Acromag TT231-0600, User Manual, Page: 22 / 41

Model TT231-0600 Two-Wire RTD Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 22 - http://www.acromag.com
- 22 - http://www.acromag.com
Pt RTD Resistance Versus Temperature Table
Note: For Pt385 (Platinum), alpha
= 0.00385Ω/Ω/ºC using the
European curve reference, ITS-90.
For Pt391 (Platinum), Alpha =
0.00391 Ω/Ω/ºC using reference
11-100. Alpha (

) is used to
identify the particular RTD curve.
Alpha (

) is used to identify the
RTD curve and its value is derived
by dividing the sensor resistance at
100ºC (boiling point of water)
minus the sensor resistance at 0ºC
(freezing point of water), by the
sensor resistance at 0ºC, then by
100ºC (

= [R100ºC -R0ºC] / R0ºC/
100ºC). For Pt 100Ω, this is
38.5Ω/100.0Ω/ 100ºC, or
0.00385Ω/Ω/ºC.
The configuration software will
allow you to select the curve
required for your application (i.e.
your alpha value). It uses this value
to calculate the corresponding
input resistance required during
calibration, which it returns to you
in calibration prompt messages.
Refer to the following table when using a resistance substitution box to drive the
input zero and full-scale signals. This contains the resistance values for the two
most common Pt RTD alpha types. Optionally, you can determine resistances using
an online calculator based on a different reference standard,. For example, try the
calculators at
http://www.minco.com/tools/sensorcalc/ .
Platinum RTD Resistance Versus Temperature
Temperature in Ohms
TEMP
100

Platinum RTD

C Pt385 (

=0.00385) Pt391 (

=0.00391)
- 200 18.52 17.26
- 150 39.72 38.79
- 100 60.26 59.64
- 50 80.31 80.00
- 40 84.27 84.03
- 30 88.22 88.04
- 20 92.16 92.04
- 10 96.09 96.02
0 100.00 100.00
+ 10 103.90 103.96
+ 20 107.79 107.91
+ 30 111.67 111.86
+ 40 115.54 115.78
+ 50 119.40 119.70
+ 100 138.51 139.11
+ 150 157.33 158.22
+ 200 175.86 177.04
+ 250 194.10 195.57
+ 300 212.05 213.81
+ 350 229.72 231.76
+ 400 247.09 249.41
+ 450 264.18 266.77
+ 500 280.98 283.84
+ 550 297.49 300.61
+ 600 313.71 317.09
+ 650 329.64 333.29
+ 700 345.28 349.18
+ 750 360.64 364.79
+ 800 375.70 380.10
+ 850 390.48 395.12
Note: Shaded values fall outside the supported zero range for the TT231.