SCXI-1001 with SCXI-1100 cards reading inconsistent between modules

[John at HHT]

There is +/- 10 deg. C from module to module, but only +/- .5 deg. C within the module. The individual board cjc temps are within +/- .5 deg. C of each other. What would cause this type of fluctuation?

System overview
SCXI-1001 with
12 SCXI-1100 (10 KHz Filter) and SCXI-1303 blocks
PCI-6034E Card
Type K TC
LabView 7.1
MAX 3.1.1

New to labView so any help is appreciated,

John

[JaredA]

Some of the uncertainty in measurements may simply be inherent to the hardware that you are using. You may want to consider pulling up the manuals for the termianl blocks and/or the modules to see the uncertainty that you can expect in the CJC measurements. +/- 0.5 C does not sound out of the ordinary.

What does sound strange is a +/- 10 degree C between modules - this is no small difference. Are you using an example program to take your measurements, or have you simply setup some DAQ Assistants on a block diagram to perform your readings? What is the level you are expecting to see, and what are the actual levels you are seeing across the different channels in your system?

To get such an enormous amount of uncertainty in temperature across modules is either going to come down to impromper hardware setup and configuration, software configuration, or a poorly calibrated system.

Jared A

[John at HHT]

I have tried using an example program and creating one with the DAQ assistant. All of the DAQmx example show the same intermodule inconsistencies, but if I use the Traditional DAQ SCXI-1100 example and measure the modules one at a time the intermodule difference is +/- 1 Deg. C which is acceptable and expected.

One thing I noticed is if you acquire the data in 2D DBL with DAQmx there are random blank (0) readings. I have it set to read 50 samples per ch at a rate of 512 S/s with a 10s time out and a filter setting is 10kHz. Is this a sign of hardware failure? Is the interchange delay slower in the Tradition DAQ default vs MAX setting it at a minimum time? Is the interchange delay settable in LabView?

Thanks,
John

[George M.]

HI,

Could you post your code to see how you have programmed this. Also, which DAQmx example were you using that didn't work. I look forward to your reply.

George

[John at HHT]

Hi,

I have attached the traditional DAQ & DAQmx examples. Also there is a program that I created to read the CJC and temp. Any suggestions are greatly appreciated.

Thanks,
John

[George M.]

Hi,

So, when you run the DAQmx example, w/o changing any of the rate specifications, do you see this fluctuation in data. Also, are you seeing this temperature differences in MAX. If you change the thermocouples from two modules, will you show the same data based on the thermocouple or the module. That is, I am wondering if this is an issue with the thermocouples or the hw. So, first open up MAX and see if you are seeing the same readings. Then, change out the thermos from one module and place them in another. Then, check to see if the temp is the same as it was, or see if it changed to the temp when the thermos were in the other module. I hope this helps, and let me know what happens. Have a Great Weekend!

George

[MrDoc]

I am having a similar problem. 

SCXI-1000 with SCXI1100 and SCXI1303 reading thermocouples on all 4 1303's.

This setup is working fine running with rev 5.1 Labview.

I am trying to convert to run this with Labview 8.5 on a different PC.

Both setups use the same SCXI-1000 setup, the only difference is from the cable off this to the two PCs.

I have the program reading the thermocouples with the new PC, but there are 3-4 different temp levels when I just try to read ambient levels.

The levels are from 0.5°C above ambient to 7°C above

No heat or cooling running just reading ambient.  The old labview/PC reads ALL temps the same.

I switch to the new system and I get different levels.

I am reading the cjtemp and adding this to the readings.

Both systems give CJC temp as the same level.