Low Cost PCB's Low Cost Components

Author Topic: Calibrating 53132A  (Read 1394 times)

0 Members and 1 Guest are viewing this topic.

Offline JohnPi

  • Contributor
  • Posts: 17
  • Country: us
Calibrating 53132A
« on: September 22, 2017, 02:18:03 PM »
I have an external OCXO and wanted to use it to calibrate my 53132A. However, after I successfully calibrate, the 53132A then reads
10.000 000 002 4 or so. It is not that it is measuring the offset of the OCXO, but when calibrated (using the internal CAL: TIMEBAS capability) with a stable signal (visible dither is about +/- 3 counts in the last digit), but when measuring the exact same signal that it was just calibrated with, it reads high by a noticeable amount.

Has anyone else noticed this on their counter ?
 

Offline awallin

  • Frequent Contributor
  • **
  • Posts: 343
Re: Calibrating 53132A
« Reply #1 on: September 22, 2017, 02:53:32 PM »
If you split the 10MHz from the OCXO both to the Ext Ref at the back and into an input channel you should get an accurate number, with a spread corresponding to white phase noise that can be calculated from the counter specs.

For the 53230A the single-shot spec is 20ps for time-interval but in practice it does around 11-13ps, and that corresponds to an ADEV of around 2e-11 at 1s.
So with a 1s gate time, and the above setup with the same 10MHz to Ref and CH1, you'd expect values around 10MHz with a standard deviation of 2e-11 * 1e7 Hz =  200 uHz.

If you disconnect your OCXO from Ref and only connect it to CH1 it depends on the quality of the internal and external OCXO, you'd probably see a drift of maybe 1e-9 per day between the two OCXOs.

Anders
 

Online HighVoltage

  • Super Contributor
  • ***
  • Posts: 3268
  • Country: de
Re: Calibrating 53132A
« Reply #2 on: September 22, 2017, 11:10:06 PM »
You need to repeat the calibration procedure a few times and with each time it gets closer to the nominal value and then it will stay stable.

I have noticed this requirement on my 53132A and 53131A counters.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline texaspyro

  • Frequent Contributor
  • **
  • Posts: 387
Re: Calibrating 53132A
« Reply #3 on: September 22, 2017, 11:19:03 PM »
The 53131/2 counters use a 12 bit DAC to set the OCXO EFC voltage.   Depending upon your OCXO this gives a tuning accuracy of 1-2 mHz.  Also, the tuning algorithm does basically a binary search of the EFC word to find the DAC value that puts the OCXO on freq.  It starts with measuring the OCXO at min and max EFC words and refines the DAC value over a period of around 3 minutes.  The initial min/max voltage swing can disturb the OCXO enough so that the OCXO later drifts further off frequency.

On the subject of HP-531xx counter calibration...  the calibration of the counter time interval measurement can be either a crude "quick" mode or a sophisticated "fine" mode.  The quick mode just does a measurement of channel A.  The "fine" mode does four measurements between channel "A" and channel "B".  The fine cal requires a high dollar pulse generator and a rather unobtainum HP-59992A J06 time interval calibrator.

Calibrating the channel gains requires a precise 5V source.

I have designed a board that replaces the pulse generator / HP-59992A.  It also has a precise 5V reference for the channel gain cal.   The time interval calibrator requires a high quality 10 MHz input signal (seems to work well with the 10 MHz output of the counter if it has the OCXO timebase).

The time interval calibrator works by squaring up the input 10 MHz signal,  digitally multiplying it up to 20  MHZ,  dividing it by two into complementary 10 MHz signals,  buffering the outputs and level shifting them to 1V p-p, and routing various combinations of the true and complemented signals to the output BNC connectors.  These correspond to the 1/2/3/4 buttons of the J06.

I plan to sell a kit (or possibly assembled units).  I have parts and boards for 50 units on the way...
Hopefully the cost will be under $30.
« Last Edit: September 22, 2017, 11:44:31 PM by texaspyro »
 
The following users thanked this post: CalMachine

Offline texaspyro

  • Frequent Contributor
  • **
  • Posts: 387
Re: Calibrating 53132A
« Reply #4 on: September 22, 2017, 11:39:40 PM »
I put one of Gerry Sweeny's OCXO boards in my 53132A.  I used a UCT 8663 OCXO.  I originally had the board set to the 0 .. 10V output range.  The EFC sensitivity of the OCXO was around 0.75V / Hz and the best the timebase autocal could do was around 2 mHz.   The OCXO was on freq with a 4.5V EFC voltage.  I changed the OCXO board to 0 .. 5V and the autocal got the OCXO to around 1 mHz.

