Termaline® Load Resistor
9
RF Assembly Resistance Test
Note:
These tests are by no means a necessity to the operation of the
load
but merely guidelines for
the users information.
Accurate measurement of the DC resistance between the inner and outer conductors of the RF input connector will
provide a good check of the condition of the load resistor.
Checking the DC resistance is simply used to measure a change in the resistance over time. Tracking the DC
resistance should start
before
the unit is first put into service. Perform the following steps and record the value for
future comparison. Resistance measurements should be taken periodically according to use.
Preparation:
Tools: Common hand tools.
Ohmmeter with an accuracy of ± 1% at 50 ohms (or use a resistance bridge).
Use low resistance leads, preferably a short piece of 50 ohm coaxial cable fitted with an appropriate
connector or alligator clips.
Temperature of the load should be stabilized between 20°C to 25°C (68°F to 77°F).
DC Resistance Measurement
Note:
It is recommended that this resistance check be performed each time the load is to be used.
1.
Turn off RF power and interlock circuitry before making any disconnections.
2.
Disconnect the RF coaxial line.
3.
Connect the multimeter test leads across the center and outer conductor of the load resistor. See
4.
Record the value of the resistance
before
the load is put into service. Compare subsequent values with the
latest reading. If the values vary more than 2 ohms this could be an indication of a failing resistive element.
Figure
1
Measuring DC Resistance
WARNING
Never attempt to connect or disconnect RF equipment from the transmission
line while RF power is being applied.
Leaking RF energy is a potential health hazard.
