre)trigger to S-52 TD triggering. I can imagine that this delay, mainly set by R594, is temperature dependent.

Or am I thinking the wrong way around with events coming later and earlier?


--- In TekScopes@..., <tekscopes@...> wrote:

Maybe not only a psych experiment. Now I have a migraine from reading that. But anyway your trigger does look kind of sick. That double hump cannot be the right kind of camel.

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