User manual

Calibration

This chapter discusses the calibration procedures for the

NI 6034E/6035E/6036E device. If you are using the NI-DAQ device

driver, that software includes calibration functions for performing all of

the steps in the calibration process.

Calibration refers to the process of minimizing measurement and output

voltage errors by making small circuit adjustments. On the

NI 6034E/6035E/6036E device, these adjustments take the form of writing

values to onboard calibration DACs (CalDACs).

Some form of device calibration is required for all but the most forgiving

applications. If you do not calibrate your device, your signals and

measurements could have very large offset, gain, and linearity errors.

Three levels of calibration are available to you and described in this chapter.

The first level is the fastest, easiest, and least accurate, whereas the last

level is the slowest, most difficult, and most accurate.

Loading Calibration Constants

The NI 6034E/6035E/6036E device is factory calibrated before shipment

at approximately 25 °C to the levels indicated in Appendix A,

Specifications. The associated calibration constants—the values that were

written to the CalDACs to achieve calibration in the factory—are stored in

the onboard nonvolatile memory (EEPROM). Because the CalDACs have

no memory capability, they do not retain calibration information when the

device is unpowered. Loading calibration constants refers to the process of

loading the CalDACs with the values stored in the EEPROM. NI-DAQ

determines when loading calibration constants is necessary and does it

automatically. If you are not using NI-DAQ, you must load these values

yourself.

In the EEPROM, there is a user-modifiable calibration area in addition

to the permanent factory calibration area. The user-modifiable calibration

area allows you to load the CalDACs with values either from the original

factory calibration or from a calibration that you subsequently performed.

UM.book Page 1 Monday, May 14, 2001 10:32 AM