6.0 SELF-CALIBRATION OF THE PCI-DAS1000
The PCI-DAS1000 is shipped fully-calibrated from the factory with cal coefficients stored in nvRAM. 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.
6.1CALIBRATION CONFIGURATION
6.1.1Analog Inputs
The PCI-DAS1000 provides self-calibration of the analog source and measure systems thereby eliminating the need for external equipment and user adjustments. All adjustments are made via 8-bit calibration DACs or 7-bit digital potentiome- ters 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:
Cal
RefPGA
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Variable Gain
ADC
7
Digital Offset Pot
