Product Info

iTEMP TMT142
10 Endress+Hauser
Sample calculation with Pt100, measuring range 0 to +200 °C (+32 to +392 °F), ambient temperature
+35 °C (+95 °F), supply voltage 30 V:
Measured error digital = 0.04 °C + 0.006% x (200 °C - (-200 °C)): 0.11 °C (0.20 °F)
Measured error D/A = 0.03 % x 200 °C (360 °F) 0.06 °C (0.11 °F)
Influence of ambient temperature (digital) = (35 - 25) x (0.0013 % x 200 °C -
(-200 °C)), min. 0.003 °C
0.05 °C (0.09 °F)
Influence of ambient temperature (D/A) = (35 - 25) x (0.003% x 200 °C) 0.06 °C (0.11 °F)
Influence of supply voltage (digital) = (30 - 24) x (0.0007% x 200 °C - (-200 °C)),
min. 0.005 °C
0.02 °C (0.04 °F)
Influence of supply voltage (D/A) = (30 - 24) x (0.003% x 200 °C) 0.04 °C (0.72 °F)
Measured error digital value (HART):
√[(Measured error digital² + Influence of ambient temperature (digital)² +
Influence of supply voltage (digital)²]
0.13 °C (0.23 °F)
Measured error analog value (current output):
√[(Measured error digital² + Measured error D/A² + Influence of ambient
temperature (digital)² + Influence of ambient temperature (D/A)² + Influence of
supply voltage (digital)² + Influence of supply voltage (D/A)²]
0.16 °C (0.29 °F)
The measured error data correspond to 2 s (Gaussian distribution).
Physical input measuring range of sensors
10 to 400 Ω Cu50, Cu100, polynomial RTD, Pt50, Pt100, Ni100, Ni120
10 to 2 000 Ω Pt200, Pt500
–20 to 100 mV Thermocouples type: A, B, C, D, E, J, K, L, N, R, S, T, U
Sensor adjustment Sensor-transmitter-matching
RTD sensors are one of the most linear temperature measuring elements. Nevertheless, the output
must be linearized. To significantly improve temperature measurement accuracy, the device allows
the use of two methods:
• Callendar-Van Dusen coefficients (Pt100 resistance thermometer)
The Callendar-Van Dusen equation is described as:
R
T
= R
0
[1+AT+BT²+C(T-100)T³]
The coefficients A, B and C are used to match the sensor (platinum) and transmitter in order to
improve the accuracy of the measuring system. The coefficients for a standard sensor are specified
in IEC 751. If no standard sensor is available or if greater accuracy is required, the coefficients for
each sensor can be determined specifically with the aid of sensor calibration.
• Linearization for copper/nickel resistance thermometers (RTD)
The polynomial equation for copper/nickel is as follows:
R
T
= R
0
(1+AT+BT²)
The coefficients A and B are used for the linearization of nickel or copper resistance thermometers
(RTD). The exact values of the coefficients derive from the calibration data and are specific to each
sensor. The sensor-specific coefficients are then sent to the transmitter.
Sensor transmitter matching using one of the methods explained above significantly improves the
temperature measurement accuracy of the entire system. This is because the transmitter uses the
specific data pertaining to the connected sensor to calculate the measured temperature, instead of
using the standardized sensor curve data.
1-point adjustment (offset)
Shifts the sensor value
Current output adjustment
Correction of the 4 and/or 20 mA current output value.