APG IRU-9400 user manual - Manual (Page 25)

Rev. B1, 3/10 IRU Series
25
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• Using External Temperature Compensation
A correction factor for changes in temperature can be applied to the sensor
readings using an external temperature probe in conjunction with a PLC.
Applying a correction formula to the sensor output may achieve better results
than using the internal temperature compensation in some applications.
The formula for the change in the speed of sound is:
((T1 - T2 + 273)/273)^0.5
T1 = present temperature in °C
T2 = temperature when sensor was calibrated.
There are two approaches for using the correction formula. One uses the factory
calibration with the sensor’s multiplier set to 1.00. The factory calibration
is based on a temperature of 25°C. Therefore, T2 will equal 25. The second
approach is to calibrate the sensor as outlined in the multiplier section then apply
the temperature correction. In this case, T2 becomes the temperature at the time
of calibration.