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Trouble communicating with voltage source (Data Precision 8200) with VISA


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Hello,

I am trying to control a voltage source (DP 8200) through VISA in LabVIEW. I have connected the instrument to my system using a GPIB connector. When I scan in MAX, the instrument shows up and switches to remote mode, but does not respond to the IDN query. I'm assuming that the machine does not have read abilities here. The commands to the instrument are very elementary. For example "V2+500000" means voltage mode - 2nd range of 100V - positive polarity - set to 50.0000 V'. However, I cannot get the instrument to respond. I have tried writing a simple VISA program attached here (that gave no errors) and I have tried using the NI 488.2 Communicator.  I have tried to remove zeros, add them, add quotation marks, add \r, add \n, add \r\n, lowercase v, with a decimal, without a decimal.... I have changed the EOS configuration settings. Any other suggestions?

 

Thanks!

VISA_Code.jpg

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Do you get a response to IDN query via MAX VISA Test panel? If not, check your hardware.

For the VISA write, make sure your string is set to  '\' Codes display, and add a \n - line feed, not a literal \n.

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Hmmm, that's one old piece of hardware. I found a manual here: https://www.opweb.de/deutsch/firma/Data_Precision/herunterladen/Data_Precision--8200--service--ID8215.pdf and its covere page has a copyright of January, 1981.

Instruments from that time do not comply to IEEE 488.2 at all since that standard simply did not exist then. That only was released in 1987.

Accordingly GPIB instruments where using all kinds of weird GPIB settings, including instruments from the GPIB inventor HP itself.

You may have to actually go into NI-MAX and change settings for the instrument or even the GPIB controller itself, that listen to names like "enable readdressing" and other possible settings. This was way into the 90ies the main issue about connecting legacy GPIB instruments to a computer. The fact that the few available GPIB controller chips all had their quirks and bugs, that had to be worked around in the instrument firmware, did not make it more simple.

Edited by Rolf Kalbermatter
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6 hours ago, Gribo said:

Do you get a response to IDN query via MAX VISA Test panel? If not, check your hardware.

For the VISA write, make sure your string is set to  '\' Codes display, and add a \n - line feed, not a literal \n.

The instrument did not respond to an IDN query, but I believe its because it does not have read capabilities. The address is set to 20 and it reads it as such and switches to remotely when I scan for instruments. 

As for your second comment, I have configured the settings to add an EOS. Is that what you are referring to?

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6 hours ago, Rolf Kalbermatter said:

Hmmm, that's one old piece of hardware. I found a manual here: https://www.opweb.de/deutsch/firma/Data_Precision/herunterladen/Data_Precision--8200--service--ID8215.pdf and its covere page has a copyright of January, 1981.

Instruments from that time do not comply to IEEE 488.2 at all since that standard simply did not exist then. That only was released in 1987.

Accordingly GPIB instruments where using all kinds of weird GPIB settings, including instruments from the GPIB inventor HP itself.

You may have to actually go into NI-MAX and change settings for the instrument or even the GPIB controller itself, that listen to names like "enable readdressing" and other possible settings. This was way into the 90ies the main issue about connecting legacy GPIB instruments to a computer. The fact that the few available GPIB controller chips all had their quirks and bugs, that had to be worked around in the instrument firmware, did not make it more simple.

Thanks for the feedback. I found the manual here (http://www.ko4bb.com/manuals/128.146.189.114/DataPrecision_8200_6.5_Digit_Calibrator_Service_Manual.pdf) and there is a section on 488.2 commands. I think the specific machine I have is from 1987. 

I'll play around with the settings to see if that helps.

Edit to add: I went back and looked at the possible options to change under MAX and there's nothing. Its such a simple machine that I cannot change anything. The only option available was "VISA Alisa". Under device status, it said the device was working fine.

Edited by bw2432
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On 11/13/2020 at 8:14 PM, bw2432 said:

Thanks for the feedback. I found the manual here (http://www.ko4bb.com/manuals/128.146.189.114/DataPrecision_8200_6.5_Digit_Calibrator_Service_Manual.pdf) and there is a section on 488.2 commands. I think the specific machine I have is from 1987. 

I'll play around with the settings to see if that helps.

