National Instruments 320174B-01 用户手册

                                                                                                                     

This chapter discusses the calibration procedures for the Lab-NB analog input and analog output
circuitry.

The Lab-NB is calibrated at the factory before shipment.  To maintain the 12-bit accuracy of the
Lab-NB analog input and analog output circuitry, recalibration at six-month intervals is
recommended.  Recalibration is also recommended whenever the input or output configuration is
changed.

Factory calibration is performed with the Lab-NB in its default factory configuration:

• ±5 V analog input range (bipolar)

• ±5 V analog output range (bipolar)

For best measurement results, the Lab-NB needs to be calibrated so that its measurement
accuracy is within ±0.012% of its input range (±0.5 LSB).  According to standard practice, the
equipment used to calibrate the Lab-NB should be 10 times as accurate, that is, have ±0.001%
rated accuracy.  Practically speaking, calibration equipment with four times the accuracy of the
item under calibration is generally considered acceptable.  Four times the accuracy of the
Lab-NB is 0.003%.

You need the following equipment to calibrate the Lab-NB board:

•

For analog input calibration, you need a precision variable DC voltage source (usually a
calibrator) with these features:

-

Accuracy

±0.001% standard
±0.003% sufficient

-

Range

Greater than ±10 V

-

Resolution

100 µV in ±10 V range (5

1

/

2

 digits)

•

For analog output calibration, you need a voltmeter with these features:

-

Accuracy

±0.001% standard
±0.003% sufficient

-

Range

Greater than ±10 V

-

Resolution

100 µV in ±10 V range (5

1

/

2

 digits)