two computers controlling one instrument

[bmihura]

I'd like to have two computers controlling one instrument.

Now I have one computer controlling the instrument via networked VISA connection. But it's an instrument with two modules that plug into one chassis, so it would be nice to dedicate each computer to its own module.

[RavensFan]

Can you provide details with your question such as what this instrument is?

I don't think you really have a LabVIEW question here, but a question about how your particular instrument functions.

[bmihura]

It's a Chroma 63000 series electonic load. But it behaves about the same as any other instrument from LabVIEW's point of view; send it a command, and it does its thing.

I've just never tried to make two computers contol one instrument.

[RavensFan]

But where does the "each module gets its own computer" fit in?

Theoretically, you could use a serial port Y adapter to connect to two different computers.  I don't know if it will actually work.  You'd have to deal with a problem of each computer not trying to send a message to the one device at the same time, otherwise the message would get garbled.  You'd have to come up with a means of detecting this has happened and be able to resend a message.  You'd also have to deal with any response from the device being sent to both computers, and each computer figuring out how to ignore a message that wasn't intended for it.

You might have a better chance to get this to work electrically if you converted all RS-232 signals to RS-485 or RS-422 which are intended for multi-drop installations.

[Omar_II]

I agree this is more a question for Chroma than for LabVIEW

I have some Chroma power supplies (but we use GPIB). The software that came with it had a remote panel for debuging. Do you have something simlar for Ethernet and have you tried to talk to it via the network from two computers? If you can do that then you should be able to do the same with LabVIEW

How do you address the individual modules over Ethernet?

Is one computer only going to control one set of modules and the other computer only going to control another set of modules.

Can Chroma accept commands over Ethernet network from more than one computer IP address.

Maybe Chroma does not care and will accept any command over the Ethernet network regardless what computer it comes from.

If not you may have to set one of the computer as the controller with some type of service accepting and relaying commands to the Chroma from both programs, One program local and the other on the 2nd computer sending request to the 1st via Ethernet.

[bmihura]

I can point each command to a specific module, like this: "chan 1;sour volt 80", which says set module (channel) 1 to 80 volts. Same idea with module 2.

My same question would apply if I had an instrument without multiple modules; computer 1 would get the instrument for a certain time range, then computer 2 would get the instrument for another time range.

Ethernet or USB would be OK as this instrument doesn't talk serial or GPIB.

[Dennis_Knutson]

If you don't do some sort of resource locking, you are almost certain to get a query interrupted error. There is a shipping example of this. I don't have a computer with me to look it up.