Chapter 5
Calibrating the Board
Introduction
You should calibrate the board (using the
Insta
Cal 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 (PGIA) 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 5-1
Figure 5-1. Analog Input Calibration - Basic Elements
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
5-1
