Pt500 | GUILCOR SENSORS

Pt500
Temperature sensors

Pt500 temperature sensors deliver higher resistance values, enhancing measurement resolution and reducing sensitivity to line resistance.

Maximum precision
+/- 0.1°K

Minimum temperature
-200°C

Maximum temperature
+600°C

Minimum dimensions
2 x 8 x 30

Response time
Medium

Self-heating
Low

Price
Medium

Drift
Low

What is a Pt500 sensor ?

The Pt500 is a platinum resistance sensor that presents 500 Ω at 0 °C.

It offers increased sensitivity compared to the Pt100, with a higher output voltage and excellent linearity.

This sensor is ideal for digital measurement applications (controllers, HVAC regulators, process probes) requiring good accuracy without excessive amplification.

Operating principle

Like all platinum RTD sensors, the Pt500 follows the Callendar–Van Dusen equation:

R(T) = R_0 [1 + A·T + B·T^2 + C·(T - 100)·T^3]

with :

R_0 = 500 Ω
A = 3,9083 × 10⁻³
B = -5,775 × 10⁻⁷
C = −4,183×10−12 (pour T < 0 °C)

The output tension being about 5 times higher than that of a Pt100, the Pt500 is perfectly suited for the 0–5 V or 0–10 V analog inputs of industrial systems.

Technical specifications

Parameter	Typical Value
Nominal resistance at 0 °C	500 Ω
Temperature coefficient (α)	0,00385 °C⁻¹
Measurement range	−200 °C to +600 °C
Linearity	Excellent
Element material	Platinium pur
Typical measuring current	0,2 à 0,5 mA
Response time	0,5 s
Long-term drift	< 0,05 °C/year

Wiring configuration

Type	Description	Precision
2-wire	Simple but not very accurate over long distances.	⚠️ Average
3-wire	Partially compensates for the resistance of the cables.	✅ Good
4-wire	Completely eliminates parasitic resistance.	🏆 Excellent

Self-heating

The Pt500 operates with a low excitation current (0.2 to 0.5 mA).

Due to its high resistance, the internal heating remains below 0.02 °C, even in still air.

Application areas

🌡️ HVAC Controllers and Regulators

⚙️ Industrial Instrumentation Systems

🧪 Electronic Test Benches

🚗 Embedded Measurements and Energy Monitoring

🔬 Automated Scientific Equipment

Should I choose a Pt500 sensor ?

Strengths points

📈 High measurement sensitivity
→ Thanks to its 500 Ω at 0 °C, the Pt500 delivers a stronger and more usable signal without the need for complex amplification.
⚙️ Easy integration into digital systems
→ Compatible with standard analog inputs (0-5 V / 0-10 V), it easily integrates with controllers, regulators, and ADC boards.
🧊 Excellent stability/cost ratio
→ It maintains the linearity and stability of platinum while being more economical than a Pt1000 or Pt5000.

Weaknesses points

💰 Slightly more expensive than a Pt100
→ The higher quantity of platinum modestly increases the unit cost.
🔌 Requires appropriate excitation
→ A current that is too strong (> 0.5 mA) can distort the measurement; the current source must be adjusted precisely.
🌡️ Response time a bit slower
→ Its higher resistance implies a slight thermal inertia, noticeable during rapid temperature changes.

Useful information

Here is some useful information regarding Pt500 sensors.

