The TF930/960 does have a calibration procedure that is performed from
the front panel. Basically, you feed it a stable input from any known
source (so both 1 Hz and 10 MHz from a GPSDO should work) and then
adjust until the displayed frequency agrees with the known input
frequency. The resolution of this setting is quite a bit better than
the stability of the TCXO in the box.
Now, this process could occur either by actually adjusting the frequency
of a VCTCXO in the box using a DAC, or by changing a calibration
constant stored in the memory of the device. I suspect it's actually
the former, because the instructions say that the adjustment path has a
low-pass filter that you need to allow to settle. This wouldn't be
necessary if the calibration simply changed a stored number.
Dave
On 27/02/2015 15:08, Paul Alfille wrote:
I don't think your TTi TF930 has a GPS input to calibrate against, based on
a quick perusal of the data sheet. I would guess that the calibration
constants are thus fixed from the factory (including temperature
coefficients).
On Thu, Feb 26, 2015 at 3:36 PM, James via time-nuts <time-nuts@febo.com>
wrote:
I presume that this is what my TTi TF930 does. Calibration is closed box
so I guess the TCXO is free running and the micro inside just uses
calibration constants.
James
-----Original Message-----
From: Paul Alfille <paul.alfi...@gmail.com>
To: Discussion of precise time and frequency measurement <
time-nuts@febo.com>
Sent: Thu, 26 Feb 2015 19:02
Subject: [time-nuts] Measuring frequency rather than tuning crystal
I have a couple of HP 5370s with the beaglebone brain transplant. They
come
with a nice 10811 that has a little adjustment screw.
Testing against a
Thunderbolt or KS-24361 the 5370 is off by less than 1Hz.
I know the
traditional method would be to adjust the crystal slowly and
make careful
measurements, but since I have a fancy computer in there, I
wonder if I could
just adjust the frequency in software. 64-bit floating
point numbers should
have sufficient accuracy. All reported measurments
would be corrected for the
actual reference frequency.
Basically, I'd have a 10000000.226 Hz internal
reference.
In fact, could I connect the beaglebone to a a GPS 1 pps source
and make
this a GPS-disciplined-software-corrected oscillator.
So my
question is is this a known technique? The discipline feedback
circuit seems a
little different, I'd adjusting for drift and offset, but
not the gain of
control-oscillator
linkage.
_______________________________________________
time-nuts mailing
list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the
instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
