Can I Perform an External Calibration for my DAQ Device in LabVIEW?

Updated Nov 8, 2018

Reported In

Driver

  • NI-DAQmx

Issue Details

My measurement hardware needs an external calibration. Is there a way to perform this in LabVIEW?

Solution

External calibration is the most involved calibration procedure and it requires a highly precise voltage source. When an external calibration is performed, the EEPROM calibration constants are physically overwritten and new ones are applied. This procedure requires using a high-precision voltage source to verify and adjust calibration constants. Because the external calibration procedure changes all EEPROM constants, it invalidates the original calibration certificate. If an external calibration is done with a NIST-certified voltage source, a new NIST traceability certificate can be issued. External calibration is typically performed by a metrology lab, but can be performed in LabVIEW. 

The Calibration Procedure Manual  article provides specific guidelines for performing an external calibration for specific measurement hardware. The calibration procedure manuals do not discuss programming techniques or compiler configuration. 

Additionally, NI-DAQmx includes high-level function calls to simplify the task of writing software to calibrate devices. DAQmx Calibration VIs and Functions are available in LabVIEW to perform both internal and external calibrations. For information on these VIs, refer to the Help Manual information: DAQmx Manual: DAQmx Calibration VIs and Functions.

Figure 1 - DAQmx Calibration Functions Palette in LabVIEW 
 
As the calibration procedure manuals describe, the DAQmx Intialize External Calibration VI, DAQmx Adjust Y-Series Calibration (where Y is series of the device), and DAQmx Close External Calibration VI are used to perform the calibration using LabVIEW. More information about these VIs can be found in DAQmx Help and LabVIEW Help. 
 

Additional Information

National Instruments offers several Calibration Services

Depending on the hardware and accuracy requirements of your application, National Instruments recommends an external calibration every 1 to 2 years. The recommended Calibration Interval can be found on the device’s specification sheet. External calibrations are important to maintaining device accuracy. The performance of any given analog-to-digital converter can vary according to temperature, input voltage, time, and other factors.

National Instruments also recommends that you self-calibrate (i.e. internal calibration) most devices after installation and whenever the ambient temperature changes. This information can also be found in the hardware’s User Manual. Detailed information about performing a self-calibration is also on the Manual Calibration Procedure page.

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