Table ohmic values

°C	0	1	2	3	4	5	6	7	8	9
0	500,00	501,95	503,91	505,86	507,81	509,76	511,71	513,66	515,61	517,56
10	519,51	521,46	523,41	525,36	527,30	529,25	531,19	533,14	535,08	537,02
20	538,97	540,91	542,85	544,79	546,73	548,67	550,61	552,55	554,49	556,43
30	558,36	560,30	562,24	564,17	566,11	568,04	569,98	571,91	573,84	575,77
40	577,70	579,63	581,56	583,49	585,42	587,35	589,28	591,21	593,13	595,06
50	596,99	598,91	600,84	602,76	604,68	606,60	608,53	610,45	612,37	614,29
60	616,21	618,13	620,05	621,97	623,88	625,80	627,72	629,63	631,55	633,46
70	635,38	637,29	639,20	641,11	643,03	644,94	646,85	648,76	650,67	652,58
80	654,48	656,39	658,30	660,21	662,11	664,02	665,92	667,83	669,73	671,63
90	673,53	675,44	677,34	679,24	681,14	683,04	684,94	686,84	688,73	690,63
100	692,53	694,42	696,32	698,21	700,11	702,00	703,90	705,79	707,68	709,57
110	711,46	713,35	715,24	717,13	719,02	720,91	722,80	724,68	726,57	728,45
120	730,34	732,22	734,11	735,99	737,87	739,76	741,64	743,52	745,40	747,28
130	749,16	751,04	752,92	754,79	756,67	758,55	760,42	762,30	764,17	766,05
140	767,92	769,79	771,67	773,54	775,41	777,28	779,15	781,02	782,89	784,76
150	786,63	788,49	790,36	792,23	794,09	795,96	797,82	799,68	801,55	803,41
160	805,27	807,13	808,99	810,85	812,71	814,57	816,43	818,29	820,15	822,00
170	823,86	825,72	827,57	829,43	831,28	833,13	834,99	836,84	838,69	840,54
180	842,39	844,24	846,09	847,94	849,79	851,64	853,48	855,33	857,17	859,02
190	860,86	862,71	864,55	866,40	868,24	870,08	871,92	873,76	875,60	877,44
200	879,28	881,12	882,96	884,79	886,63	888,47	890,30	892,14	893,97	895,80
210	897,64	899,47	901,30	903,13	904,96	906,79	908,62	910,45	912,28	914,11
220	915,94	917,76	919,59	921,42	923,24	925,07	926,89	928,71	930,54	932,36
230	934,18	936,00	937,82	939,64	941,46	943,28	945,10	946,91	948,73	950,55
240	952,36	954,18	955,99	957,81	959,62	961,43	963,25	965,06	966,87	968,68
250	970,49	972,30	974,11	975,92	977,73	979,53	981,34	983,14	984,95	986,76
260	988,56	990,36	992,17	993,97	995,77	997,57	999,37	1001,17	1002,97	1004,77
270	1006,57	1008,37	1010,17	1011,96	1013,76	1015,55	1017,35	1019,14	1020,94	1022,73
280	1024,52	1026,32	1028,11	1029,90	1031,69	1033,48	1035,27	1037,06	1038,85	1040,63
290	1042,42	1044,21	1045,99	1047,78	1049,56	1051,35	1053,13	1054,91	1056,69	1058,48
300	1060,26	1062,04	1063,82	1065,60	1067,38	1069,15	1070,93	1072,71	1074,49	1076,26
310	1078,04	1079,81	1081,59	1083,36	1085,13	1086,91	1088,68	1090,45	1092,22	1093,99
320	1095,76	1097,53	1099,30	1101,07	1102,83	1104,60	1106,37	1108,13	1109,90	1111,66
330	1113,42	1115,19	1116,95	1118,71	1120,47	1122,24	1124,00	1125,76	1127,51	1129,27
340	1131,03	1132,79	1134,55	1136,30	1138,06	1139,81	1141,57	1143,32	1145,08	1146,83
350	1148,58	1150,33	1152,08	1153,83	1155,58	1157,33	1159,08	1160,83	1162,58	1164,33
360	1166,07	1167,82	1169,56	1171,31	1173,05	1174,80	1176,54	1178,28	1180,02	1181,76
370	1183,51	1185,25	1186,99	1188,72	1190,46	1192,20	1193,94	1195,67	1197,41	1199,15
380	1200,88	1202,62	1204,35	1206,08	1207,82	1209,55	1211,28	1213,01	1214,74	1216,47
390	1218,20	1219,93	1221,66	1223,38	1225,11	1226,84	1228,56	1230,29	1232,01	1233,74
400	1235,46	1237,18	1238,91	1240,63	1242,35	1244,07	1245,79	1247,51	1249,23	1250,95

