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Temperature-dependent resistor (Pt100/ Pt1000)

Platinum measuring resistor

A platinum measuring resistor is a resistance thermometer used to measure temperature. The most commonly applied platinum resistance thermometers are Pt100 and Pt1000. The designations Pt100/Pt1000 describe the resistor material involved, in this case platinum, and its nominal resistance R0 at a temperature of 0 °C. (R0,Pt100 = 100 Ω / R0,Pt1000 = 1 kΩ). Usually Pt100 and Pt1000 are used, although other resistance values are possible.

Resistance thermometers: Design

A platinum resistance thermometer consists of an electrical resistance of platinum. Platinum is often used for temperature changes due to its constant electrical properties. The resistor is connected to the connecting wires by an electrical conductor. The components are protected against external influences by a protective housing and appropriate insulation.

Resistance thermometers: How they work

A constant current flows via the connecting cables through the resistance thermometer. An electrical voltage is measured between the two connecting cables which depends on the platinum resistance. The linear correlation between the electrical resistance of the platinum conductor and the temperature is used to measure the temperature. If the temperature rises, so too does the electrical resistance. As a result, a different voltage is also measured between the conductors, which is used to calculate the temperature.
“The linear correlation between the electrical resistance of the platinum conductor and the temperature is used to measure the temperature.”

 

Resistance thermometer characteristic curve

The characteristic curve shows the linear relationship between electrical resistance and temperature. Exact values for Pt100 and Pt1000 can be determined graphically from the Pt100 characteristic curves / Pt1000 characteristic curves or read directly from the Pt100 table / Pt1000 table. Platinum is highly suitable as a material due to its high long-term stability and particularly constant electrical properties at high temperatures. Thus, the characteristic curve for platinum resistors is very linear even at high temperatures. By adding other impurities to platinum, even better results are achieved in this respect.

 

 

 

Pt100 characteristic curve

 

Diagram Pt100 characteristic curve

 

 

Resistance table Pt100

Show/Hide Pt100 table

 

