[time-nuts] Tbolt temperature sensor

[Tom Van Baak]

Ah, yes, I see that one also shows the same correlation between
oven current (temp) and EFC voltage, but the TI wanders a lot
more. What are the large rapid swings; almost like ringing?

I remember a few years ago there was a long thread about the
effect of changes in oven current on EFC potential due to
common ground lines.

In your plots the EFC correction seems to match so well with
oven current (without clear evidence of the usual thermal lag)
could it be that what you're seeing, and what you're correcting,
is not resonator temperature at all but simply the voltage offset
due to ground currents?

One way to tell for sure is to take your raw syst:stat data and
plot the normalized difference between oven current and -efc.
If you see evidence of time lags then its a good sign that it's
temperature. If the two track well, at short and at long periods,
then I wonder if it's not temperature but current that's being
compensated for.

/tvb

  ----- Original Message ----- 
  From: SAIDJACK at aol.com 
  To: tvb at leapsecond.com 
  Cc: time-nuts at febo.com 
  Sent: Thursday, February 05, 2009 12:59 AM
  Subject: Re: [time-nuts] Tbolt temperature sensor


  Hi Tom,

  yes, they are all GPS locked.

  here is the same OCXO type without proper temp compensation:

  http://www.jackson-labs.com/images/gpsstat.htm

  You can see that now the phase has to change considerably to compensate for the EFC voltage change (because tempco has not been properly established yet).

  To have the TIC compensate, it needs to detect a phase offset first. This error will be prevented if the tempco already compensates properly for temperature changes.

  As the proper tempco is established, the phase offsets diminish in magnitude.

  bye,
  Said

  In a message dated 2/4/2009 21:58:18 Pacific Standard Time, tvb at LeapSecond.com writes:
    In that case, how do you distinguish in the plots between
    the GPS phase locking reaction to the OCXO starting to
    go off-frequency and software temperature compensation?

    How much of the correction in the plots is due to normal
    phase locking against GPS and how much is due to your
    temperature sensing and compensation?