Simultaneous measurement of thermocouples and voltage signals (Agilent 34970A)

[HRI_Michael]

Hello,

I have a problem reading thermocouples and 0-10 V voltage signals simultaneously with an Agilent 34970A in LabView.

I used the Agilent components from the "HP34970A Advanced Scan" example. The VI and a screenshot are attached.

If I read out the thermocouples only, the VI works. Reading out the voltages alone also works. I can also read out resistance sensors without any problems.

The problem occurs as soon as I want to read thermocouples and voltage signals simultaneously (in one scan). The Agilent then gives an error tone. (Thermocouples and resistance sensors at the same time or voltage signals and resistance sensors at the same time are also no problem.)

I suppose the reason for this is that the thermocouples are in principle also a voltage measurement. If I use the BenchLink software, everything works simultaneously without any problems - so it is possible in terms of hardware. Is there a way to use the Agilent components in LabView so that thermocouples and voltage signals can be scanned simultaneously?

Best regards,

Michael

[Minions]

You do understand that the Agilent/Keysight 34970A is not performing these measurements simultaneously.  It controls the connection relays and sets the single internal DMM to the modes defined during the scan channel configuration.  A channel must be set up as only a single configuration (Temp, Voltage,...) in order for the system to operate properly.  It appears that you are using the same inputs and trying to define them differently.  If that is the case then that will not work.

[HRI_Michael]

Thank you for pointing that out. In fact, "simultaneously" is an inappropriate term. I meant that a thermocouple and an analog voltage signal are read out in one scan.

Each Chanel has only one configuration. E.g. 101 for a thermocouple and 304 for a voltage measurement.

[cstorey]

Are you sure that each channel you are using can be configured to make the measurements you want?  Not all cards are created equal.

So what error messages does the instrument give you?   The error messages will tell you what the problem is from the instruments perspective, then fix your code to please it.

Craig

[Minions]

In other words, what Craig is asking is what modules (3490_A) are you using in each slot?

100:

200:

300:

[HRI_Michael]

I'm using three 34901A cards (20 Ch Multiplexer). And the Error is independend of the card (the error occurs both when I connect the thermocouple to 101 and the voltage signal to 102, as well as the combination 101 + 201, 202 + 305 and any other).

The cards and used channels are defenetly able to read the signals, since the reading of "only thermocouple" or "only voltage signal" works correctly.

Unfortunately I did not get an error code. The LabView error-reading-component says "no error", but the Agilent divce shows the error symbol on its display and makes an error tone.

[cstorey]

The LabVIEW driver for the instrument has a few vi to query for errors.  Add those into your code as shown...I made it messy on purpose!  You'll want to add in an error query after every setting, possibly put them in case structures and use a Boolean "Debugging" setting to toggle ON/OFF.

With the error querrying ON use highlight execution to see what the instrument is telling you.  Chanses are there's one bad parameter that is causing the issue.

Craig

[HRI_Michael]

Hello cstorey,

thank you very much for your help and the attached VI and sorry for the late reply, I was on business trip.

The error message "-222" or "Data out of range" is displayed (see screenshot).

The Agilent manual therefore contains the following information:

"A data element (not violating the standard) outside the range defined by this instrument has been received. This error occurs when an integer-based command for which the parameter can be rounded exceeds the range of -65536 to +65536 or when a real-number-based command for which the parameter can be rounded exceeds the range of -9.9e37 to +9.9e37, for example.

This error occurs also when a numeric value other than a specified one is entered into a command in which the "port number" and "CalKit number" are specified as parameters and hence the parameters are not rounded. Such commands are, for example, CALC:FSIM:BAL:TOP:BBAL:PPOR, SENS:CORR:COLL:ACQ:OPEN, SENS:CORR:COLL:ECAL:SOLT3, SENS:CORR:COLL:CKIT:ORD:LOAD, etc."

However, I suspect the mentioned error rather as a "secondary effect", because the measuring ranges are determined automatically anyway (manual specification does not change anything) and the measurements work individually.

Kind regards,

Michael

[Minions]

Try inserting this Simple VISA snippet after you configure your channels.  Enter the following into the write buffer.

SCAN:ROUT?;

What is the response in the read buffer?

[HRI_Michael]

Thank you for your support. I'm affraid I did not get you right, where to put the snippet content in my VI.

Here is a Screenshot of my first try - which is not working even with thermocouples only...