Ametek Land LMG MkII, User Manual

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User Guide 6 - 22
Signal Processor LMG MkII
6.6.3 Background Compensation
Configuration of the LMG MkII to perform this function is covered in
Section 6.4.6.
This function provides a correction for background reflection and load
emissivity. It is available on the following thermometer ranges M2, M3, M4,
M5, M6, M7, M8, VDT and FTS.
It is not recommended that Background Compensation be used on short
wavelength thermometers.
NOTE
Channels to be used MUST have their emissivity values set to
e
= 1.00
otherwise significant errors in reading true temperature will occur.
If an input from a background sensing thermocouple is to be accepted into
an LMG MkII, then:
• the LMG MkII must have an I/O card fitted which is allocated to
accepting the thermocouple transmitter input
• the thermocouple’s characteristic non-linear output must be
linearised and converted to a 4 to 20mA signal, equivalent to one
of the LMG MkII pre-determined linear input ranges, before being
transmitted to the LMG MkII
i.e. 0 to 600°C 30 to 1100°F
0 to 1100°C 30 to 2000°F
0 to 1600°C 30 to 3200°F
Compensation Examples
R or S Type
Thermocouple
Secondary Input
(Background Temp)
LMG Processor
3.9µm
Thermometer
Primary Input
(Apparent Load Temp)
True Load Temp
Note:
Thermocouple must be connected to
LMG via suitable linear 4 to 20mA
transmitter ranged appropriately
Fig. 6-22 Schematic showing 1x thermometer and 1x thermocouple in system