LabVIEW
cRIO is not reading my transducer correctly
I've got a cRIO-9074 with an NI 9208 analog input module, running LV2019. I've also got a current transducer thats from phoenix contact, MCR-SL-CUC-600-I. It is a 3-wire 4-20mA output sensor. Datasheet below
https://www.alliedelec.com/m/d/d81db82a833161f3f4da08cce9dbf62e.pdf4
I've been trying to figure out why the heck labview is displaying values lower than what the actual current is. For example, at 7A, labview is displaying 3.3A. At 30A, labview is displaying 26A or so.
I've got it scaled in the analog inputs properties, 0-600A / 4-20mA.
And I have just a basic while loop with the AI0 shared variable wired to an indicator.
What I've noticed now is, after hooking up a Fluke 773 mA clamp meter (love this thing), my transducer is outputting about 4.16 mA, which is close to what it should be which is 4.186 mA.
But my cRIO is reading in 4.09mA!! This is what is displayed when I remove the scaling and just look at the raw value. Why on earth would I be able to measure 4.16mA on the wire that's going into the input, but the actual input is reading less??
Hi David,
@David99999 wrote:
For example, at 7A, labview is displaying 3.3A.
I've got it scaled in the analog inputs properties, 0-600A / 4-20mA.
after hooking up a Fluke 773 mA clamp meter (love this thing), my transducer is outputting about 4.16 mA, which is close to what it should be which is 4.186 mA.
But my cRIO is reading in 4.09mA!!
Simple calculations:
7A gives a sensor output of 7A/600A*16mA+4mA = 4.187mA, which is your expected value.
Reading 4.09mA instead gives a scaled value of (4.09mA-4mA)/16mA*600A = 3.375A, which is what the indicator is showing.
So all your values seem to fit, the scaling itself seems to work as expected!
(What's the accuracy of the clamp ammeter? What's the accuracy of the current source (aka current transducer), and what is the accuracy of the NI9208 module?)
@David99999 wrote:
At 30A, labview is displaying 26A or so.
I guess the same math applies to the readings as above…
Mind to share your VI? Can you show an image of the actual hardware wiring?
How fast are you trying to sample? The 9208 uses a delta sigma converter which has frequency limits compared to "normal" ADC's. Also, have you tried the high resolution mode? You could be seeing some 60 Hz interference.
