Campbell CR3000 Micrologger, Руководство оператора

Страница: 363 / 644

Section 8. Operation
363
Conditions
CR3000 module temperature, –25 to 50 °C
Temperature = 1300 °C
Reference temperature = 25 °C
Delt
a T (temperature difference) = 1275 °C
Thermocouple output multiplier at 1300 °C = 34.9 µV °C
-1
Thermocouple output = 1275 °C • 34.9 µV °C
-1
= 44500 µV
Input range = ±200 mV
Error Calculations with Input Reversal = True
µV error = gain term + offset term
=
(44500 µV * 0.07%) + (1.5 * 6.67 µV + 1.0 µV)
= 31.2 µV + 11.0 µV
= 42.2 µV (= 1.21 °C)
Error Calculations with Input Reversal = False
µV error = gain term + offset term
= (44500 µV * 0.07%) + (3 * 6.67 µV + 2.0 µV)
= 31.2 µV + 22.0 µV
= 1.52 µV (= 1.52 °
C)
Ground Looping Error
When the thermocouple measurement junction is in electrical contact with the
object being measured (or has the possibility of making contact), a differential
measurement should be made to avoid ground looping.
Noise Error
The typical input noise on the ±20 mV range for a differential measurement with
16.67 ms integration and input reversal is 0.19 μV RMS. On a type
-T
thermocouple (approximately 40 μV/
°
C), this is 0.005
°
C.
Note This is an RMS value; some individual readings will vary by greater
than this.