[time-nuts] Frequency Counter Choice

[pe1rks]

Gents, 

In the manual there is no mention of a calibration jumper and I can't
find any inside the counter. 

New battery, power cycle, reset etc. no joy. 

Maybe some secret sauce to get to the 61 characters? 

Stijn 

Rex schreef op 2020-11-12 02:05: 

> Stijn,
> 
> Sorry to hear writing the string I read out hasn't worked so far.
> 
> Magnus,
> 
> Earlier in this thread (date 11/9) you said, "In order to write, you
> need to move the calibration jumper inside."
> 
> Do you recall, is there any truth to that? I only saw it mentioned in
> that one message and I thought maybe you were thinking of the
> Unprotect command (:SYST:UNPR;) that must precede the PUD write.
> 
> I'm not sure I really understand all the concepts of the process that
> the PC program drives to find the CALPLS parameter. If it actually
> iterates through many values of this parameter to make the tests, then
> there must be a GPIB way to set it without a power cycle. I'm just
> speculating.
> 
> -Rex
> 
> On 11/11/2020 6:23 AM, Magnus Danielson wrote: Stijn,
> 
> Have you tried to power-cycle your counter?
> 
> May seem like a silly question, but just to make sure we are on the same
> page.
> 
> I have had similar problems, but did not debug them all. I do remember
> that after writing the string successfully I had to power-cycle the
> counter thought, before it got accepted and past Calibration Lost message.
> 
> When I did this I could not rule out that my programming to control the
> USB-GPIB infterface was correct, as I bone-headidly wrote my own from
> ground up. At the time all the stuff with GPIB was flimsy so that's why
> I just did not use what was available.
> 
> Cheers,
> Magnus
> 
> On 2020-11-11 11:46, Stijn wrote: Hi All,
> 
> I am one of the lucky persons with a PM6681 that has lost it's
> calibration parameters.
> 
> Unfortunatly it seems not as simple as sending: :SYST:UNPR; *PUD #261
> CALIBRATED: 2006-11-07, CALPLS: 4.25 ns, TMP: +22 °C
> This produces an error.
> If I sent: :SYST:UNPR; *PUD #253 CALIBRATED: 2006-11-07, CALPLS: 4.25
> ns, TMP: +22 °C
> Then the counter accepts the string and stores it.
> 
> BUT, I still get the Calibration Lost message.
> 
> btw. the LF at the end of the string you receive from the counter is
> added by the counter itself, so it does not count for the charactercount.
> 
> I do have a different firmware version: PHILIPS, PM6681, 0, MAIN
> V1.05  27 Jan 1997 / GPIB V1.13  27 Jan 1997
> 
> Stijn
> 
> Op 09-11-2020 om 17:47 schreef Rex: Magnus and Azelio,
> 
> (About Pendulum or Fluke or Philips PM6681 Counter or equivalent CNT-81)
> 
> Here's a link to the thread where Magnus shared info in 2015.
> https://time-nuts.febo.narkive.com/6WTFfsyN/pm6680-or-53131a-for-timepod
> 
> Your post is about half way down -- 2015-11-18 22:18:04 UTC
> 
> Yesterday I dug out my GPIB-capable PC and sent a couple commands to
> my Fluke PM6681.
> 
> First I tried a basic one:
> *IDN?
> and got
> PHILIPS, PM6681, 0, MAIN V1.09  26 JAN 2001 / GPIB V1.13  26 JAN 2001
> 
> So connection is good. Interestingly the *IDN command description
> says the PM6681 will return its SN but the SN field here is 0. Oh
> well, not important.
> 
> Then I sent *PUD?
> and got
> #261 CALIBRATED: 2006-11-07, CALPLS: 4.25 ns, TMP: +22 °C[LF]
> where the [LF] at the end is not literal, it represents the line feed
> char 0x0a.
> 
> So in addition to the CALPLS value, it looks like they also save the
> TMP in centigrade when the test was run. I wonder if the counter uses
> that?
> 
> So I hope if my counter ever lost this cal value, I could send it
> this command:
> :SYST:UNPR; *PUD #261 CALIBRATED: 2006-11-07, CALPLS: 4.25 ns, TMP:
> +22 °C
> 
> I don't plan to try that now. If it ain't broke don't fix it.
> 
> There is one odd thing I see though. The last two of #261 is supposed
> to say the string length is 61. But it isn't. I count it as 53 chars.
> I don't know if this matters but the counter gave that number to me.
> In the Programming Manual description page for *PUD, it gives a
> couple examples and the #2nn values shown do have lengths that match
> their string lengths.
> 
> If it is useful to anyone, I made a version of just the *PUD command
> description from the Programming Manual and put it here:
> www.xertech.net/pm6681/PUD_cmd.pdf [1]
> 
> I also made a version of the Interpolater calibration process page
> from the Service Manual. It can't really be used since it is obsolete
> and the old DOS program seems unobtanium. It may give a few hints
> what they were up to.
> I put it here:
> www.xertech.net/pm6681/interpolate_cal.pdf [2]
> 
> So thanks for pointing out that the *PUD command saved string is what
> you lose if the memory backup battery dies. Reading and saving the
> value is what I hoped for and now I've done it.
> 
> If anyone has a PM6681 counter or equivalent with the "Cal.Lost"
> message, sending my string above might be good enough to get it
> working, though maybe not optimum.
> 
> On 11/9/2020 1:58 AM, Magnus Danielson wrote: Thanks for the memory refresh.
> 
> You can read the string using PUD?
> 
> Do that and keep the result. PUD and PUD? is the magic in the counter,
> the rest is software and hardware outside of the counter for
> calibration.
> 
> In order to write, you need to move the calibration jumper inside.
> 
> Cheers,
> Magnus
 

Links:
------
[1] http://www.xertech.net/pm6681/PUD_cmd.pdf
[2] http://www.xertech.net/pm6681/interpolate_cal.pdf