Unit installation

H-1

Appendix H: Using the LM335 Temperature Sensor

The RLC-3 supports the National Semiconductor LM335Z temperature sensor. The sensor

converts temperature into voltage. This voltage is read by the controllers ADC (Analog-Digital

Convertor) which allows the controller to read a voltage. When using the LM335Z sensor, the

sensor needs to be powered in order for the temperature to be read. Powering the sensor is

accomplished by turning the appropriate dip switch 'ON' on the I/O board. There are two packs of

8 switches, one pack for power and and one for the voltage dividers. The power switch must be on

and the voltage divider switch off for the temperature sensor to work.

LM335Z Temperature Probe Connections Diagram

- If you have your temperature sensor hooked up backwards (+OUT switched with the -GND) you

will read ~0.6 volts across the sensor.

- Verify the appropriate resistor divider switch is OFF, and sensor power switch is ON. These

switches provide the power and control for the LM335Z.

- Voltage meter reading at the sensor measure: Temperature Celcius = (voltage*100)-273