Over a month of continuous operation the OCXO drift rate settled down to less than 1 mHZ/day, but I was doing the autocal every day.   After the initial month I did an autocal and did not change it for another month.  The OCXO had drifted less than 1 mHz.

The reason I did the calibrator board was my 53132A came with early firmware that did not put commas between groups of three decimal points... very annoying to use.   I upgraded the firmware to a much later version (ROM images are on the forum somewhere),  but the firmware upgrade requires a full calibration.   A member of the time-nuts list sent me a J06 for the cost of shipping from Australia, so I really didn't need my board... but I had already designed it and figured that other people would find it useful.  HP has an ap-note that shows how you can use it to improve time interval accuracy for any counter.
« Last Edit: September 22, 2017, 11:41:15 PM by texaspyro »
 

Offline JohnPi

  • Contributor
  • Posts: 17
  • Country: us
Re: Calibrating 53132A
« Reply #5 on: September 23, 2017, 12:31:57 AM »
I'm using Gerry Sweeney's OCXO also; I think it has a Trimble OCXO which is good.

A problem with the external OCXO I have is that it is unbuffered. the freq. shifts ~ 100 mHz when using a 50 ohm load vs not using one. Perhaps the 53132A is changing its internal 50 ohm on & off ? I plan on building a low noise buffer for my OCXO and will try with that.
 

Offline texaspyro

  • Frequent Contributor
  • **
  • Posts: 387
Re: Calibrating 53132A
« Reply #6 on: September 23, 2017, 12:44:40 AM »
Theoretically you can get better performance with OCXO boards that use a pot to set the frequency than the DAC.   But that means you need a VERY stable (time and temperature wise) EFC reference voltage and pot (plus probably some range limiting resistors).  Probably not an easy thing to achieve in the real world.  If I did that, I would mount the pot on the OCXO board so the adjustment screw could be accessed through a hole drilled in the case to that you could adjust it without opening the case and messing up the thermal environment.

I've put a lot of 8663's into counters like the Tek DC5010.  The 8663 has a nice reference voltage output.  I used some very stable pots that I glued to the OCXO case with thermal epoxy.  That worked rather well.
 

Offline Tony_G

  • Frequent Contributor
  • **
  • Posts: 299
  • Country: us
Re: Calibrating 53132A
« Reply #7 on: September 23, 2017, 01:12:49 AM »
I plan to sell a kit (or possibly assembled units).  I have parts and boards for 50 units on the way...
Hopefully the cost will be under $30.

Please add me to the mailing list for when you go live with it - I'll happily buy a kit for this (in fact I might get two).

TonyG
 

Offline JohnPi

  • Contributor
  • Posts: 17
  • Country: us
Re: Calibrating 53132A
« Reply #8 on: September 23, 2017, 11:52:30 AM »
I'll take one too.
 

Offline carl_lab

  • Frequent Contributor
  • **
  • Posts: 378
  • Country: de
Re: Calibrating 53132A
« Reply #9 on: September 24, 2017, 03:15:06 AM »
I plan to sell a kit (or possibly assembled units).
Are you willing to publish the circuit diagram?
 

Offline texaspyro

  • Frequent Contributor
  • **
  • Posts: 387
Re: Calibrating 53132A
« Reply #10 on: September 24, 2017, 09:24:59 AM »
It looks like the pinouts of the rotary switches that I received do not match the sample... bastards!  Looks like I may need to re-spin the PCB.
 

Offline ManateeMafia

  • Frequent Contributor
  • **
  • Posts: 631
  • Country: us
Re: Calibrating 53132A
« Reply #11 on: September 24, 2017, 10:34:53 PM »
I am interested in one.
 

Online HighVoltage

  • Super Contributor
  • ***
  • Posts: 3268
  • Country: de
Re: Calibrating 53132A
« Reply #12 on: September 24, 2017, 11:17:04 PM »
I am also interested in one of your kits
There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline texaspyro

  • Frequent Contributor
  • **
  • Posts: 387
Re: Calibrating 53132A
« Reply #13 on: October 01, 2017, 02:06:22 PM »
A quick update on the time interval calibrator board...   the Chinese board house has finally shipped the boards DHL express (I think they mis-placed the original order).  Should be here in a few days, US customs is apparently giving everything from China a triple, un-lubed body cavity search looking for drugs.  But, I'm 99% sure I need to re-spin the board to match the pinouts of the rotary switches that I received vs the original samples I got in... grrrr...

I found a local assembly house and a couple of people willing to do assembly.  It will probably raise the cost $5-$10 over a kit, but it does allow me to do some testing on them.  Setup costs for small quantity SMD assembly are a bitch.
 

