BK Precision 9123A calibration

[Mr Lurpak]

Have anyone tried to or know how to calibrate BK Precision 9123A power supply?

I had to replace like all caps due to corroded pins on them which was causing it to drift like hell. After replacing all caps and cleaning the board it is now very stable but a little off in the calibration/display/settings.

Is cal done via the PC interface or is there a hidden menu?

Cheers

[Kean]

I suspect it is similar to the triple channel BK 9130 which requires PC software, or use of "undocumented" SCPI commands.  Luckily ITECH (the OEM) did publish some limited calibration docs for the IT6300 series.

The last few comments in this thread give some detail - in particular reply #8 by rniu and reply #9 by Pedrofabian.
https://www.eevblog.com/forum/metrology/bk-precision-9130-itech-it6300-calibration/

The BK 9123A has near identical display and button layout to the BK 9130 (aka ITECH IT6322), but with only one output channel.  So it may use very similar calibration process, but only for one channel.
I am not sure if ITECH also sold a similar single channel supply with two line display under their own model number.  None of the IT6100 series I have seen have the same two line display layout.

[Kean]

Actually, the official BK 912xA user manual does list the calibration commands, which are indeed near identical to the BK 9130/IT6322 ones.
From a quick comparison the 9123A is just missing the CAL:SEC:CODE and CAL:STR commands, and an added CAL:DVM command.

https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/912xA_manual.pdf

You might ask want to ask BK support.  There has been mentions of them assisting with the cal software for some older devices.

[Mr Lurpak]

Thank you, yes I did have a read of the link. I also saw the SCPI in the manual - but was a bit confused as some documents state there is a menu for it. I guess that is for a different/older model.

With this info I managed to get a bit further and accomplished some calibration except for DVM which is a bit of a grey area.

If helpful for others:

1. the program CV9100 doesn't not work with 9123A unsupported commands.
2. However, with the python script (for syntax)  from the link you added and the manual I managed to get "Termite terminal emulator" to connect to the PSU via a Serial TTL to USB and 3 wires from pin 2,3 and 5 (RXD, TXD and GND x-ing the RX/TX). And connected a Agilent DVM to output as shown in the program for reading of the level P1 and P2 (set by Cal command)
3. Then I could use the commands as you suggested


SYSTem:VERsion?      (mostly to check if coms works see screenshot I found on BK precision webpage and used)

CALibration:SECure:STATe OFF,"9123";:syst:err?   (9123 is PIN for protecting CAL - guessed until it returned 0 indicating unlocked, but try 0000, 1234 etc.)

CAL:VOLT:LEV P1;:syst:err?

cal:volt 1.01678;:syst:err?     (value is what you read on the EXT DVM with this accuracy)

CAL:VOLT:LEV P2;:syst:err?

cal:volt 36.034;:syst:err?

cal:sav;:syst:err?     (save it )

CALibration:SECure:STATe ON,"9123";:syst:err?   (Lock Cal again with known code)

Current was spot on so need for that and DVM hmmm not really documented - but at least I have a fairly accurate PSU now. So good for now - thanks all.

Ohh BTW I had some weird readings after cal but it was due to I had enabled REMOTE SENSE. TBH BK Precision was not that helpful I did contact them at first hoping for a magic script/program lol but hey-ho that would have been too easy, right?

If anyone has done or have idea on the DVM commands please share.

[Mr Lurpak]

And for the software it looks like it is just a sexy GUI on top of the SCPI commands. 

[Kean]

I didn't think the other calibration software would work, but just that the info there might get you heading in the right direction.  Great that you made sense of it.

No great suggestions on the DVM calibration.  I don't have that feature on my 9130, nor does the documentation provide enough detail.  I suspect you just inject a voltage and tell it what that voltage is.  Probably something close to full scale, so maybe 10V on the 12V range.  Not sure what the levels are, but I'd guess they select range.  You could see if setting different values for CAL:DVM:LEV change the displayed range/mode.  Fiddling with this might just make the readings worse though, but you can probably revert to factory default with CAL:INIT if things get screwy.

Note that you probably should be using an isolated UART connection, or you could damage your computer via a ground loop.  At least that is the case with some other ITECH designs.  The official isolated USB cable is the IT-E132B, but it is a bit pricey.  I don't know why they couldn't include the isolation inside the equipment.

Instead of these expensive cables, you could use one of the cheap USB isolators based on an ADuM3160 along with whatever USB UART interface you already have.  Years ago I bought a couple of the now discontinued IT-E132 which used an ancient PL2303 USB UART chip.  Working drivers for that IC are no longer available, but the IC is mostly pin compatible with an FTDI FT232R so I just swapped those in and removed the unused crystal and load capacitors.  Now I typically use an ADuM3160 adapter or one of the isolated uart adapters from duppa.net.

[Kean]

Oh, it looks like the 9124A manual has a tiny bit more info on DVM calibration than the generic 912xA manual.
https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/9124_manual.pdf

Specifically it looks like you can do 4 point calibration.  No idea if those are for different ranges/modes or what though.
Note that the examples given seem to suffer from copy/paste fatigue.

Code: [Select]

CALibration:DVM:LEVel
This command can set current calibration point. P1,P2,P3,P4.
Command syntax：CALibration:DVM:LEVel <point>
Parameter：P1|P2|P3|P4

CALibration:DVM [:DATA] {<numeric value>}
Return actual output current value to calibration point.
Command syntax：CALibration:DVM [:DATA] <NRf>
Parameter：<NRf>
Example：CAL:VOLT 3.0002A
I found that document by doing a Google search on "CALibration:DVM:LEVel".  The search results also brought up a ITECH IT6100B manual in Chinese... and the translation adds a little more context on top of the BK 9124A manual.  Looks like 4-point voltage calibration you need to do sequentially at different points in the range.  The IT6100B seems to be a newer generation with different display layout, but based on the same firmware implementation.  No other SCPI based devices seem to use the CALibration:DVM:LEVel command.

Code: [Select]

CALibration:DVM: POINt

CALibration:DVM: LEVel
This command specifies the calibration point for the voltmeter. Calibration points P1, P2, P3, and P4 must be calibrated sequentially.

Command Syntax: CALibration: DVM: POINt <point>
Parameters: P1|P2|P3|P4

CALibration:DVM [:DATA] {<numeric value>}
Returns the actual input voltage value assigned to the current calibration point of the power supply.

Command Syntax: CALibration: DVM [:DATA] <NRf>
Parameters: <NRf>
Example: CAL:VOLT 3.0002V