ILX Lightwave LDT-5525 User Manual page 59

Appendix C
AD590 and LM335 Sensor Calibration
Introduction
The LDT-5525 Temperature Controller uses two constants (C1 and C2) for calibrating linear thermal sensing devices,
such as the AD590, and the LM335. C1 is used as the linear or zero offset value, and C2 is used as the slope or gain
adjustment. Therefore, C1 should be set to a nominal value of 0, and C2 should be set to a nominal value of 1, when
the SENSOR SELECT switch is in the AD590, or LM335 positions.
In order to calibrate a linear sensor device, the sensor must be operated at an accurately known, stable temperature.
For example, the sensor may be calibrated at 0°C if the sensor is placed in ice water until its temperature is stable. A
highly accurate temperature probe, thermometer, environmental chamber, etc., may also be used to determine the
known temperature for calibration. This appendix contains one and two point calibration methods for linear sensor
devices. These methods will work for either type of device.
AD590 Sensor
The AD590 is a linear thermal sensor which acts as a constant current source. It produces a current, i, which is
directly proportional to absolute temperature, over its useful range (-50°C to +150°C). This nominal value can be
expressed as:
i = 1uA / K
where i is the nominal current produced by the AD590, and K is in Kelvin.
C-1