Measurement Computing PCI-DAS6013 - Manual (Page 29)

29
Chapter 4
Calibrating the Board
Introduction
You should calibrate the board (using the InstaCal utility) after the board has fully warmed up. The
recommended warm-up time is 15 minutes. For best results, calibrate the board immediately before making
critical measurements. The high resolution analog components on the board are somewhat sensitive to
temperature. Pre-measurement calibration ensures that your board is operating at optimum calibration values.
Calibration theory
Analog inputs are calibrated for offset and gain. Offset calibration for the analog inputs is performed directly on
the input amplifier, with coarse and fine trim DACs acting on the amplifier.
For input gain calibration, a precision calibration reference is used with coarse and fine trim DACs acting on the
ADC (see Figure 28).
Trim DAC
Coarse
Trim DAC
Fine
Gain
Adjust
PGIA Analog In A/D
Trim DAC
Coarse
Trim DAC
Fine
Pre-Gain
Offset
Trim DAC
Coarse
Trim DAC
Fine
Post-Gain
Offset
Figure 28. Analog input calibration - basic elements