APG IRU-3000 user manual - Manual (Page 14)

IRU-2xx4/3xx4 Rev. A2, 11/08
14
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CALIBRATION
Calibration The IRU-2XX4/3XX4 must be calibrated if a familiar reading is
desired. The software is designed so that a calibration factor of 1000 will yield
units that represent inches, feet and meters. Variations of the speed of sound in
different atmospheres may yield readings which slightly differ from actual
measured values. If this is unacceptable, vary the Calibration factor to “dial in”
the exact number desired.
Acceptable values for this parameter range from 0100 to 1999
If a certain distance to a target is known and the sensor is not outputting the
desired reading, use the following formula to obtain the desired reading.
New Calibration Factor = (Desired Distance Reading x Old Calibration Factor) /
Sensor Distance Reading.
Example: Suppose a target is 5.50 feet from the face of the sensor. The sensor
has a calibration factor of 1000 and is yields a Distance Reading of 5.65 ft.
Calculate the new Calibration Factor by:
New Calibration Factor = (5.50 x 1000) / 5.65 = 0973.
To read the calibration factor in a sensor, use the command structure:
Send Receive
AAh Start Byte 66h Start Byte
01h, Sensor Number 01h Sensor Number
0Bh Command 0Bh Command
00h Data (not used) 03h Calibration (High Byte)
00h Data (not used) E8h Calibration (Low Byte)
55h End Byte ##h NA
99h Stop Byte
To change the calibration factor in a sensor, use the command structure;
Send
AAh
Start Byte
01h, Sensor Number
0Ch Command
03h Data (not used) 0973 D = 3CD
CDh Data (not used)
55h End Byte