[time-nuts] Is anyone using Keithly 776 Freq counter TICfunction?

[Bob Camp]

Hi

If the OCXO is off by 1x10^8, the pps will be moving 10ns per second. You
will get roughly 10 seconds of data before you wrap around the 10 MHz. If
the OCXO is indeed this far off, you probably want something lower than 10
MHz on the "stop" channel. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Magnus Danielson
Sent: Tuesday, August 16, 2011 1:24 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Is anyone using Keithly 776 Freq counter
TICfunction?

On 15/08/11 05:36, Paul Cianciolo wrote:
> Hello
>
> I have a properly working Keithly 776 Frequency counter that has the TIC
using the A and B inputs.
> I have z3801 that is considered my house reference, that 10 MHz output
goes to the A input.
>
> A double oven RAKON oscillator is connected to the is connected to the B
input
> Both signals are square waves.
>
> Using a frequency comparator the Rakon oscillator is adjusted to 1 part in
10-8
> I was assuming that I would see on the FReq Counter a display in degrees a
number between 0 360  that was constantly cycling
> The whole reason for this post and my previous one is to get sample out of
the counter in terms of a voltage, log these voltages,  manipulate them and
then try to graph the results to try and duplicate Allan Variance and
Deviations even if only in a very crude manner for now.
>
> There is an analog output  in the back of the counter.
> Does this seem feasable?  Or maybe there is another counter that would
work better
>
> Thank you again for any help

A recommended setup is to:

1) Trigger measurement by the PPS
2) Use the reference 10 MHz as start of TIC
3) Use the DUT 10 MHz as stop of TIC
4) Log measured time interval start->stop using preferably digital output

Pick up TimeLab to do the post-processing.

If you can't trigger the measurement as described, then using the PPS as 
start signal can be used. You depend much more on the particular GPSDO 
then (a topic in itself).

If you can't do digital readout over RS232 or GPIB then using that 
analog tap is possible, but now you need to have a DMM synchronised to 
the measurements. Possible, but a little more complex.

Cheers,
Magnus

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