Necessity of GPIB-RS232 Converter

[imperial07]

Hello,

This may be a silly question but I just want to be sure.

Say I have a PC running Win7 and LabView and an instrument is connected to it with both a GPIB cable and and RS232 in its serial port. Will I be able to use VISA functions to send and receive serial data to the instrument or would it be better to use an NI GPIB-RS232 Converter? In what situations would said converter be useful?

Thanks!

[Sam_Sharp]

I think the GPIB converter is useful if you have multiple multiple instruments - a GPIB bus can have multiple devices connected to it. If you just have a single instrument, you can just stick with Serial.

That particular NI Device is useful for either converting a serial instrument to GPIB and vice-versa. The datasheet gives details of the different modes you can use it in: http://www.ni.com/pdf/products/us/2006_8248_rs232.pdf

[Dennis_Knutson]

Yes, you would use VISA with all three options. The fastest and more robust method is with GPIB. Personally, I see no point in the GPIB-RS232 converter. It's expensive and you are limited to the same RS232 baud rates that an inexpensive USB-RS232 converter gives you. I recommend FTDI based serial converters. You would probably need to modify any driver if you use the GPIB-RS232 as well.

The last time I saw and used the GPIB-RS232 converter was several years ago when I bought an instrument that the vendor said had a GPIB option. What it really had was the converter inside. Very disappointed by what I found.

[crossrulz]

I'm confused about what connections you have on your computer.  If you have a serial port and the instrument has a serial connection, just use that.  Preferrably, if you have a PCI(e)-GPIB card or a USB-GPIB, use that to connect to your instrument.

[imperial07]

The computer has a serial port and a PCI GPIB card, so it would be connected to the instrument with two cables - GPIB and serial. 

Thanks for the replies, it seems that the consensus is that the converter is uneccesary because I can just use the serial port on the computer. 

[Sam_Sharp]

The device is probably meant to work with either serial or GPIB - not both at the same time.

[crossrulz]

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@imperial07 wrote:

The computer has a serial port and a PCI GPIB card, so it would be connected to the instrument with two cables - GPIB and serial.

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NO.  You use GPIB OR serial.  In this case, use the GPIB.

[imperial07]

Hmm. I can only use one of them? The instrument I need to control needs to be sent commands with both GPIB and Serial. So would I need to use the converter then?

(I am building a LabVIEW program to replace the software that came with the instrument. Using GPIB and serial sniffers I can see that it uses both when it is running)

[Dennis_Knutson]

Your comment makes no sense. I've never heard of an instrument that requires both serial and GPIB connections. What is the make and model? What is the software you are monitoring?

[imperial07]

It is an old instrument: HL5500PC. However, now that I think about it, there are two parts that make up the instrument and the serial cable only connects to one of the parts. So technically it is two instruments. If I wanted to control both of these using one LabVIEW program would I use the converter?

Thank you guys for your patience with me.