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NI 9225 in house calibration?

Hey community,

 

I have found this document about the NI 9225. The document describes how to check if the NI 9225 is still within the calibrated gain and offset errors. If not then send back to NI for recal. I understand this part. But what if - after a year - the module is still accurate enough?? Can I change calibration date in the EEPROM (we have a routine which checks the cal date for every unit once the station is turned on).

 

This modules doesnt support the self calibration button in MAX, or the self cal VI in daqmx. (we use the NI 9178 cDAQ chassis)

 

please advice!

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This is not recommended!

 

Updating the calibration date without properly doing a calibration does not guarantee that your device will remain calibrated for the one-year period. While you may still be reading a proper value now, doing an external calibration will adjust your device to a tighter tolerance that will be valid for the next year. The 9225 doesn't support self calibration, but that is separate and independent from an external calibration. 

Nathan Murphy
Certified LabVIEW Architect
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Thanks for your answer. We have the resources to perform a calibration in every 3 months if neccessary. How can we update the cal dates in the eeprom?

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Great! In that case, simply open and close a calibration session from within a VI. You can find these functions in the DAQmx Calibration functions palette. When you close the calibration session, make sure you commit the changes. 

Nathan Murphy
Certified LabVIEW Architect
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Now with more snippet!

 

calibration.png

Nathan Murphy
Certified LabVIEW Architect
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Kudos. Works like a charm. Now is there a way for us to perform a proper calibration including the update of the cal constants?

 

thanks!

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Message 6 of 17
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I think this is what you are looking for: 

 

calibration.png

 

Note that you should still be following the calibration procedure and using the recommended test points and other values. Other than that, the process is fairly straight-forward. 

Nathan Murphy
Certified LabVIEW Architect
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For more information on the VIs used, you can view our online help docs here.

Nathan Murphy
Certified LabVIEW Architect
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Alright... I understand that the temperature comes from an external measurement. But where is the reference point coming from? I checked the VI you have linked it provided me an array with 51 elements for an NI 9229 (this is the module I have access at this very moment)

 

I am trying to make a guess here... does you snippet means that I should set all the 51 voltages on the calibrator and run this snippet 51 times for each channels? 

 

I am not sure how is this relates back to the document I have linked.

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I don't understand what you mean when you mention an array. The subVI used in step three is the DAQmx Adjust C Series Calibration. It is a polymorphic VI that can change to work for whichever c series module you are trying to calibrate. When I change my VI isntance to 9229, it still will only accept 1 value on the reference value input. Try deleting and dropping down the VI from the functions palette to see if that fixes it. The VI is located in the following palette:

Measurement I/O » NI-DAQmx » DAQmx Advanced » Calibration » C Series Calibration

 

The reference point is an external precision voltage that you supply into the channel that you are calibrating. This should be a known voltage. Wire this voltage value into the VI in step 3. 

 

The document you have linked is the calibration procedure, which mostly discusses how to check if the device needs calibration. However it also has some test points that would be good to test. 

 

If this dow not work, please provide a screenshot of the code.

Nathan Murphy
Certified LabVIEW Architect
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