tekmar 078 Universal Sensor - Manual (Page 2)

© 2009 D 078 - 04/09 2 of 4
STEP TWO
WIRING AND TESTING THE SENSOR
Caution: Do not run sensor wires parallel to telephone or power cables. If the sensor
wires are located in an area with strong sources of electromagnetic interference, shielded
cable or twisted pair should be used or the wires can be run in a grounded metal conduit.
If using shielded cable, the shield wire should be connected to the Com Sen terminal on
the control and not to earth ground.
•• If a Universal Sensor Enclosure 080 is used to mount the 078, follow the installation
instructions provided in the Data Brochure D 080.
•• Without the Universal Sensor Enclosure 080, it is necessary to connect 18 AWG wire to
the two sensor wires. Wire nuts can be used to hold the wires together.
•• Follow the sensor testing instructions given in this brochure and then connect the wires
to the control.
Sensor Testing Instructions
A good quality test meter capable of measuring up to 5,000 kΩ (1 kΩ = 1000Ω) is required to
measure the sensor resistance. In addition to this, the actual temperature must be measured
with either a good quality digital thermometer, or if a thermometer is not available, a second
sensor can be placed alongside the one to be tested and the readings compared.
First measure the temperature using the thermometer and then measure the resistance of
the sensor at the control. The wires from the sensor must not be connected to the control
while the test is performed. Using the chart on the following page, estimate the temperature
measured by the sensor. The sensor and thermometer readings should be close. If the test
meter reads a very high resistance, there may be a broken wire, a poor wiring connection
or a defective sensor. If the resistance is very low, the wiring may be shorted, there may be
moisture in the sensor or the sensor may be defective. To test for a defective sensor, measure
the resistance directly at the sensor location.
Do not apply voltage to a sensor at any time as damage to the sensor may result.