Measurement Computing PCI-DAS64/M2/16 - Manual (Page 23)

PCI-DAS64/M2/16 User's Guide Calibrating the PCI-DAS64/M2/16
Table 5-1. Recommended A/D calibration frequencies
Calibration Frequency (kHz) Min Sampling Frequency (kHz) Max Sampling Frequency (kHz)
2 0.01 6
15 6
30
50 30 70
100 70
200
300 200 400
650 400 1000
1250 1000 1500
1850 1500 2000
For best results, calibrate the board immediately prior to making your measurements. The high-resolution
analog components on the board are somewhat sensitive to temperature and this pre-measurement calibration
helps assure your board operates at the same temperature at which it was calibrated.
Calibration theory
Offset calibration for the analog front end is performed via adjustments of the ADC itself. Front-end gain
adjustment is performed only via the ADC reference. This strategy was chosen since the gain tolerance of the
in-amp circuit is quite good and there is adequate gain tuning range using only the ADC.
A block diagram of the analog front-end calibration system is shown in . Figure 5-2
Figure 5-2. Analog front-end calibration system
Analog In
ADC
Trim DAC
Coarse
Trim DAC
Fine
Trim DAC
Coarse
Trim DAC
Fine
MUX Gain
Adjust
Offset
Adjust
Calibration
Reference
5-2