Offline ChuckDarwin

  • Contributor
  • Posts: 13
  • Country: mh
Re: Calibrating 53132A
« Reply #14 on: October 04, 2017, 06:20:58 AM »
Interested, add me to the list, please.
 

Offline texaspyro

  • Frequent Contributor
  • **
  • Posts: 387
Re: Calibrating 53132A
« Reply #15 on: October 09, 2017, 05:32:31 PM »
An update on my HP-531xx calibrator board:

The boards finally arrived!  The board house I use in China normally take 7 to 8 days to get boards into my hands.  This time it took 3 weeks... grrrr.

Anyway, as expected, I need to re-do the boards to match the rotary switches that I got in.  I built one up and bodge wired the switch in... SUCCESS!  I ran the calibration routines on my 53132A and all steps passed the first time.
 

Online sarel.wagner

  • Contributor
  • Posts: 41
  • Country: za
  • Cooking up an Electronix Storm
Re: Calibrating 53132A
« Reply #16 on: October 10, 2017, 01:07:42 AM »
Need one, please add  :clap: :-+

Offline gab_au

  • Newbie
  • Posts: 3
  • Country: au
Re: Calibrating 53132A
« Reply #17 on: October 10, 2017, 07:31:54 PM »
Hi all, (newbie here)
Add me to the list of those interested in a time interval fine calibration module.

A question on that module, I don't see any ECL in the overlay, only HC, or is this only from the library used to create the pcb but you're looking at using fast 3.3V logic equivalents such as the AUC family or AVC or ALVC?  I ask as I would have thought the 8130A and 59992 suggested by the manual would have edges much faster than HC logic? Would that have any effect on the fine cal?

While I'm here I'm wondering if anyone can help with an issue I have with my 53132A.......

I was (am) looking at a homebrew 12.4GHz frequency extension and I tried  to change a few eeprom values that have been posted in a yahoo group. In replacing the eeprom with a socket I managed to corrupt (erase?) the eeprom and lost all data. I was able to recal, except for the time interval fine, and when I put in the modified values to supposedly enable the 12.4GHz module divide ratio I still get a divide by 128 no matter what value is in the 3 eeprom locations. After I recal'd those 3 locations had FF in them.

So I'm thinking one of three things, 1) when I erased the eeprom I lost some critical info, or 2) not only does the eeprom need changing but the software also needs to change to enable the 12.4GHz module or 3) there's more to it than that and the fpga also needs to change, but that seems overkill to change the divide ratio from by 128 (for the 3ghz extender) to divide by 512 (for the 12.4ghz extender). I tried all four possible code0, code1 combinations and got two which gave divide by 128 and two which gave no channel 3.

Would anyone have an eeprom dump that they could share so I can compare what I have now to what a factory eeprom should look like? My unit is a no option unit from the factory.

Has anyone had success in incorporating a non factory 12.4Ghz extender that uses a divide by 512 ratio into a no option counter?

Thanks
Greg
 

Offline dr.diesel

  • Super Contributor
  • ***
  • Posts: 1958
  • Country: us
  • Cramming the magic smoke back in...
Re: Calibrating 53132A
« Reply #18 on: October 10, 2017, 10:25:04 PM »
Add me to the list, one board please. 

Offline texaspyro

  • Frequent Contributor
  • **
  • Posts: 387
Re: Calibrating 53132A
« Reply #19 on: October 11, 2017, 05:09:36 AM »
A question on that module, I don't see any ECL in the overlay, only HC, or is this only from the library used to create the pcb but you're looking at using fast 3.3V logic equivalents such as the AUC family or AVC or ALVC?  I ask as I would have thought the 8130A and 59992 suggested by the manual would have edges much faster than HC logic? Would that have any effect on the fine cal?

The output buffer is a 74AC244 and produces signals with a rise time of less than 1 ns (which gets degraded to around 2ns through the switch and cables).  The actual rise time and duty cycle is not all that critical since the calibration firmware uses various combinations of the P1/P2, P2/P1, N1/N2, N2/N1 measurements to null out all the various offsets and differences.

The cal routine measure the signals at the zero crossing so the rise time is not all that critical as long as the signals are stable over the measurement interval.

This HP product note describes how it is done.  Note that the server seems to be slow and flakey lately:
https://rubidium.dyndns.org/~magnus/instruments/hp/J06-59992A/Better_than_100_ps_Accuracy_in_HP_5370B_Time_Interval_Measurements_Through_Bias_Error_Reduction.pdf

This is the manual for the J06-59992A:
https://rubidium.dyndns.org/~magnus/instruments/hp/J06-59992A/J06-59992A.pdf

And the patent:
https://rubidium.dyndns.org/~magnus/instruments/hp/J06-59992A/US4627268.pdf
 
The following users thanked this post: edavid, gab_au


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf