Page 12.1
12.
APPENDS
12.1. Measurement accuracy for thermocouple
The thermocouple measurements are treated as voltage measurements.
For a given range of temperature measurement, the software calculates the voltage caliber
the following way:
* Let « T » the absolute value of the max. measurable value, in °C
* Add 40°C to take the max. cold welding temperature into account
* Search the corresponding voltage value U in the table of thermocouples
* Program the caliber with U included in the range.
Example:
You want to program a measurement range between -50 and + 50°C with a J
thermocouple:
Max. absolute value
T = 50°C
Add 40°C
T + 40 = 90°C
Corresponding U voltage according to the tables ThJ
U = 4.726 mV
Programmed caliber: 10 mV (measurement range: -5mV to +5mV)
The measurement inaccuracies below are max. values: the typical values are half to thrice as
much.
The temperature measurement accuracy is the sum of several possible uncertainty causes:
Pl: linearization accuracy
Ps: weld welding accuracy
Pm: measurement accuracy of the equivalent voltage
The total accuracy Pt is then: Pt = Pl + Ps + Pm
For the recorder:
Pl = + 0.25°C for all thermocouples
Ps = + 0.5°C for all thermocouples
Pm = 0.1% of the voltage range + 10µV) divided by the slope of the thermocouple in
µV/°C
Summary of Contents for DAS220
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