Philips Fluke PM6680 PM6681 CNT-81 Frequency Counter Calibration Setup - Page 1
Forum section: electronics / repair

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: July 01, 2020, 02:08:05 pm
content: I've got a counter with gone calibration constants and possibly wrong firmware.I hope there is somebody out there that has a counter and E-PROM programmer handy to make a copy.A bit harder I guess is to make a copy of the constants for the cal... but maybe somebody already made a copy, would be great.Also.. I've already placed add in the WTB section but I would like to buy another one of those counters to check on ASICs, my counter is reporting error 2.Or maybe somebody has a physically broken one.. screen, case, that I can have, to harvest guts from to fix mine.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: July 01, 2020, 04:53:50 pm
content: The firmware I have in mine is PM6681 rev15 v.1.09.I was wondering if it's normal to have the 6681 firmware in 6680... is there any difference in functionality.My counter is PM6680 not a B version, my GPIB is on the mother board, not separate board.

author: BU508A
author_rank: Super Contributor
timestamp: July 11, 2020, 07:46:13 am
content: Hi,I've uploaded the firmware from my 6681 here:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2871844/#msg2871844There you can find also some pictures.I'm not sure, if there are some calibration constants exist, because the adjusting will be done by tweaking some trimpots.

author: cherrylee
author_rank: Contributor
timestamp: August 10, 2020, 02:30:11 am
content: I have a PM6681R,if you remove the battery,the calibration data of the machine will be lost.I checked the official manual and there is a tool: CALVER81, but I did not find it anywhere

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: August 10, 2020, 04:31:06 am
content: Yes, the software is nowhere to be found. Would be nice to actually find it somewhere... I’m pretty sure somebody has a copy.It’s an old DOS piece of software.There is also a discussion about *PUD command used to write the constants from the calibration routine into the memory of the counter but I can’t find an actual command line.I would be happy to just guesstimate the constant or copy it over from some other counter.Yes, when changing battery keep you counter powered on. The lifespan for the battery is estimated at between 5 to 10 years.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: August 10, 2020, 05:15:08 am
content: Here is a note from Fluke:Calibration Adjustment for PM6680 & PM6681Christopher BaileyDecember 19, 2016 15:24The CALVER80 and CALVER81 programs are no longer available for download. The equipment required to run these programs is obsolete and no longer supported by its original manufacturer.Fluke still supports the Fluke and Phillips models PM6681 and PM6681R.https://support.flukecal.com/hc/en-us/articles/115000074083-Calibration-Adjustment-for-PM6680-PM6681-

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: August 10, 2020, 05:22:18 am
content: And here is some info from a post in 2018... from user crasyboye at:http://bbs.38hot.net/thread-258164-1-1.htmlSome information found abroad, but did not mention anything too substantial.The original PM6681 calibration setup includes a PC, anancient Philips ISA-bus GPIB interface and an ancient Philips driver and a DOS program.Collecting these and put them together to work will be an interestingchallenge.A more modern variant of the calibration routines run can run on moremodern HW and LabView software. Philips PM5781 and Agilent 81112A pulsegenerators is supported by those routines.By now the production of the counter has stopped, as the counter coreASIC ran out of stock.The folks who designed and maintained them does not work there anymore.Turns out the core setup requires a generator that creates a skewedSweep over that you SUCH Frequency at The interpolation Phases. TWEAK by Youat The Calibration value (3.86-4.50 ns 0.02 ns in Steps) you that the SET overGPIB at The * PUD a using the Command. by You CAN IT Yourself a using the Check * PUD? .It Sweeps over the this range and checks for the value giving lowest RMSvalue (SDEV result) and then sets this as the final value.You can set the value using the command :SYST:UNPR;*PUD %s where %s isthe string, looking somewhat like this:FACTORY CALIBRATED: %s%s, CALPLS 3.98 nsThe two %s in there is for some string and date, I just don't bother todig up a correct example.Anyway, you can actually read-out the data and write it back without thesoftware. It should be possible to do something with the existing piecesand it might be possible to actually get the calibration softwareoperational again.I just don't have a CNT81 anymore to try this out on.With the hints from the former Pendulum service guy, I havestarted towrite my own code in order to restore calibration on a CNT-81/PM-6681.This have been a discussion on and off for a couple of years, so I endedup buying a PM-6681 which had the Loss of Calibration message " CALLOSS".First things is to replace the CMOS battery, which is a trivial thing toreplace the CR2032 battery, had one laying around.Then, I've been digging into the NI VISA files, which have snippets ofactual code in it. As I don't have NI VISA and not running with myPrologix, I was a bit out of luck there. So I had to start from theground up, taking a serial interface hack I already have, write someminimalistic Prologix support for it (TvB hp59309.c provided some neededclues on how to get it working stable).Then more and more bits and pieces have been falling together, likebeing able to build and write the *PUD string. Also, triggering thecalibration itself and using an external source.Now my counter does not display the error anymore and seems to behavemore coherently. I'm not completely trusting it, as I am not doing thefull sweep over calibration pulse calibration values ​​and measuring theireffect, that will be part of the complete solution, but at least I getsufficient part of the way.Far from bullet-proof, it is however worth celebrating these baby stepsin the right direction.

