1. Temperature Back to Basics RTDs (Resistance Temperature Detectors)

2. Introduction Types of sensors Specifications ASTM vs. IEC-60751
RTD needs, findings and calibration
ITS-90 Coefficients using of multiple Pt tables
Smart connectors

3. Types of sensors

4. RTD Sensor Types Copper Very linear with a very limited range Nickel
Most sensitive but least linear
Platinum
Linear wide range most commonly used

5. RTD Sensor Types Thin Film Wire Wound
Thin Layer of Platinum on a substrate
Trimmed to specific resistance
Protective coating
Wire Wound
Coil of wire
Ceramic of Glass tube

6. RTDs
, 3, and 4 Wire (leads)
Probe
Surface
Approximately -200 to 850°C

7. RTDs Platinum .392 ohms/°C 25.5 ohms @ 0°C
Copper .427 ohms/°C °C
Copper .427 ohms/°C °C
Nickel ohms/°C °C
Nickel ohms/°C °C

8. Specifications ASTM 1137 vs. IEC-60751

9. ASTM 1137 & IEC60751 ASTM 1137 Classifications
Class A ±[ |t| ]°C
Class B ±[ |t| ]°C
IEC60751
Class A ±[ |t| ]°C
Class B ±[ |t| ]°C

10. ASTM vs. IEC60751 ASTM Class A ±[0.13 + 0.0017|t| ]°C IEC60751
(100°C X .0017) = 0.3
IEC60751
Class A ±[ |t| ]°C
(100°C X .002) = 0.35
100°C = .05°C

11. RTD Needs, Findings and Calibration

12. Replace Thermocouples with RTDs
Type of RTD Needed
4 wire
ASTM 1137 Class A
Range -80 to 250°C
Flexible for use in chambers
Short probe
ITS-90 Coefficients

13. Tolerances ASTM 1137 Class A -80°C ±.226°C -50°C ±.215°C -38°C ±.195°C
Example 100 x = .3
-80°C ±.226°C
-50°C ±.215°C
-38°C ±.195°C
0°C ±.13°C
100°C ±.3°C
250°C ±.555°C

14. Search for Coefficients
None found for ITS-90 ranges
Found CVD (Callendar-Van Dusen)
Found many tables for alpha

15. RTDs and the ITS-90
There isn’t a resistance vs. temperature relationship for RTDs in the ITS-90 as there is with ASTM 1137 and IEC 60751
There are no classification tolerances for RTDs in the ITS-90 as there is with ASTM 1137 and IEC 60751

16. ITS-90 Ranges Used Range 4 -189.8344°C to .01°C
Range -80°C to 250°C Desired
Range °C to .01°C
Range °C to °C
Characterized RTD
Comparison Tested, Cycled, Drift Checked

17. Verification of RTDs Characterization method used Treat them as PRTs
Use ITS-90 range 4 & 8
Check drift of each
Increased accuracy
Accuracy of ±0.05°C Possible
Drawbacks
Calculation of coefficients
Tolerance condition by checking drift.
Update coefficients in read outs
Too much time wasted!

18. Tables to Coefficients
Vendor Tables compared to ASTM 1137
ASTM tables and decimal places
Increased decimal places by using (RTD Calc) from Minco
ITS-90 Range 4 and 8 coefficients created

19. Coefficient Calculation
Example of TableWare
TableWare used with permission of Hart Scientific

20. RTD Coefficients RTPW: 100.003989 Low Range High Range
a4 = E a8 = E-02
b4 = E b8 = E-04
Temperature Range of -80 to 250°C

21. Testing of the Coefficients
Enter coefficients into Hart Scientific 1590 Super Thermometer.
Used a decade box that was standardized with the 1590 (1.55ppm)
Decade was connected in a 4 wire connection
1590 was switch from reading resistance to temperature via the coefficients
Used with permission of Hart Scientific

22. Testing Data Test Point Reading -80°C -80.001 0°C -.006 100°C 100.004

23. Verification of RTDs Drawbacks Tolerance Testing Method Less accurate
Faster turn around time
Universal coefficients
Reduce or eliminated programming of coefficients

24. Verification Setup Hart Scientific 1590 with 2590 mux (Read out)
Hart Scientific 5628 PRT (Reference probe)
Hart Scientific 7380, 7025, 6050H (Baths)
Hart Scientific MetTemp II (Software)
Used with permission of Hart Scientific

25. Where else can this information be used?
Smart Connectors that store the coefficients of the probe.
Multi and single channel read outs

26. WHAT IS THE EQUATION ERROR?
Generic Digital Read Outs
Typical website Specifications
Range
Resolution
Accuracy
Probe # of wires
Display
Dimensions
Typical Manual Specifications
Range
Resolution
Accuracy
Probe # of wires
Display
Sensitivity (alpha) ,
WHAT IS THE EQUATION ERROR?

27. Smart connectors
Used with permission of Hart Scientific

28. Digital Read Outs Type of Read out Needed 4 wire Connection
Medium to High accuracy
RTD/PRT/ Thermistor
Be able to use coefficients
Data dump or PC connection
Used with permission of Hart Scientific

29. Surface Probe with Smart Connector

30. Questions?