HP-IB-Command for vintage multimeter

Michael:

The HP 3438A cannot be programmed over the HP-IB. You can only read data from it.

I have a manual for this machine, which I got from

If you have an interest in this machine, you might want to check that Web site.

The format of the data from the HP 3438A is a single line terminated with a carriage return and line feed. The format of this line is as follows:

+D.DDD E+D, F

In this line, the D.DDD is the data display. E+D is the exponent and its value, and F is what function is being read. The values for F are:

1 DCV 2 ACV 3 DCI 4 ACI 5 Ohms.

The string for an Overload Indication is: 1.DDD E+9, F

Aidan Grey

Hello Adrian,

thnak you for your answer.The multimeter is quite easy to use (not as the newer models with special functions) so I can use it without manual. Could you tell me, how many commands are necessary to get a set of data from the HP3438A ? Do I need to adress and de-adress the multimeter or do I only need to send the "get value" string? And what are these strings?

Regards, Michael

Michael:

There don't seem to be any specific commands as such. Just address the multimeter to talk.

If the HP3438A is put into Remote mode, then it requires a "trigger" command before it will take a reading and output it.

I don't know what hardware and software you are using, so I can't give you more specific advice. If you have a GPIB/HPIB monitoring utility, then that might be the easiest way to access the multimeter.

The following is a program listing from the manual, in HPL (I think). Take a look and see if it helps.

10 CMD "?U" 20 FORMAT B 30 OUTPUT (13,20) 1024; 40 CMD "5W" 50 DIM A$[13] 60 ENTER (13,20)A$ 70 PRINT A$ 80 GOTO 60 90 END

The above would continually read from the HP3438A and print the result.

Aidan Grey

Michael How do you interface the meter with the computer? I have an old HP7475 plotter with an interface card that interfaces the HPIB with the old style of computers. Today you can't find that black connector on the new mother boards.

Vlad

You need a HPIB/GPIB interface - probably a newer one. National Instruments and Agilent sell both PCI cards, USB-GPIB and LAN-GPIB convertors. Not so cheap though. The standard command API for GPIB I/O is VISA, which also works with VXI. The basic instructions are similar to the HP BASIC examples above only with a C-like flavor (vprintf, vscanf, instead of output, enter). You'll also need the GPIB command set for the 7475A, which is, fortunately, simply HPGL (old school not HPGL2 or its newer variants).

MM

Do research at

You will find that their cards come in several flavors, AT bus and PCI. PCI cards are considerably more expensive, but do have a chance of being supported under windows XP. Check also what drivers you have. There are some early GPIB-AT cards that are not supported under their 488.2 software, and only have 488.1 compatibility. That requires a program that runs solely under DOS, which if you're happy with it, is fine.

HPIB cards are frequently found on ebay. Search for HPIB and also IEEE-488. Don't forget the cables, either.

There are also some standard kinds of commands that the HP plotters will recognize, ID, RST, etc for the instrument itself.

The type of program interface depends also on what level of language interface you use (high or low level) and what language you program in (Delphi, C++, or Basic).

Harvey

Hello Adrian,

Thanks for the code example. Light at the end of the tunnel :-) Currently I'm using the Labview 7.0 Evaluation Versoin with Windows 2000.

I tried to send the Commands ?U and 5W to the multimeter and the "listen"- LED ligths up.

When I adressed it to talk.the "talk"-LED lights up but the multimeter times out.

I don't have an HPL or HP-Basic manual, so I don't know what the OUTPUT (13,20) 1024; does or how it can be translated to a text version for sending with GPIB-Write.

Are there more informations about the trigger command? Do I need to send a GET (group execute trigger)?

Michael