Watlow Ltd- Reference - Guides and Tutorials

Temperature Sensor Comparison Guide

Temperature Sensor Attributes
Criteria	Thermocouple	RTD	Thermistor
Cost-OEM Quality	Low	High	Low
Temperature Range	Very wide -450°F +4200°F	Wide -400°F +1200°F	Shot to medium -100°F +500°F
Interchangeability	Good	Excellent	Poor to fair
Long-term Stability	Poor to fair	Good	Poor
Accuracy	Medium	High	Medium
Repeatability	Poor to fair	Excellent	Fair to good
Sensitivity (output)	Low	Medium	Very high
Response	Medium to fast	Medium	Medium to fast
Linearity	Fair	Good	Poor
Self Heating	No	Very low to low	High
Point (end) Sensitive	Excellent	Fair	Good
Lead Effect	High	Medium	Low
Size/Packaging	Small to large	Medium to small	Small to medium

Temperature Sensor Advantages and Disadvantages
Sensor	Advantages	Disadvantages
Thermocouple	No resistance leadwire problems Fastest response Simple, rugged Inexpensive High temperature operation Point temperature sensing	Non-linear Low voltage Least stable, repeatable Least sensitive
RTD	Most stable, accurate Contamination resistant More linear than thermocouple Area temperature sensing Most repeatable temperature measurement	Expensive Current source required Self-heating Slow response time Low sensitivity to small temperature changes
Thermistor	High output, fast Two-wire ohms measurement Economic Point temperature sensing	Non-linear Limited range Fragile Current source required Self heating

Watlow Ltd Linby Industrial Estate, Linby, Nottingham, NG15 8AA +44 115 964 0777 Fax - +44 115 964 0071