User`s manual

6.0 SELF-CALIBRATION
The PCI-DAS1602/12 is shipped fully-calibrated from the factory with calibration coefficients stored in
nvRAM. At run time, these calibration factors can be loaded into system memory and can be automatically
retrieved each time a different DAC/ADC range is specified. The user has the option to recalibrate with
respect to the factory-measured voltage standards at any time by simply selecting the “Calibrate” option in
InstaCal. Full calibration typically requires less than two minutes and requires no user intervention.
6.1 CALIBRATION CONFIGURATION
The PCI-DAS1602/12 provides self-calibration of the analog source and measurement systems thereby
eliminating the need for external equipment and user adjustments. All adjustments are made via 8-bit
calibration DACs or 7-bit digital “potentiometers” referenced to an on-board factory calibrated standard.
Calibration factors are stored on the serial nvRAM.
A variety of methods are used to calibrate the different elements on the board. The analog front-end has
several “knobs” to turn. Offset calibration is performed in the instrumentation amplifier gain stage. Front-
end gain adjustment is performed via a variable attenuator/gain stage.
The analog output circuits are calibrated for both gain and offset. Offset adjustments for the analog output
are made in the output buffer section. The tuning range of this adjustment allows for maximum DAC and
output buffer offsets. Gain calibration of the analog outputs are performed via DAC reference
adjustments.
Figure 6-1 below is a block diagram of the analog front-end calibration system:
Analog-In
ADC
Cal
Ref
Trim Dac
Offset
RefOffset Adj
Offset Adj Uni/Bip
Digital Gain Pot
Digital Offset Pot
Figure 6-1. Block Diagram - Analog Front-end Calibration System
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