Edit to add: I went back and looked at the possible options to change under MAX and there's nothing. Its such a simple machine that I cannot change anything. The only option available was "VISA Alisa". Under device status, it said the device was working fine.

The manufacturing year is irrelevant. When that device was designed in 1981 or before, that’s the technology it uses. Your device may contain a new firmware which fixes a bug or two but certainly not with new improved functionality.

As to those settings they absolutely positively must exist in NI-Max. They are functionality of the NI-488.2 driver and have absolutely nothing to do with your specific device. Or are you using something else than a NI GPIB interface to connect to the device? This is what you should see for your GPIB controller in MAX:

GPIB.png.f615bb2bcd984225cc55abf6c158ccba.png

As you can see there are a number of settings that could be relevant. Considering the age of the device I would guess playing around with Bus Timing (make it slower as the old GPIB controller used in that device might not really be up to snuff with modern GPIB timing), and Assert REN when SC (assert remote enable hardware handshake) might actually have an influence.

There should be a similar section with options when you select your device instead in the device tree. But I couldn't find an image of that easily and I haven't used GPIB in several years so can't quickly get a screenshot from one of my machines.

As to the GPIB section in the manual there is absolutely nothing that resembles anything IEEE 488.2. They only mention IEEE488 and the little they have in there is absolutely not 488.2 compatible in any shape or form.  HP used to fill 10-20 pages and more about all the different GPIB capabilities and features of their devices and several 100 pages about the commands you could use! 😀

The GPIB standard may be technically several magnitudes less challenging than PCIe, to just name one, but you needed to know more about the different capabilities of the device and your controller to make it work. IEEE 488.2 was an attempt to define a common set of features a device and controller should use and also to define some basic commands and their syntax (such as *IDN?).

Edited by Rolf Kalbermatter
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On 11/14/2020 at 5:27 AM, Rolf Kalbermatter said:

The manufacturing year is irrelevant. When that device was designed in 1981 or before, that’s the technology it uses. Your device may contain a new firmware which fixes a bug or two but certainly not with new improved functionality.

As to those settings they absolutely positively must exist in NI-Max. They are functionality of the NI-488.2 driver and have absolutely nothing to do with your specific device. Or are you using something else than a NI GPIB interface to connect to the device? This is what you should see for your GPIB controller in MAX:

GPIB.png.f615bb2bcd984225cc55abf6c158ccba.png

As you can see there are a number of settings that could be relevant. Considering the age of the device I would guess playing around with Bus Timing (make it slower as the old GPIB controller used in that device might not really be up to snuff with modern GPIB timing), and Assert REN when SC (assert remote enable hardware handshake) might actually have an influence.

There should be a similar section with options when you select your device instead in the device tree. But I couldn't find an image of that easily and I haven't used GPIB in several years so can't quickly get a screenshot from one of my machines.

As to the GPIB section in the manual there is absolutely nothing that resembles anything IEEE 488.2. They only mention IEEE488 and the little they have in there is absolutely not 488.2 compatible in any shape or form.  HP used to fill 10-20 pages and more about all the different GPIB capabilities and features of their devices and several 100 pages about the commands you could use! 😀

The GPIB standard may be technically several magnitudes less challenging than PCIe, to just name one, but you needed to know more about the different capabilities of the device and your controller to make it work. IEEE 488.2 was an attempt to define a common set of features a device and controller should use and also to define some basic commands and their syntax (such as *IDN?).

I see now. I was referring to the device settings. Thanks for clarifying. I have changed the 2 settings you mentioned. I'm guessing since the commands in the manual are not IEEE 488.2 compatible then VISA functions are out of the question. How about GPIB functions in LabVIEW?

Once again, thanks for all the help and patience.

Brandi

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2 hours ago, bw2432 said:

I see now. I was referring to the device settings. Thanks for clarifying. I have changed the 2 settings you mentioned. I'm guessing since the commands in the manual are not IEEE 488.2 compatible then VISA functions are out of the question. How about GPIB functions in LabVIEW?

Once again, thanks for all the help and patience.

Brandi

VISA can access also IEEE488 devices. The relevant settings can almost all be accessed through VISA properties. 

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13 hours ago, Rolf Kalbermatter said:

VISA can access also IEEE488 devices. The relevant settings can almost all be accessed through VISA properties. 

