Electronics > Metrology

Prema 6048 teardown

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--- Quote from: dietert1 on May 18, 2023, 07:52:18 am ---Just found a little trap while nulling the instrument. When you press the null button, you can hear the polarity relay without any delay. Seems they assume you already had the input short for some time and there is a valid null measurement for the current polarity. So they switch the relay to acquire the null reading of the other polarity. With long integration times, if you insert the short and press the null button you may get "Error 4" if the last valid reading is outside limits, like open inputs.

--- End quote ---
I accidentally just stumbled into this nugget, dieter1. Very insightful - I've ran into this many times and had no idea what may cause it. I always thought my meter has some sort of low level issue that's rearing its head once in a while (like caused by some minor leakage, or some data being a bit off somewhere, etc.). I always just sort of shook it into nulling by changing the integration times, range, etc. until it'd be willing to null.

I am registering some success connecting to my 34401A via RS232. I have not yet been able to make GPIB work yet under any of my meters and any of the programs I tried. I mention this because these are my baby steps on this pursuit. I am cursorily controlling my Audio Precision System One via APIB/USB, but that's a whole different story (that's an actively maintained solution).

I think some of you have been able to connect to the Prema via GPIB. Can you offer some guidance? If worth a different thread, I'd be happy to start one.

I am currently doing some pretty extensive monitoring of a bunch of references - a Fluke 931B, 5440A, a VREF10-001 r9, etc. - the first two displaying incredible accuracy and stability (I've been watching last night, overnight, and this morning the 931B being within something like .02ppm of Prema's 9.9999990V... This is in an unconditioned garage, though the weather here is aways very mild. And the 5440A is in the same ballpark, both comfortably within less than about .5ppm of 10.0000000V for some weeks of observations now, under good discipline of performing INT CALs on the 5440A and "zeroings" on the Prema; the 931B needs no such fluff!).

It'd be great if I could log these by monitoring them automatically.

Yes, i have a similar setup logging a Prema 6048 and other meters over GPIB. The GPIB interface is DIY based on a STM32 with a USB.
I wrote a very small Win32 app that uses a serial comm device to talk to the USB-GPIB adapter and to cycle the meter(s). Results get written to text-with-tabs dayfiles that are easy to use e.g. with Excel/OpenOffice. Or with some averaging app to reduce a large amount of raw data before.

Initialization (once)
Configue GPIB
   Manual: Connect GPIB cables and USB cable of interface
   GPIB interface setup (open and configure the driver)
   Bus initialization with IFC bus signal
   Bus and device configuration concerning generation and handling of interface
      signal EOI and/or line terminators

Configure P5017
   The 5017 defines the pace of data acquisitionn, others follow using trigger commands.
   Manual: Bus address=8, 30 V DC, 4 seconds
   sprintf_s(cBuffer,sizeof(cBuffer),"GD %i",iGPIBAddr_P5017);
   iStatus=GPIB_Send(hSerialGPIB,"S0"); // continuous readings

Configure P6048
   Manual: Bus address=7, 20 V DC, 4 seconds
   sprintf_s(cBuffer,sizeof(cBuffer),"GD %i",iGPIBAddr_P6048);
   iStatus=GPIB_Send(hSerialGPIB,"S1"); // single reading, trigger and query result

Data taking loop (reading meters, sending next trigger)
GD 8 OK after 0msec
GQRD? +10.000072E+0MRVDP01A0R3F0T7D0S0Q0M01B00 (44ms)
GD 7 OK after 0msec
GR? +01.0158152E+1MRVDP00A0R3F0T7D0S1Q0MOFB00 (3ms)
S1 OK after 0msec

This is the bus interface dump:
GD n selects a bus device
GQRD? sends the RD? command to query the device and receives its response.
   There is a 44 msec delay until the P5017 terminates its measurement and responds.
GR? reads a response from the selected device
   The P6048 already finished its mesurement and responds quickly
S1 is the P6048 command to trigger and query the next measurement

This is the most basic approach and very reliable. Something similar can also be done using the AR488 interface or commercial GPIB adapters.

Regards, Dieter


--- Quote from: dietert1 on October 10, 2023, 04:16:52 pm ---Yes, i have a similar setup logging a Prema 6048 and other meters over GPIB. The GPIB interface is DIY based on a STM32 with a USB.
Regards, Dieter

--- End quote ---

Thank you very much again, Dieter. Can you elaborate on the GPIB-USB interface? Or, maybe better - if you know - would an NI adapter work? I may have access to one on loan. If this works at all, it seems like it won't be a bank breaker. Unless all those affordable ones are bad clones (I'll take a good clone, though...).

I am using DIY hardware and software for that. For debugging GPIB we have an old HP 59401A.
A beginner should rather look at industrial products. Installing GPIB automation isn't that difficult, once you have the hardware (controller and cables). If you borrow it, you could ask the owner how they used it.
After connecting the hardware (interface and cables) you will download a driver package and install it on a PC. Then you can use an interactive application included with the drivers (e.g. NI "Measurement and automation explorer") and type in commands and talk to your instrument and listen for the response. To automate the process people use data collection applications, see WinGPIB thread. There you can find examples for logging a DVM and use that as a starting point to setup your own process.
GPIB isn't from the AI age. Each instrument has it's own command set. You need to manually assign a different address to each bus device. You need to setup timeouts and EOT convention. GPIB is slow as many of those old instruments have 8 bit MCUs, so each transaction will take some 10 msec or more.
I think i needed about 3 or 4 hours to get the Prema 6048 going - without implementing SRQ though. One nasty "feature" of the Prema is that it forgets the assigned GPIB address on power-down. Maybe that can be solved using the calibration switch.

Regards, Dieter


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