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6.0 Self-Calibration of the PCI-DAS1200
The PCI-DAS1200 is shipped fully-calibrated from the factory with cal coefficients stored in nvRAM. When using
Universal Library at run time, these calibration factors are loaded into system memory and are 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-DAS1200 provides self-calibration of the analog source and measurment 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 max DAC and output buffer offsets.
Gain calibration of the analog outputs are performed via DAC reference adjustments.
Figure 1 below is a block diagram of the analog front-end calibration system:
Figure 1
17
PGA
ADC
Cal
Ref
Trim Dac
Offset
Offset Adj
Digital Offset Pot
Variable Gain
Trim Dac
(Coarse)
(Fine)
7
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