Using a 53131A, How do I detect the condition of no input signal?

[SAW Tester]

Hi,

I am using an Agilent 53131A frequency counter to measure the frequency out of an oscillator.  I need to be able to use the frequency counter to read the frequency when the oscillator is oscillating and indicate when the oscillator is bad (no signal present on the 53131A input).  Does anyone have any suggestions on which type of command I should use?

FETCH?
READ?
MEAS?

The problem I have is in the triggering.  When the oscillator is bad, the counter hangs up as it continues to wait for a trigger which will never come.

Thanks for any help

[JÞB · Accepted solution]

Actually you've gotten right to the solution yourself.  Either you need to revise your triggering scheme or you can use the lack of trigger as your indication.

For instance: you know the measurement will take x seconds to complete if the signal is present.  So you need to determine if the measurement completed in that time.  Simple if you are using GPIB-

1) set the VISA TMO property to be as long as you will wait for the measurement. 

2) Enable SRQ on operation complete in the counter. (CAUTION: make sure no other instruments will block the Counter's Service Requestby setting its address as low as possible)

3)when you send the start command you can poll the SRQ status with the "Wait for SRQ.vi"  If no signal is present then the Wait fo SRQ will return with a timeout error. 

4)Clear the error since you know what caused it and send a clear command (*CLR) to the counter to return it to the idle state.  

Alternately, if the signal is present, the counter will raise SRQ when the measurement is complete and you can then fetch the reading from memory.

[SAW Tester]

Jeff,

Thanks for the quick reply!  Setting the VISA TMO is a great wok around.  I tried it out and had good results.

Thanks so much for your help

[JÞB]

SAW-

You're quite welcome!  I'm glad we were able to get your code working!