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Resistance Temperature Detectors / RTD / RTDs
What is a Resistance Temperature Detector? Resistance Temperature Detectors (RTD), as the name implies, are sensors used to measure temperature by correlating the resistance of the RTD element with temperature. Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core. The element is usually quite fragile, so it is often placed inside a sheathed probe to protect it.
The RTD element is made from a pure material whose resistance at various temperatures has been documented. The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.
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Common Resistance Materials for RTDs:
Platinum (most popular and accurate)
Nickel
Copper
Balco (rare)
Tungsten (rare)
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 Benefits of Using an RTD |
The RTD is one of the most accurate temperature sensors. Not only does it provide good accuracy, it also provides excellent stability and repeatability.
Most OMEGA standard RTDs comply with DIN-IEC Class B. The accuracy of an OMEGA standard RTDs is shown in the
table on the right.
RTDs are also relatively immune to electrical noise and therefore well suited for temperature measurement in industrial environments, especially around motors, generators
and other high voltage equipment.
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Accuracy for Standard OMEGA RTDs
Temperature
°C | Ohms | °C |
| -200 | ±056 | ±1.3 |
| -100 | ±0.32 | ±0.8 |
| 0 | ±0.12 | ±0.3 |
| 100 | ±0.30 | ±0.8 |
| 200 | ±0.48 | ±1.3 |
| 300 | ±0.64 | ±1.8 |
| 400 | ±0.79 | ±2.3 |
| 500 | ±0.93 | ±2.8 |
| 600 | ±1.06 | ±3.3 |
| 650 | ±1.13 | ±3.6 |
| 700 | ±1.17 | ±3.8 |
| 800 | ±1.28 | ±4.3 |
| 850 | ±1.34 | ±4.6 |
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| Styles of RTDs |
RTD Elements
The RTD element is the simplest form of RTD. It consists of a piece of wire wrapped around a ceramic or glass core.
Because of their compact size, RTD elements are commonly used when space is very limited.
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RTD Surface Elements
A surface element is a special type of RTD element. It is designed to be as thin as possible thus providing good contact
for temperature measurement of flat surfaces.
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RTD Probes
The RTD probe is the most rugged form of RTD. A probe consists of an RTD element mounted inside a metal tube, also known as a
sheath. The sheath protects the element from the environment. OMEGA offers a wide variety of probes in various configurations.
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