Calibrating The Pci-Dda08/12; Self-Calibrating; Calibration Configuration - Measurement Computing PCI-DDA08/12 User Manual

Calibrating the PCI-DDA08/12

Self-calibrating

The PCI-DDA08/12 is shipped fully-calibrated from the factory. Calibration coefficients are stored in
nonvolatile RAM. When using the Universal Library, the calibration factors are read from nonvolatile RAM
and are automatically written to the calibration DACs each time you select a different DAC range.
You can recalibrate with respect to the factory-measured voltage standards by selecting the "Calibrate" option
in InstaCal. InstaCal calibrates each channel at all six ranges. Each channel takes less than a minute to
calibrate.

Calibration configuration

The PCI-DDA08/12 provides self-calibration of the analog source and measure systems. This eliminates the
need for external equipment and user adjustments. The analog output circuits are calibrated for both gain and
offset. Gain calibration of the analog output is performed via DAC reference adjustments. Offset adjustments
for the analog output is made in the output buffer section.
PCI-DDA08/12 calibration circuitry is shown in Figure 5-1.
Gain Adjust
Serial
Coarse
Trim DACs
Fine
Precision
2.5 V
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PGA
12-bit Output DAC
AD7837B
Vout
Vref
Offset Adjust
Serial Coarse
Trim DACs
Fine
Programable Voltage source
16-bit Reference DAC
serial
MAX542
X4
Coarse
Figure 5-1. Calibration block diagram
5-1
Output Voltage
Output
8x1
Voltages
Precision
Comparator
+
Setpoint Voltage
3 mS Gate
Chapter 5
COMP
Counter
5
CLEAR