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| | | Application Guid | | |
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| | | RTDs generally have a positive temper- be taken into account. Ideally the | | |
| | | The Art of Temperature Sensing RTDs are industrial temperature sensors utilizing metals known and predictable change in electrical resistance based on a rise or fall in temperature. The sensing element is a deposited film or coil of wire, usually platinum, nickel, copper, or nickel-iron. | | |
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| | | ature coefficient. RTDs are powered devices. The instrument receiving their "signal" reads temperature as the change in voltage. Looked at another way, as temperature changes, so does the sensor's resistance. Because these are resistance devices, their operation generates heat in addition to the heat they're measuring. When specifying the use of an INDUSTRIAL RTD, its mass and self-generated heat must | | |
| | | substance being measured will have enough mass and thermal conductivity so as to make the RTD's self-generated heat a negligible factor. | | |
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| | | RTD Interchangeability Interchangeability is a commonly cited factor of RTD accuracy. It tells how closely the sensing element of an RTD follows its nominal resistance/temperature curve, and the maximum variation that should exist in the readings of identical sensors, mounted side-by-side under identical conditions. Interchangeability consists of both a tolerance at one reference temperature, usually 0°C, and a tolerance on the slope, or Temperature Coefficient | | of Resistance (TCR). Even a slight deviation in the TCR will cause a significant error to result at elevated Ref. 31 | | temperatures. Thus, it's important for the user to specify the TCR when ordering RTD probes. | | |
| | | (D 3 (D 0> c | | |
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| | | | | | | | | | | | Element Type | Temperature Range | Base Resistance | TCR(Q/Q/°C) | | | | *Platinum DIN HCopper HNickel | -200 to 650°C (-330 to 1200°F) -100 to 260°C (-150 to 500°F) -100 to 205°C (-150 to 400°F) | 100Q at 0°C 10Q at 25°C 120Q at 0°C | 0.00385 0.00427 0.00672 | | | | | | | | | | | |
| | | (D 3 (A O | | |
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| | | *Thin film element -50 to 550°C (-58 to 1020°F). | | |
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| | | Table of Tolerance Values - Ref. 32 | | |
| | | RTD Tolerance Class Definitions DIN/IEC class A: ±(0.15 + 0.002 |t|°C DIN/IEC class B: ±(0.30 + 0.005 |t|°C | | |
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| | | | | | | | | | | | | | | | Resistance | Tolerance DIN-IEC-751 | | | | Temperature | Value | Class A | Class B | | | | °C | | Q | °C (Q) | °C (Q) | | | | -200 | (-328) | 18.52 | ±0.55 | (±0.24) | ±1.3 | (±0.56) | | | | -100 | (-148) | 60.26 | ±0.35 | (±0.14) | ±0.8 | (±0.32) | | | | 0 | (32) | 100.00 | ±0.15 | (±0.06) | ±0.3 | (±0.12) | | | | 100 | (212) | 138.51 | ±0.35 | (±0.13) | ±0.8 | (±0.30) | | | | 200 | (392) | 175.86 | ±0.55 | (±0.20) | ±1.3 | (±0.48) | | | | 300 | (572) | 212.05 | ±0.75 | (±0.27) | ±1.8 | (±0.64) | | | | 400 | (752) | 247.09 | ±0.95 | (±0.33) | ±2.3 | (±0.79) | | | | 500 | (932) | 280.98 | ±1.15 | (±0.38) | ±2.8 | (±0.93) | | | | 600 | (1112) | 313.71 | ±1.35 | (±0.43) | ±3.3 | (±1.06) | | | | 650 | (1202) | 329.64 | ±1.45 | (±0.46) | ±3.6 | (±1.13) | | | | | | | | | | | | | | |
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| | | Where t is the actual temperature, in °C, of the platinum elements. | | |
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