[time-nuts] Question about frequency counter testing

[Tom Van Baak]

> That might be an interesting way to analyze TICC data.  It would work 
> better/faster if you used a custom divider to trigger the TICC as fast as it 
> can print rather than using the typical PPS.

Hi Hal,

Exactly correct. For more details see this posting:
https://www.febo.com/pipermail/time-nuts/2014-December/089787.html

That's one reason for the 1/10/100/1000 Hz PIC divider chips -- to make measurements at 100PPS instead of 1PPS.

JohnA could have designed the TAPR/TICC to be a traditional two-input A->B Time Interval Counter (TIC) like any counter you see from hp. But instead, with the same hardware, he implemented it as a Time Stamping Counter (TSC) pair. This gives you A->B as time interval if you want, but it also gives you REF->A and REF->B as time stamps as well.

You can operate the two channels separately if you want, that is, two completely different DUT measurements at the same time, as if you had two TIC's for the price of one. Or you can run them synchronized so that you are effectively making three simultaneous measurements: DUTa vs. REF vs. DUTb vs.

This paper is a must read:

Modern frequency counting principles
http://www.npl.co.uk/upload/pdf/20060209_t-f_johansson_1.pdf

See also:

New frequency counting principle improves resolution
http://tycho.usno.navy.mil/ptti/2005papers/paper67.pdf

Continuous Measurements with Zero Dead-Time in CNT-91
http://www.testmart.com/webdata/mfr_promo/whitepaper_cnt91.pdf

Time & Frequency Measurements for Oscillator Manufacturers using CNT-91
http://www.testmart.com/webdata/mfr_promo/whitepaper_osc%20manu_cnt91.pdf

Some comments and links to HP's early time stamping chip:
https://www.febo.com/pipermail/time-nuts/2017-November/107528.html

/tvb