Filter
Top Products
©
National Instruments Corporation 5-1 PCI-4451/4452 User Manual
5
Calibration
This chapter discusses the calibration procedures for your PCI-4451/4452
device. Your PCI-4451/4452 is shipped with a calibration certificate. The
traceability information is stored in National Instruments corporate
databases and is not actually shown on your certificate. The certificate
contains a unique tracking number linking your device to the database. You
can get a detailed calibration report from National Instruments for an
additional charge.
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
PCI-4451/4452 devices, 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
and gain errors. The four levels of calibration available are 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
Your PCI-4451/4452 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 software
determines when this is necessary and does it automatically.
The EEPROM contains a user-modifiable calibration area in addition to
the permanent factory calibration area. This means that you can load the
CalDACs with values either from the original factory calibration or from a
calibration that you subsequently performed. This method of calibration is
User.book Page 1 Tuesday, April 14, 1998 10:20 AM