Problem with HP53131A Universal Counter and GPIB

[marshri]

I am trying to write a simple program to read the measured frequency on the 53131A counter. The problem is that when the counter is operating in GPIB remote, the instrument will not show the last three or four digets past the decimal point. If not in remote mode, the instrument will show all the digets it is capable of. Example, if I feed it a 1.2343212 MHz signal, when in GPIB mode, I will get 1.234000+6 back. The display on the instrument will show 1.234***Hz. LabView is collecting what is displayed on the front of the counter and sending to the computer. I have already tried adjusting the format&precision of the indicator. I wish it were just that easy. I have been using the HP programming manual that came wiht this ins
trument and have found the commands that control the display. Unfortunatly, I cannot find out how or why the instrument is replacing the last four digets with asterisks. I need to solve this problem so that I can finish the program. If anybody has had this or a similar problem with HP equipment I would greatly appriceate some advice.

Thanks to all those who respond

marshri

[Ray.R]

How many digit precision do you get when running your vi?

The asterisks may only appear to indicate that you are in remote mode. The precision shouldn't change. Have you tried displaying a reading from a vi? Then press the "Local" button on the instrument (actually the other feature of the "Save & Print" button), and compare the readings.

Unfortunately, my frequency counter is not yet hooked up to the GPIB card, so I cannot test out a vi.

-JLV-

[Dennis_Knutson]

There is a DIGITs command that sets the resolution. After a reset, the instrument is set for 4 digits I believe. You should be able to find the command in the manual in the :Sense subsystem. I use :SENS:FREQ:ARM:STOP:DIG 6 to set my counter for 6 digit resolution on frequency measurements.

[marshri]

Thank you for your input, but shortly after posting my message this morning, a colleague and I solved the problem. I used ":MEAS:FREQ? 50 MHZ, 1 HZ (@1)". This may not be the best method but it works and for a green horn like me I feel pretty good finding this one.