Agilent 34972A w/ RTD reading temp out of bounds.

[RansomErb]

Brief issue background, I inherited responsibility of a test setup. The engineer who built it and set it up no longer works for my company. We were using an Agilent 34970 to collect data from RTDs, and have moved on to using an Agilent 34972 to collect data. On the 34970 all values read on our RTDs were as expected. The Labview code I'm using should theoretically work for the 34972s as well, but for some reason all my RTD measurements are out of bounds now (9e37 C).

Here is where it gets odder. The RTDs are all PT1000, so the reference resistance is 1k Ohms, but if i set the ref. resistance to around 55.5 Ohms my readings are almost in line with that I would expect from the system... but I know that this setup is incorrect, because the reference resistance should be 1k Ohms.

I am a novice at Labview, and this is my first time working with the Agilent systems or RTDs, so I really have no idea whats going on here.

Going back to using the Agilent 34970 is not an option for me.

[cstorey]

If you could post a code snippet that show how you set and measure the RTDs, then there might be some help.

Otherwise read the manuals for both 34970 and 34972 to determine the subtle differences that are causing the problem.  I suspect the scales in the current source are different and this is causing your issue...but I can only guess without the code.

Craig

[RTSLVU]

That is confusing to say the least as the only difference between the 34970A and the 34972A  is the 34970A had RS-232 and GPIB while the 34972A has LXI (Ethernet) and USB communications options.

The underlying LabVIEW code has not changed except for I think the Initialize VI that now has options for the other communication options 

But the all the configuration and measurement VI's are identical for the 34970A and 34972A and in our lab we swap these out all the time and I never had to change a LabVIEW program when swapping a 34970A for a 34972A or vice-versa 

[RansomErb]

Relevant code is pictured here

[RansomErb]

I personally want to believe its a driver issue, but when I put apply scalings and whatnot, the Agilent unit is reading the same values as Labview, so it can't be a driver issue, can it?

It can't be an issue with the RTDs themselves, because I can change them out for a new set and get the exact results again.

[RTSLVU]

OMG... I shudder to think what the rest of that block diagram looks like. 

But being the glutton for punishment I am I will ask you to please post your code.

I don't have any RTD's handy but I do happen to have a 34972A attached to my workstation as I am typing this and can run your code.

---

@RansomErb

[RansomErb]

I'm really sorry to do this to you. Disclaimer, I showed you the best of the code. What I'm linking is a bare-bones version of the code, trust me its way worse.

[RTSLVU]

Why all the Timed Sequence Structures? 

That code is just wrong on so many levels that it would take longer for me to figure out what is wrong so you can fix it than it would to start over from scratch.

I am sorry but I must bow out of this one.

But I will give you a word of advice "State Machine", learn them, live them, and you will love them.

[RansomErb]

Well if it sets your mind to ease at all, I just used the BenchLink Data Logger to test the system, and it got the same results as the Labview program, so it seems as though the Agilent 34972 itself is the issue.

[RTSLVU]

Hmmm... well I have to say I have never worked with RTD's and this instrument, but even though I cannot imagine how a 34970 and 34972 could be different? 

Are you using the same 34901A MUX module in the 34972A as you had in the 34970A?

If you have that program struipped down to just initializing and reading the 34972A I will take a look at it and see if I notice anything.