Measurement Computing DaqScan 2000 Series - Manual (Page 59)

Daqscan/2000 Series 948695 Calibration 9-1
Calibration 9
Overview …… 9-1
Using DaqCal.exe …… 9-1
Overview
Daqscan/2000 Series devices are digitally calibrated at the factory. The digital method
involves storing a correction factor on the circuit board for each range at the time of
calibration. Whenever a particular range is selected, the appropriate calibration constant is
automatically applied to a compensating DAC, thereby calibrating the specific range. The
result is that readings generated by the A/D are already calibrated, and do not require
additional processing.
This is significantly better than the calibration method in which readings are adjusted in
software after they are transferred to the host PC. That method reduces the dynamic range of
the A/D, and can adversely affect the speed at which the PC obtains a calibrated reading.
Daqscan/2000 Series devices include a user-cal mode, whereby the user can adjust the
calibration of the unit’s board, without destroying the supplied factory calibration. This is
accomplished with two distinct calibration tables in the unit’s on-board EPROM, one which
contains the factory calibration factors, and the other which is available for user calibration.
Using DaqCal.exe
When calibration adjustments are needed they should be completed in the following order:
1.
2.
3.
4.
5.
6.
7.
8. PGA Input and Output Offset
Sample/Hold Offset
A/D Offset and Gain
VDC Voltage Reference
DAC0 Full-Scale 1
DAC1 Full-Scale 1
DAC2 Full-Scale 1
DAC3 Full-Scale 1
1 DAC Full-Scale only applies to Daqscan/2001 and DaqScan/2004.
A Windows-based program, DaqCal.exe, is used to calibrate Daq systems, including analog
expansion cards. DaqCal.exe is used in conjunction with:
• a 4.5 digit, digital multi-meter
• an adjustable voltage calibrator
• an ambient temperature meter
To use the calibration program:
1. Launch DaqCal.
Note: DaqCal is installed automatically from your data acquisition CD as a part
of product support. This takes place during software installation. DaqCal’s
default location is the IOtech DaqX Software folder, in the Programs
group.
2. When DaqCal opens you will be prompted to select your device from a list. After
doing so, simply follow the illustrated on-screen instructions.