Earlier you said "As to the GPIB section in the manual there is absolutely nothing that resembles anything IEEE 488.2. They only mention IEEE488 and the little they have in there is absolutely not 488.2 compatible in any shape or form." I misread this and thought maybe VISA couldn't access it. I tried the program I wrote earlier, the one in the attached picture, and it still does not work. Do you suggest just playing with the settings more? 

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40 minutes ago, bw2432 said:

Earlier you said "As to the GPIB section in the manual there is absolutely nothing that resembles anything IEEE 488.2. They only mention IEEE488 and the little they have in there is absolutely not 488.2 compatible in any shape or form." I misread this and thought maybe VISA couldn't access it. I tried the program I wrote earlier, the one in the attached picture, and it still does not work. Do you suggest just playing with the settings more? 

I was refering to the instrument manual. That one has absolutely nothing to do with VISA whatsoever. It has about two half pages of IEEE description and some very limited command description. Not very extensive in any form and flavor.

NI VISA on the other hand is very capable of also accessing IEEE488.1 devices, which is the name of the old style IEEE488 interface specification. Doing so is however not trivial as those low level settings can be obscure and not easy to understand without knowing how the GPIB bus works on signal level. And it is usually not necessary since all the modern devices simply work with IEEE 488.2 settings which are the default when you open a GPIB VISA session.

But reading through the entire thread again, I would say the first thing you should do is to make sure you send the correct string. For Voltage mode it seems it should contain 10 characters whereas for current mode it would need 8 characters. 

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On 11/16/2020 at 8:59 AM, Rolf Kalbermatter said:

I was refering to the instrument manual. That one has absolutely nothing to do with VISA whatsoever. It has about two half pages of IEEE description and some very limited command description. Not very extensive in any form and flavor.

NI VISA on the other hand is very capable of also accessing IEEE488.1 devices, which is the name of the old style IEEE488 interface specification. Doing so is however not trivial as those low level settings can be obscure and not easy to understand without knowing how the GPIB bus works on signal level. And it is usually not necessary since all the modern devices simply work with IEEE 488.2 settings which are the default when you open a GPIB VISA session.

But reading through the entire thread again, I would say the first thing you should do is to make sure you send the correct string. For Voltage mode it seems it should contain 10 characters whereas for current mode it would need 8 characters. 

Yes, I have included the zeros behind the command with decimal and without.  The command is so simple, yet not working for me. 

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16 hours ago, bw2432 said:

Yes, I have included the zeros behind the command with decimal and without.  The command is so simple, yet not working for me. 

I find the description of the command syntax in the manual anyhow highly ambigious and unclear. Usually GPIB devices from that time were supposed to state one long list of capabilities in the form of abbreviations. Those were pretty important before IEEE 488.2 was released, since the GPIB bus had many capabilities and most devices only supported a subset of them. IEEE 488.2 defined a minimum set of capabilities that a device had to support in order to claim 488.2 compatibility (in addition to basic command syntax and such) and after that this capability list got almost completely redundandent.

A GPIB complying device that does not support 488.2 is supposed to list these capabilities somewhere. Usually they were both mentioned in the manual as well as a sticker somewhere on the outside of the device. 

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5 hours ago, Rolf Kalbermatter said:

I find the description of the command syntax in the manual anyhow highly ambigious and unclear. Usually GPIB devices from that time were supposed to state one long list of capabilities in the form of abbreviations. Those were pretty important before IEEE 488.2 was released, since the GPIB bus had many capabilities and most devices only supported a subset of them. IEEE 488.2 defined a minimum set of capabilities that a device had to support in order to claim 488.2 compatibility (in addition to basic command syntax and such) and after that this capability list got almost completely redundandent.

A GPIB complying device that does not support 488.2 is supposed to list these capabilities somewhere. Usually they were both mentioned in the manual as well as a sticker somewhere on the outside of the device. 

I most definitely agree; the manual is lacking. I posted on another site and someone had success with keysight interactive IO. I'm in the process of downloading this with fingers crossed.

https://www.eevblog.com/forum/testgear/data-precision-8200-not-responding-to-gpib-commands-no-errors/msg3317788/#msg3317788

She reported that the 10 character command worked - no decimal and trailing zeros.

I'll look on the instrument to see if I see any commands, but I do not recall seeing any.

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