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Rosemount Models 244EH and 244ER PC-Programmable Temperature Transmitters
A-4
Ambient Temperature Effect Transmitters can be installed in locations where the ambient
temperature is between –40 and 85 °C (–40 and 185 °F). At the factory,
each transmitter is individually characterized over this ambient
temperate range. This special manufacturing technique is
accomplished through hot and cold temperature profiling with
individual adjustment factors programmed into each transmitter. The
transmitters automatically adjust for component temperature drift
caused by changing environmental conditions.
When using a Type J thermocouple with a –50 °C to 600 °C
temperature range at an ambient temperature of 60 °C and a reading of
–25 °C, the ambient temperature effect according to °C is: [fixed value
(a) + (% of reading (b) ϫ reading) + (% of span (c) ϫ span)] = [0.006 + (–
0.000025 ϫ (–25)) + (0.00001 ϫ 650)] = 0.013 °C per °C. With the
ambient temperature 40 °C above reference condition temperature, the
total ambient temperature effect is: 40 ϫ 0.013 = 0.52 °C.
When using a Type J thermocouple with a –50 °C to 600 °C
temperature range at an ambient temperature of 60 °C and a reading of
525 °C, the ambient temperature effect according to °C is:[fixed value
(a) + (% of reading (b) ϫ reading) + (% of span (c) ϫ span)] = [0.006 +
(0.0000054 ϫ 525) + (0.00001 ϫ 650)] = 0.015 °C per °C. With the
ambient temperature 40 °C above reference condition temperature, the
total ambient temperature effect is: 40 ϫ 0.015 = 0.6 °C.
The worst case error would be: Reference Accuracy + CJC Accuracy +
Temp Effects = 0.65 °C + 0.5 °C + 0.52 °C = 1.67 °C. Total Probable
Error:
TABLE A-3. Models 244E Ambient Temperature Effects per 1 °C (1.8 °F)
Sensor Options
(1)
Fixed Value % of reading %ofSpan
(if reading > 0) (if reading is < 0)
2-, 3-, 4-wire RTDs
PT 100 (α = 0.00385) 0.003 °C — — +0.001% of span
Pt 100 (α = 0.003916) 0.003 °C — — 0.001% of span
Pt 200 0.004 °C — — 0.001% of span
Pt 500 0.003 °C — — 0.001% of span
Pt 1000 0.003 °C — — 0.001% of span
Ni 120 0.003 °C — — 0.001% of span
Cu 10 0.03 °C — — 0.001% of span
Thermocouples
Type B (100 °C ≤ reading <300°C) 0.064 °C –0.011 — 0.001% of span
(300 °C ≤ reading < 1000 °C) 0.040 °C –0.025 — 0.001% of span
(reading ≥ 1000 °C) 0.014 °C — — 0.001% of span
Type E 0.005 °C –0.00043 –0.0043 0.001% of span
Type J, K, DIN L 0.006 °C –0.00054 –0.0025 0.001% of span
Type N 0.007 °C –0.00036 — 0.001% of span
Type R, S (reading < 200 °C) 0.023 °C –0.0036 — 0.001% of span
(reading ≥ 200 °C) 0.016 °C — — 0.001% of span
Type T, DIN U 0.007 °C — –0.043 0.001% of span
Type W5Re/W26Re 0.023 °C –0.0036 — 0.001% of span
0.016°C —
Millivolt Input 0.0005 mV — — 0.001% of span
2-, 3-, 4-wire Ohm 0.0084 Ω — — 0.001% of span
(1) Change in ambient is with reference to the calibration temperature of the transmitter 68 °F (20 °C) from factory.
0.65
2
0.5
2
0.52
2
++ 0.97°C=