CONTREX CX-1200 - Manual (Page 92)

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Calibrating and Scaling AI1 Together
In some applications you may know the voltage (or current) to EU representation, but you have no idea the
voltage produced by the sensor at either end point. You can ‘calibrate’ the signal directly in terms of EU by
setting the calibration references the same as the scaling references, i.e. set AI1 RA (CP-281) equal to
AnlgCal Ref A (MP-168) for this signal and set AI1 RB (CP-283) equal to Cal Ref B (MP-169) for this
signal. These two points should be discretely different from each other and should be reasonable estimates
for the actual voltage or current range. You would then set the EU@ AI1 RA (CP-282) and EU@ AI1 RB
(CP-284) to the sensor’s operating points used during the calibration process for points A and B respectively.
1. Connect the sensor to the AI1 voltage (or current) pins. Connect pins 3 and 4 together if
using current mode.
2. Set AI1 Mode (CP-280) to “Volts” (1) or “Current” (2).
3. Set Analog Cal Sel (CP-461) to “AI1” (1) to Select AI1 for calibration.
4. Set Analog Cal Ref (CP-462) to “A” (1) to select point A.
NOTE: The old calibration data will be overwritten.
5. Set Analog Cal EN (CP-460) to “On” (1) to start calibration.
6. Run the sensor at the operating point for calibration point A. This is generally your smallest
(or negative) voltage point (or smallest current point). Record the value of this operating
point as sensor operating point A in EU.
7. Enter an estimate of the voltage (or current) that the sensor is producing at this operating
point into AnalogRef Val (CP-463). Record this value as point A reference voltage (or
current) along side the sensor operating point A.
8. Set Analog Cal Ref (CP-462) to “B” (2) to select point B.
9. Run the sensor at the operating point for calibration point B. This is generally your largest (or
positive) voltage point (or largest current point). Record the value of this operating point as
point B EU.
10. Enter an estimate of the voltage (or current) that the sensor is producing at this operating
point into AnalogRef Val (CP-463). Record this value as point B reference voltage (or
current) along side the sensor operating point B.
11. Set Analog Cal EN (CP-460) to “Off” (0) to disable further calibration.
12. Go to SCALING/SIGNAL SCALING/P1. Enter voltage (or current) that you recorded as
the point A reference voltage (or current) into AI1 RA (CP-281). Enter the sensor operating
point A (EU) that the sensor was producing during the point A calibration into EU@AI1 RA
(CP-282). This could actually be a time-less unit, but is considered as EU scaling because it
assumes speed representation for the velocity loop. Enter voltage (or current) that you
recorded as the point B reference voltage (or current) into AI1 RB (CP-283). Enter the
sensor operating point B (EU) that the sensor was producing during the point B calibration
into EU@AI1 RB (CP-284).
Repeat this procedure for AI2 if necessary. Calibrate AI2 and use the corresponding AI2 parameters.