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9.5.3. Thermal Sensors, Power
Problem
Cause/Remedy
Instrument shows zero
reading in both power
and energy modes.
Check connections between the sensor
and the instrument. (See section
9.6.1.1). Check that the sensor disc is
operative. Resistance between the
pins 1 and 9 of the sensor connector
should be about 11k. If the sensor is
defective, there will be an open or
short circuit.
Instrument responds
while sensor is cold,
but suddenly fails as it
heats up.
Replace sensor disc. See Section-
9.6.1.2
Instrument does not
return completely to
zero
on
power
measurement.
If sensor is very hot, allow it to cool.
Disconnect the sensor from the
instrument. If readout unit does not
zero, follow instructions in section
3.5.5. If the offset persists, try zeroing
with the sensor connected as well, as
described in the same section.
9.5.4. Pyroelectric Sensors
Problem
Cause/Remedy
Instrument reads
incorrectly or erratically,
especially on sensitive
scale.
Possible
electromagnetic
interference from pulsing laser is
causing misreading and/or false
triggering
Instrument triggers even
without being exposed to
laser pulses.
Check the following:
Sensor is mounted to stand using
insulated plastic rod provided with
instrument, and not metal rod.
Instrument shows
frequency which is too
high
1. Try keeping cable away from
bench.
2. Move sensor/display further away
from EMI.
