[time-nuts] Re: What phase variations to expect in a DMTD due to temperature fluctuations?

[Poul-Henning Kamp]

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Erik Kaashoek writes:

> Or should I invest in semirigid coax?

I think you are at the level where you have to treat everything as
suspect, and through well designed experiments try to isolate where
to spend money.

Some randomish input:

1. Take photos of the setup of /all/ your experiments, so you
   later can figure out which ones were affected by the magnetized
   screwdriver or whatever.

2. Make your circuit/experiment constant power.  Having separate
   "idle" and "measure" modes, forces you to wait for thermal
   balance every time you start a measurement.  (One of the few
   things HP only got /almost/ right with the HP3458A)

3. Characterize your sensitivities.  Modulate the power-supply,
   see what happens.  Module the temperature, see what happens.
   kick the table, see what happens.  Turn the experiment 90, 180 and
   270 degrees around as many axis as you can/dare, see what happens.
   Run the experiment in full light and darkness, see what happens.
   If you dont know your sensitivities, you dont know if your
   readings are real or noise, even if they reach statistical
   significance.

4. Pre-owned fridges and freezers make good cheap shielded thermal
   chambers, if you do not plug them in.  If the experiment produces
   too much heat, run constant temperature water through the coils.
   If there is space, add a couple of bricks to add thermal impedance.

And good luck :-)

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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