Temperature
Resistance
Tolerance class B
Tolerance class A
°C
Ω
in ± °C / in ± Ω
in ± °C / in ± Ω
-40
84.27
0.5 / 0.2
0.23 / 0.09
-30
88.22
0.45 / 0.18
0.21 / 0.08
-20
92.16
0.4 / 0.16
0.19 / 0.07
-10
96.09
0.35 / 0.14
0.17 / 0.07
0
100
0.3 / 0.12
0.15 / 0.06
10
103.9
0.35 / 0.14
0.17 / 0.07
20
107.79
0.4 / 0.16
0.19 / 0.07
30
111.67
0.45 / 0.17
0.21 / 0.08
40
115.54
0.5 / 0.19
0.23 / 0.09
50
119.4
0.55 / 0.21
0.25 / 0.1
60
123.24
0.6 / 0.23
0.27 / 0.1
70
127.08
0.65 / 0.25
0.29 / 0.11
80
130.9
0.7 / 0.27
0.31 / 0.12
90
134.71
0.75 / 0.29
0.33 / 0.13
100
138.51
0.8 / 0.3
0.35 / 0.13
110
142.29
0.85 / 0.32
0.37 / 0.14
120
146.07
0.9 / 0.34
0.39 / 0.15
130
149.83
0.95 / 0.36
0.41 / 0.15
140
153.58
1 / 0.37
0.43 / 0.16
150
157.33
1.05 / 0.39
0.45 / 0.17
160
161.05
1.1 / 0.41
0.47 / 0.17
170
164.77
1.15 / 0.43
0.49 / 0.18
180
168.48
1.2 / 0.44
0.51 / 0.19
190
172.17
1.25 / 0.46
0.53 / 0.2
200
175.86
1.3 / 0.48
0.55 / 0.2
210
179.53
1.35 / 0.49
0.57 / 0.21
220
183.19
1.4 / 0.51
0.59 / 0.22
230
186.84
1.45 / 0.53
0.61 / 0.22
240
190.47
1.5 / 0.54
0.63 / 0.23
250
194.1
1.55 / 0.56
0.65 / 0.24
260
197.71
1.6 / 0.58
0.67 / 0.24
270
201.31
1.65 / 0.59
0.69 / 0.25
280
204.9
1.7 / 0.61
0.71 / 0.25
290
208.48
1.75 / 0.63
0.73 / 0.26
300
212.05
1.8 / 0.64
0.75 / 0.27
310
215.61
1.85 / 0.66
0.77 / 0.27
320
219.15
1.9 / 0.67
0.79 / 0.28
330
222.68
1.95 / 0.69
0.81 / 0.29
340
226.21
2 / 0.7
0.83 / 0.29
350
229.72
2.05 / 0.72
0.85 / 0.3
360
233.21
2.1 / 0.73
0.87 / 0.3
370
236.7
2.15 / 0.75
0.89 / 0.31
380
240.18
2.2 / 0.76
0.91 / 0.32
390
243.64
2.25 / 0.78
0.93 / 0.32
400
247.09
2.3 / 0.79
0.95 / 0.33
410
250.53
2.35 / 0.81
0.97 / 0.33
420
253.96
2.4 / 0.82
0.99 / 0.34
430
257.38
2.45 / 0.84
1.01 / 0.34
440
260.78
2.5 / 0.85
1.03 / 0.35
450
264.18
2.55 / 0.86
1.05 / 0.36
460
267.56
2.6 / 0.88
1.07 / 0.36
470
270.93
2.65 / 0.89
1.09 / 0.37
480
274.29
2.7 / 0.91
1.11 / 0.37
490
277.64
2.75 / 0.92
1.13 / 0.38
500
280.98
2.8 / 0.93
1.15 / 0.38
510
284.3
2.85 / 0.95
1.17 / 0.39
520
287.62
2.9 / 0.96
1.19 / 0.39
530
290.92
2.95 / 0.97
1.21 / 0.4
540
294.21
3 / 0.98
1.23 / 0.4
550
297.49
3.05 / 1
1.25 / 0.41

 

 

 

 

 

Pt1000 characteristic curve

 

Diagram Pt1000 characteristic curve

 

 

Resistance table Pt1000

Show/Hide Pt1000 table

 

