Measurement Specialties PCI-DAS64/M2/16 Calibration theory, Analog front-end calibration system

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.

	Analog In
Calibration		ADC
	MUX	Offset	Gain
Reference
		Adjust	Adjust

Trim DAC

Coarse

Trim DAC

Fine

Trim DAC

Coarse

Trim DAC

Fine

Figure 5-2. Analog front-end calibration system

5-2