100 ohm at 0 °C
A Pt100 is a platinum element of 100 ohm at 0 °C, a Pt1000 of 1000 ohm. At 100 °C a Pt100 reads 138.51 ohm.
Reference tool — not calibration
Check the sensor before it goes in an RFQ.
Temperature sensor
Ohms to degrees, and the cable colour.
Enter a resistance or a temperature, or switch to the thermocouple. Further down, an offered sensor designation can be checked against it: element, tolerance class, wiring or thermocouple type. The chart and the RFQ line update with every change.
Examples:
Replacement check
On the designations alone: the instrument input, the sheath, the length and the process connection decide.
All 130 engineering tools
A Pt100 resistance thermometer reads 100 ohm at 0 °C, and its resistance rises along the standard IEC 60751 curve. Enter the multimeter reading and the tool gives the temperature and the class tolerance; for a thermocouple, pick the cable colour and it names the type under IEC 60584-3.
The conversion follows the standard’s ideal curve; a real sensor is checked against a reference.
How a sensor is read
Element, class, colour.
Class is the tolerance
Class A (0.15 + 0.002 |t|) °C either way, class B (0.3 + 0.005 |t|) °C; AA is tighter, C looser. The tolerance grows with temperature.
Colour is the thermocouple type
Under IEC 60584-3 the sheath and the positive core carry the type’s colour: K green, J black, T brown, E violet, N pink; the negative is white.
| °C | Pt100, ohm | Pt1000, ohm |
|---|---|---|
| -200 | 18.52 | 185.2 |
| -100 | 60.26 | 602.6 |
| -50 | 80.31 | 803.1 |
| 0 | 100.00 | 1000.0 |
| 50 | 119.40 | 1194.0 |
| 100 | 138.51 | 1385.1 |
| 150 | 157.33 | 1573.3 |
| 200 | 175.86 | 1758.6 |
| 300 | 212.05 | 2120.5 |
| 400 | 247.09 | 2470.9 |
| 500 | 280.98 | 2809.8 |
| 600 | 313.71 | 3137.1 |
| 700 | 345.28 | 3452.8 |
| 800 | 375.70 | 3757.0 |
| Type | Sheath and positive | Legs: positive / negative |
|---|---|---|
| K | Green | nickel-chromium (chromel) / nickel-aluminium (alumel) |
| J | Black | iron / copper-nickel (constantan) |
| T | Brown | copper / copper-nickel (constantan) |
| E | Violet | nickel-chromium (chromel) / copper-nickel (constantan) |
| N | Pink | Nicrosil / Nisil |
| R / S | Orange | platinum-rhodium (13 % Rh for R, 10 % for S) / platinum |
Resistances worked out with the Callendar-Van Dusen equation and the IEC 60751 coefficients. The classes’ validity ranges differ between sources and are not given here.
Sources
IEC 60751 coefficients (A = 3.9083e-3, B = -5.775e-7, C = -4.183e-12): Texas Instruments note SBAA275, Pickering’s platinum sensor note and WIKA data sheet IN 00.29; Pt1000 and the wiring: Wikipedia’s "Resistance thermometer". Class formulas: WIKA, Senmatic, Lapp and Rotronic. Thermocouple colours: TC Direct’s colour code page and WIKA’s TR manual, type E also Farnell’s Labfacility listing; leg materials: Wikipedia’s "Thermocouple".
Before you send the sensor
Questions about temperature sensors in an RFQ
How do I check a Pt100 with a multimeter?
Disconnect it and measure the resistance across the element: 100 ohm at 0 °C, 138.51 ohm at 100 °C. Enter the reading and the tool gives the temperature; in a 2-wire probe the leads add their own resistance to it.
What do classes A and B mean?
How far the element may be from the standard curve, either way: class A (0.15 + 0.002 |t|) °C, class B (0.3 + 0.005 |t|) °C, so at 100 °C class A allows 0.35 °C and class B 0.8 °C. AA is tighter, C looser.
What colour is a type K thermocouple cable?
Under IEC 60584-3 the sheath and the positive core are green and the negative core white. North American and older national codes use other colours, so read the label as well.
What should the request include?
For a resistance thermometer: Pt100 or Pt1000, the class, 2, 3 or 4 wires, the range, the sheath diameter and length and the connection head. For a thermocouple: the type, single or duplex, the diameter, length and range. A photograph of the sensor and its plate helps.
Sensor read?
Send the line with the photograph.
A conversion is a cross-check, not a calibration. Attach photographs of the sensor and its plate, and Vessel Core checks them against each other before an offer goes back.
Buyer tools
