RTD (Resistance Temperature Detector)

RTD (Resistance Temperature Detector)

RTD Features

·         Used for measurement of temperature

·         Linear Transducer (less linear than LM 35)

·         Positive temperature coefficient (Resistance increase as temperature increase)

·         Resistance type transducer

·         Passive Transducer

·         Required  bridge circuit  for signal conditioning circuit

·         Range (*): -250⁰C to + 850⁰C (different ranges given in different books)

Materials:

·        • Platinum (most popular and accurate)

• Nickel
• Copper
• Balco (rare)

• Tungsten (rare)
* PT-100 meaning: value of resistance 100 ohms at 0 degree C
Characteristics: 

(Ref: http://www.electrical4u.com/resistance-temperature-detector-or-rtd-construction-and-working-principle/

Equations: 

R = R0(1+alpha*(t-t0));
where, R is the resistance at t degree C, R0 is the resistance at t0 degree C and alpha is temperature coefficient of RTD.(+ve).

Signal Conditioning of RTD:  Wheatstone bridge (small change of resistance)

(Ref: http://www.electrical4u.com/resistance-temperature-detector-or-rtd-construction-and-working-principle/)

Issues: 

1. Self-heating