Temperature
Resistance
Tolerance class B
Tolerance class A
°C
Ω
in ± °C / in ± Ω
in ± °C / in ± Ω
-40
842.47
0.5 / 1.99
0.23 / 0.91
-30
882.11
0.45 / 1.78
0.21 / 0.83
-20
921.57
0.4 / 1.57
0.19 / 0.75
-10
960.86
0.35 / 1.37
0.17 / 0.67
0
1000
0.3 / 1.17
0.15 / 0.59
10
1039.03
0.35 / 1.36
0.17 / 0.66
20
1077.94
0.4 / 1.55
0.19 / 0.74
30
1116.73
0.45 / 1.74
0.21 / 0.81
40
1155.41
0.5 / 1.93
0.23 / 0.89
50
1193.97
0.55 / 2.12
0.25 / 0.96
60
1232.42
0.6 / 2.3
0.27 / 1.04
70
1270.75
0.65 / 2.49
0.29 / 1.11
80
1308.97
0.7 / 2.67
0.31 / 1.18
90
1347.07
0.75 / 2.85
0.33 / 1.26
100
1385.06
0.8 / 3.03
0.35 / 1.33
110
1422.93
0.85 / 3.21
0.37 / 1.4
120
1460.68
0.9 / 3.39
0.39 / 1.47
130
1498.32
0.95 / 3.57
0.41 / 1.54
140
1535.84
1 / 3.75
0.43 / 1.61
150
1573.25
1.05 / 3.92
0.45 / 1.68
160
1610.54
1.1 / 4.1
0.47 / 1.75
170
1647.72
1.15 / 4.27
0.49 / 1.82
180
1684.78
1.2 / 4.44
0.51 / 1.89
190
1721.73
1.25 / 4.61
0.53 / 1.95
200
1758.56
1.3 / 4.78
0.55 / 2.02
210
1795.28
1.35 / 4.95
0.57 / 2.09
220
1831.88
1.4 / 5.11
0.59 / 2.16
230
1868.36
1.45 / 5.28
0.61 / 2.22
240
1904.73
1.5 / 5.45
0.63 / 2.29
250
1940.98
1.55 / 5.61
0.65 / 2.35
260
1977.12
1.6 / 5.77
0.67 / 2.42
270
2013.14
1.65 / 5.93
0.69 / 2.48
280
2049.05
1.7 / 6.09
0.71 / 2.54
290
2084.84
1.75 / 6.25
0.73 / 2.61
300
2120.52
1.8 / 6.41
0.75 / 2.67
310
2156.08
1.85 / 6.57
0.77 / 2.73
320
2191.52
1.9 / 6.72
0.79 / 2.8
330
2226.85
1.95 / 6.88
0.81 / 2.86
340
2262.06
2 / 7.03
0.83 / 2.92
350
2297.16
2.05 / 7.18
0.85 / 2.98
360
2332.14
2.1 / 7.33
0.87 / 3.04
370
2367.01
2.15 / 7.48
0.89 / 3.1
380
2401.76
2.2 / 7.63
0.91 / 3.16
390
2436.4
2.25 / 7.78
0.93 / 3.22
400
2470.92
2.3 / 7.92
0.95 / 3.27
410
2505.33
2.35 / 8.07
0.97 / 3.33
420
2539.62
2.4 / 8.21
0.99 / 3.39
430
2573.79
2.45 / 8.36
1.01 / 3.45
440
2607.85
2.5 / 8.5
1.03 / 3.5
450
2641.79
2.55 / 8.64
1.05 / 3.56
460
2675.62
2.6 / 8.78
1.07 / 3.61
470
2709.33
2.65 / 8.91
1.09 / 3.67
480
2742.93
2.7 / 9.05
1.11 / 3.72
490
2776.41
2.75 / 9.19
1.13 / 3.78
500
2809.78
2.8 / 9.32
1.15 / 3.83
510
2843.03
2.85 / 9.46
1.17 / 3.88
520
2876.16
2.9 / 9.59
1.19 / 3.94
530
2909.18
2.95 / 9.72
1.21 / 3.99
540
2942.08
3 / 9.85
1.23 / 4.04
550
2974.87
3.05 / 9.98
1.25 / 4.09

 

 

Which is more accurate? Pt100 or Pt1000?

The platinum resistors Pt100 and Pt1000 are offered in both tolerance class A and tolerance class B. This raises the question of which temperature sensor is more accurate. Tolerance class A is more accurate than tolerance class B. However, a Pt100 measuring resistor boasts similar measuring accuracy to a Pt1000 sensor of the same tolerance class. Nonetheless, both temperature sensors have different susceptibility to measuring errors, which is discussed in the following sections.

Influence of conductor resistance on accuracy

The temperature measurement with Pt100/Pt1000 is achieved through a change in electrical resistance. Other electrical resistances, such as the resistivity of connecting cables, have a negative impact on the measuring accuracy of the temperature measurement. The resistance depends on the material (usually copper), the length and the cross-section of the cable. The order of magnitude of the measuring error is shown using the example of a 50 m cable with 2-wire measurement.

If a Pt100 sensor is connected to the electronic measuring equipment via a 50 m cable, the actual measured resistance is 5.25 Ohm higher due to the conductor resistance, which obviously affects the temperature measurement. Each ohm of resistivity results in a measuring error of approx. 2.5 Kelvin. This results in a measuring error of approx. 13 °C. The resistance of a Pt1000 resistor is ten times greater than that of a Pt100 sensor, meaning the influence of the electrical conductor is ten times smaller. As explained in the example, the measuring error can be calculated and deducted from the actual measurement result. Alternatively, another measuring circuit can be used to compensate for the error.
Rule of thumb: “Each ohm of resistivity results in a measuring error of approx. 2.5 Kelvin.”

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