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Thermometer
User Guide
CDA
5 Electrical Connections
5.1 Thermometer Operation
The LAND Incinerator Thermometer is a rugged, stand alone, non contact
thermometer, designed for measuring relatively low temperatures in hostile
environments. It has a temperature measurement range of 400 to
1800°C/752 to 3272°F.
The thermometer operates on a simple 4 to 20mA current loop. A block
diagram of the key features of the thermometer is shown in Fig. 11.
The thermometer is contains an integral lens, which focuses infrared radiation
from a predefined target area onto an infrared detector. This detector
converts the incoming infrared radiation into a low level electrical voltage
which is proportional to the temperature of the target. This electrical voltage
is then amplified, corrected for emissivity and linearized to produce an analog
4 to 20mA current output.
Fig. 11 - Thermometer block diagram
294011
Incoming
infrared
radiation
from
target spot
Lens
Infrared
detector
Amplifier
Lineariser
Emissivity
Speed of
Response
4 to 20mA
Driver
Current
loop
In normal operation the 4-20mA output is designed to stay within the
‘saturation’ range as defined by NAMUR NE43.
Fail High -
>= 21.0mA
Saturation High - 20.5mA
Signal Range -
4-20mA
Saturation Low - 3.8mA
Fail Low -
<= 3.6mA
Summary of Contents for CDA
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