Hi so I'm trying to program this SR720 LCR meter via a USB/GPIB interface. I can communicate with the machine and it's almost doing what I want, but has this strange quirk, and I suspect I'm missing something basic. The manual can be found here.
It responds to common GPIB commands like *IDN? (identify the instrument) and *IFC (device clear), so I'll be using those. The one I want to use myself is xall?, which just requests the data currently measured.
The problem is that it seems like the machine always "lags" one command late. For example, if I query *IDN? with NI MAX, it returns what it should. However, if I then query xall?, it still returns the same thing as *IDN?, until I do xall? again, and then it returns what it should:
-> *IDN?<- StanfordResearchSystems,SR720,08087,1.03
-> xall?<- StanfordResearchSystems,SR720,08087,1.03
-> xall?<- G1C7.0992E-08,G1R3.1788E02,99
Likewise if you go in the other direction:
-> xall?<- G1C7.0992E-08,G1R3.1788E02,99
-> *IDN?<- G1C7.0992E-08,G1R3.1790E02,99
-> *IDN?<- StanfordResearchSystems,SR720,08087,1.03
As you can see, it's "lagging" one command.
The manual says:
Similarly, the SR715/720 has a 256 character
output buffer to store output until the host
computer is ready to receive it. If the output buffer
fills up it is cleared and an error reported. The
GPIB output buffer may be cleared by using the
Device Clear universal command.
So I thought I'd try the device clear command (*IFC) before entering a new command, but it doesn't seem to work:
-> *IDN?<- StanfordResearchSystems,SR720,08087,1.03
-> *IFC
-> xall?<- StanfordResearchSystems,SR720,08087,1.03
-> xall?<- G1C7.0997E-08,G1R3.1761E02,99
Does anyone have any idea what might be going on? The manual says to use line feed as the terminating character, so I am, but it doesn't seem to matter.