author: cherrylee
author_rank: Contributor
timestamp: August 10, 2020, 07:54:45 am
content: Yes, I tried the calibration command in the service manual, but it was unsuccessful;this machine also has a bug. When the rubidium clock heats up to a certain degree under low temperature operation, the fan will stop rotating and cannot start again.

author: cherrylee
author_rank: Contributor
timestamp: August 10, 2020, 07:56:16 am
content: Someone tried to contact Fluke to calibrate this instrument, but the calibration cost was too high, enough to buy a new machine with better performance

author: coromonadalix
author_rank: Super Contributor
timestamp: August 10, 2020, 05:28:24 pm
content: check ??maybe some folk(s) is registred there ?http://bbs.38hot.net/thread-258164-1-1.htmlAnd a service manualhttps://ia800203.us.archive.org/1/items/FLUKE_PM6681_Service_Manual/FLUKE_PM6681_Service_Manual.pdf

author: cherrylee
author_rank: Contributor
timestamp: August 11, 2020, 05:19:25 am
content: Who has TimeView software that supports PM6681?I saw the software description in the manual.http://www.testequipmenthq.com/datasheets/PENDULUM-CNT-81%20(FLUKE%20PM6681)-Datasheet.pdfHowever, Pendulum's official version is a paid version, and it does not support PM6681.

author: FransW
author_rank: Frequent Contributor
timestamp: August 11, 2020, 08:04:48 am
content: Here it is specified:http://www.ezutech.com/Pendulum_product/catalog/CNT81_81R.pdfUsermanual:If you have a CNT-81, you can use TimeView for probe compensation. See the TimeView chapter of this manual.https://physics-astronomy-manuals.wwu.edu/Fluke%20PM6680B%20Timer%20Counter%20Operators%20Manual.pdfIf you have a PM6681, you can use TimeView for probe compensation. See the TimeView chapter of this manual. Using the controls. 2-12 Rear Panel. Probe.Edit: URL's

author: cherrylee
author_rank: Contributor
timestamp: August 12, 2020, 01:17:31 am
content: The manual describes that this machine has a supporting floppy disk, which contains all the software.but I have not seen it on the Internet, maybe the software has been permanently lost.

author: cherrylee
author_rank: Contributor
timestamp: August 12, 2020, 01:21:28 am
content: Maybe I should give up CNT-81R and use other products .like CNT-91, HP53132, HP53220, etc.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: August 12, 2020, 02:20:29 am
content: I'm pretty sure somebody out there has a disk or a copy stashed away in some dark corner... question of time.... or Fluke service department showing mercy and sharing it with the world ... again.

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: May 15, 2021, 10:46:13 pm
content: It's been a year and I finally found the software.For every ones benefit and enjoyment I'm pleased to presentCalver81....Would be great to have some advice on how to build a system to calibrate those..Anybody having suggestions, please, please join the conversation.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 16, 2021, 03:33:42 am
content: maybe using thehttps://www.eevblog.com/forum/projects/ar488-arduino-based-gpib-adapter/could work ??

author: Testtech
author_rank: Regular Contributor
timestamp: May 17, 2021, 11:11:15 pm
content: Thanks for sharing!

author: cherrylee
author_rank: Contributor
timestamp: June 21, 2021, 07:10:24 am
content: thankyou ！

author: Stijn
author_rank: Newbie
timestamp: June 21, 2021, 09:13:40 am
content: More info about calibration is to be found at:http://www.leapsecond.com/museum/pm6681/Calibration is done using some undocumented commands::DIAG:CAL:INT:COUNT 260000:DIAG:CAL:INT:AUTO ONCE:DIAG:CAL:INT:SAVE:DIAG:CAL:INT:RECALL:SYST:TIME:POW?:SYST:TEMP?

author: picburner
author_rank: Frequent Contributor
timestamp: July 16, 2021, 05:10:08 am
content: Where can I find the Labview application IPOLCAL (IPOL.vi) mentioned in the archive calver81.zip which allows also to use an HP 8110A pulse generator?I don't have a Philips PM5781 unfortunately!

author: picburner
author_rank: Frequent Contributor
timestamp: July 28, 2021, 02:05:56 pm
content: The calver81.exe program works under Windows7 x86 also as you can see from the attached pics.An old PC with an ISA PCIIA card is not essential, I used a notebook with an NI pcmcia gpib card.I was able to complete the calibration and make sure that the PM6681 no longer presents the "CAL LOST" error message.Of course, not having a PM5781, I had to trick the program by temporarily modifying the identification string of another instrument.I ordered an HP 8110A as it is practically impossible to find a Philips PM5781 and when I get it I will write a program in Pythonable to calibrate the instrument for serious this time. For now I have only removed the "CAL LOST" error message.