ADLINK PCI-9527 - Manual (Page 52)

40 Calibration
PCI-9527 ADLINK Technology Inc.
User’s Manual Copyright 2010
4.2 Auto-Calibration
Because errors in measurement and outputs will vary with time
and temperature, it is recommended to re-calibration when the
card is installed in the user’s environment. The auto-calibration
can measure and minimize errors without external signal connec-
tions, reference voltages, or measurement devices.
The PCI-9527 has an on-board calibration reference to ensure the
accuracy of auto-calibration. The reference voltage is measured
on the production line and recorded in the on-board EEPROM.
Before begining the auto-calibration procedure, it is recommended
to warm up the PCI-9527 for at least 20 minutes. Please remove
cables before an auto-calibration procedure is initiated.
4.3 Offset Error Compensation During AI Sampling
Rate Change
To provide better measurement results, PCI-9527 has an internal
offset error compensation mechanism whenever user changes the
AI sampling rate. Following table shows the compensation time
required when setting different sampling rate. For example, when
changing the sampling rate from 432 KS/s to 2 KS/s, 6.2 sec is
required for offset compensation. Next time when the sampling
rate is set between 2 KS/s and 53.999 KS/s, it is not necessary to
have 6.2 sec for the offset compensation. Only the sampling rate
set to different ranges will cause a compensation time.
Note that it is not necessary to add delay in you application. The
PCI-9527 driver will automatically add the compensation time.
Sampling Rate 2 KS/s -
53.999 KS/s 54 KS/s -
107.999 KS/s 108 K/s -
215.999 KS/s 216 KS/s -
432 KS/s
Offset Compen-
sation Time 6.2 sec 2.6 sec 1.3 sec 0.65 sec
Table 4-1: Offset Compensation Time Required for Different Sampling
Rates