PASCO CI-6628 INFRARED SENSOR - Manual

10 1
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GAIN
TARE
INFRARED SENSOR
CI-6628
Instruction Sheet for the
PASCO
Model CI-6628
INFRARED SENSOR
012-06915B
© 1999 PASCO scientific
shutter bracket CI-6628
Infrared Sensor
unit
to computer
interface
cable with DIN
connectors
mounting
thumbscrew
with washer
Introduction
The sensing element used in the PASCO CI-6628
Infrared Sensor is a thermopile. Thermopile
detectors are voltage-generating devices that can
be thought of as a miniature array of
thermocouples. The thermopile is a high output,
thin film, silicon based device which has 48
thermopile junctions. The active or ‘Hot’ junctions
are blackened to efficiently absorb radiation. The
reference or ‘Cold’ junctions are maintained at the
ambient temperature of the detector
The blackening material used on the ‘Hot’
junctions is capable of absorbing radiant energy
from ultra violet to the far infrared. In order to
limit the spectral sensitivity, optical filters and
windows may be placed in front of the detector.
The window installed in the detector is a ruby-
based material which has a spectral response from
visible light to the far infrared (about 40,000 nano-
meters). The hermetically sealed detector is heat
treated and filled with argon gas to improve long
term stability.
The absorption of radiation by the blackened area
causes a rise in temperature in the ‘hot’ junctions as
compared to the ‘cold’ junctions of the thermopile.
This difference in temperature across the
thermocouple junction causes the detector to
generate a positive voltage. If the active or ‘hot’
junction were to cool to a temperature less than the
reference or ‘cold’ junction the voltage output
would be negative.
The output of the thermopile detector is presented
to a gain selectable amplifier. The GAIN switch
located on the top of the sensor is used to adjust the