Read VISA signal on function generator

[Sim1]

Hi all,

I´m using labview (VISA I/O) to remote control a TGP3122 function generator. I set the wave parameter (kind of wave, frequency, amplitude ecc), turn on the wave, and then I want to read the voltage value, but I cannot find the command to do that.

In other words, when the function generator is working, I just want to know the voltage in that moment. How can I do? My idea was to use VISA write to ask the instrument for the value, and then VISA read, but as I said, there is not a command apparently.

Here is a link with the instrument manual, with all the remote commands: http://resources.aimtti.com/manuals/TGP3100_Series_Instruction_Manual-Iss2.pdf

Thank you for your help!

[RTSLVU]

That manual says the command "AMPL x " sets the amplitude to x Volts peak to peak

Try sending a AMPL? and see if it returns the AMPL setting.

[billko]

Are you actually looking for the value of the setting or the value of the data?

[RTSLVU · Accepted solution]

bilko brings up a good question... My suggestion will only tell you what the last amplitude setting was set to, not what the actual output  measurement is.

But an instrument needs to have a measurement subsystem to take measurements, most function generators lack this. 

If the instrument in question actually has a measurement subsystem then a query could look something like this:

MEAS:AMPL

But a quick scan of the manual I see no mention of a measurement subsystem or of any commands for determining the instrument's current settings. 

[Sim1]

infact I´m afraid there is no measurement subsystem. Now I´m not sure about what can I do. I can simulate the wave with some digital channel (with parameters equal to the instrument), but it will not to be the "real" value.

[RTSLVU]

Maybe with a little more information we can come up with an alternative or something. As it stands now you are going to need an external measurement device to measure the output of the function generator.

I guess my first question is: Why? 

I understand if you are attempting to automate a test procedure, and the procedure says to set the function generator to X freq at Y p-p that you need to verify that. 

Have you thought about calibrating the instrument so when you send the command to set its output to 2 Volts p-p it actually sets its output to 2 volts p-p? This can be a simple "in house" calibration using another calibrated measuring device and compare the voltages set to the actual volts output and working the "calibration factor" into your program.

[Minions]

We have some older stand that work on a calibration cycle where every few months, the stands are taken off-line and all of its outputs are verified and tweaked back into centered values.  Our newer systems monitor every signal to verify they meet requirements on an on-going basis.  The system will let us know when a value does not meet the windowed requirements.  Our measuring instruments are replaced on a scheduled basis with newly calibrated ones for limited stand down-time.

Another method that was touched on briefly is the use of Self-Test equipment/tools that run through a suite of tests that verify functional calibration against a calibrated measuring system.

[Sim1]

I need to know the voltage in "real time" because I want to measure the displacement of a piezoelectric cantilever, that respond on an applied voltage. I want to send also sine signals, with different frequencies. So I have to know the function generator output to know exactly the response of the piezoelectric material.

I think I can calibrate the instrument and then, simulate the signal with a virtual channel, or using a digital voltmeter.

[Minions]

Depending on your definition of "Real-time", you would require some type of digitizer or analog input to be able to monitor the signal for its reaction to a particular amplitude.

[ben64]

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Minions a écrit :

Depending on your definition of "Real-time", you would require some type of digitizer or analog input to be able to monitor the signal for its reaction to a particular amplitude.

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I totally agree with you. To add to your comment even if the generator had a measurement subsystem querying it would be far from real-time and the value read might be a bit different from the signal at the unit under test depending on your setup. Digitizer or analog input should also be used to measure the generator output, this way you would have synchronized measurements.

Ben64