Interfacing the HP3490A with AR488

[Joel_S]

Hello,
I am trying to control an HP3490A DVM from a PC via GPIB with an Arduino-based AR488, using PuTTY as the user interface.
So far, two things already work :
- When the 3490A is in "talk only" mode, measurement data is received and displayed as expected
- When in "addressed" mode, I am able to control the functions of the 3490A (select functions, switch ranges etc ...) as explained in table 3-7, page 3-10 of the 3490A manual.
However, when in "addressed" mode, I cannot receive measurement results over the HP-IB. It seems that the 3490A requires the ATN line to be activated, but the AR488 manual doesn't provide any information on how to do that.
Any help would be appreciated ... the 3490A is a very nice beast !
Thanks,
Joel Setton

[Gertjan]

Did you ask for the answer with ++read?

First you send a command to the DVM to request a measurement, the DVM will take the measurement, and put it in it's buffer. When you send as next command ++read, the buffer will be read, and the answer sent to your terminal progam.

Alternatively you can start with sending ++auto 1 to the AR488. With this configuration command, the AR488 will automatically try to read the DVM buffer after a measurement command is sent.
Read the AR488 manual for the details.

regards & good luck, Gertjan.

[Joel_S]

Hello Gertjan, and thank you for taking the time to respond !

I have done quite a bit of experimenting along the line of your suggestions. I first connected the AR488 to an HP 3457A multimeter, and followed this sequence:
++ mode 1
++addr 12    // this is the HP-IB address of the 3457A
++read
and I receive the reading from the 3457A:
1.0000034E+00

I also used the ++auto 1 command, as you suggested. It worked ! Readings are displayed automatically after each command, for example typing ?[CR] immediately returns the voltage reading from the 3457A.

Unfortunately, this does not work with the 3490A. I can "talk" to it to select various unctions (DCV/ACV/Ohms) and ranges, but I can't get the 3490A to talk back. It is an old instrument, and I understand its handling of the HP-IB is not the same as more recent models such as the 3457A. I'm still trying !

Thanks again,

Joel

[ch_scr]

Have you checked you didn't by accident set the unit to "listener" only?

[Joel_S]

Hi !
I didn't know the instrument could be set to "listener only".
There is a switch on the 3490A rear panel, to select between "Addressable" and "Talk Only".
I set it to "addressable".
When it was set to "talk only", the voltage measurements were received OK by the AR488 and displayed by PuTTY, but of course I could not control the instrument.
When set to "addressable", I can control the instrument (selecting DCV / ACV / Ohms, ranges, etc...) but measurement results are not received by the AR488.

Joel

[Gertjan]

Hi Joel_S,

Good to hear that your AR488 setup is working fine with the HP 3457A. This indicates that your GPIB setup is working without issues.

The solution to solving GPIB problems with another meter (in this case your 3490A) is almost always studying the meter's manual in detail.

Do you end your command strings to the 3490A with "E" (for "Execute")? This was usual in the command language for old meters. Every command string had to be ended with an execute command. "E" for the 3490A. Without the "E", the 3490A will do nothing, just waiting for more commands....

So, to get a reading I would try command strings like these:
T1E (Immediate trigger, Execute)
M1E (Take reading when triggered and output the reading when addressed to talk, Execute),

Playing with command strings like these, with the manual next to the keyboard, will make you learn how to communicate with the meter.

regards, Gertjan.