Precision class table

Temperature (°C)	Classe A (°K)	Classe B (°K)	Classe 1/3 B (°K)	Classe 1/10 B (°K)
-200	0,55	1,3	0,43	0,13
-190	0,53	1,25	0,42	0,12
-180	0,51	1,2	0,4	0,12
-170	0,49	1,15	0,38	0,12
-160	0,47	1,1	0,37	0,11
-150	0,45	1,05	0,35	0,11
-140	0,43	1	0,33	0,1
-130	0,41	0,95	0,32	0,1
-120	0,39	0,9	0,3	0,09
-110	0,37	0,85	0,28	0,08
-100	0,35	0,8	0,27	0,08
-90	0,33	0,75	0,25	0,08
-80	0,31	0,7	0,23	0,07
-70	0,29	0,65	0,22	0,06
-60	0,27	0,6	0,2	0,06
-50	0,25	0,55	0,18	0,06
-40	0,23	0,5	0,17	0,05
-30	0,21	0,45	0,15	0,04
-20	0,19	0,4	0,13	0,04
-10	0,17	0,35	0,12	0,03
0	0,15	0,3	0,1	0,03
10	0,17	0,35	0,12	0,03
20	0,19	0,4	0,13	0,04
30	0,21	0,45	0,15	0,04
40	0,23	0,5	0,17	0,05
50	0,25	0,55	0,18	0,06
60	0,27	0,6	0,2	0,06
70	0,29	0,65	0,22	0,06
80	0,31	0,7	0,23	0,07
90	0,33	0,75	0,25	0,08
100	0,35	0,8	0,27	0,08
110	0,37	0,85	0,28	0,08
120	0,39	0,9	0,3	0,09
130	0,41	0,95	0,32	0,1
140	0,43	1	0,33	0,1
150	0,45	1,05	0,35	0,11
160	0,47	1,1	0,37	0,11
170	0,49	1,15	0,38	0,12
180	0,51	1,2	0,4	0,12
190	0,53	1,25	0,42	0,12
200	0,55	1,3	0,43	0,13

Example of application of the linearization equation of a PT500

The Pt500 sensor follows the same Callendar–Van Dusen equation as other platinum RTDs:

R(T) = R₀ [1 + A·T + B·T² + C·(T − 100)·T³]

with :

R₀ = 500 Ω
A = 3,9083 × 10⁻³
B = −5,775 × 10⁻⁷
C = −4,183 × 10⁻¹² (pour T < 0 °C)

This relationship ensures great linearity and remarkable stability from -200 °C to +600 °C.

🔹 Example 1: calculation of resistance at 100 °C

R(100) = 500 × [1 + 3,9083 × 10⁻³ × 100 − 5,775 × 10⁻⁷ × 100²]

R(100) = 500 × (1 + 0,39083 − 0,005775)

R(100) = 500 × 1,385055 = 692,53 Ω

✅ Result: at 100 °C, the resistance of a Pt500 is approximately 692.5 Ω.

🔹 Example 2: calculating the temperature from a measured resistance

We measure R = 570.6Ω.

What is the corresponding temperature?

T = (−A + √(A² − 4B(1 − R/R₀))) / (2B)

T = (−3,9083 × 10⁻³ + √[(3,9083 × 10⁻³)² − 4 × (−5,775 × 10⁻⁷) × (1 − 570,6 / 500)]) / [2 × (−5,775 × 10⁻⁷)]

T ≈ 34 °C

✅ Result: the corresponding temperature is approximately 34 °C.

🔹 Practical notes

The equation is directly supported by most industrial controllers.
On microcontrollers, it can be integrated via a polynomial formula or an R/T table.
The Pt500 offers increased resolution due to its resistance being five times greater than that of a Pt100.

Integration diagram in an electronic system

The nominal resistance of 500 Ω provides a comfortable output voltage and good noise immunity, allowing for the use of a low excitation current (0.2–0.5 mA).

🔹 Typical components of the assembly

Component	Function
RTD Pt500 (3 or 4 wires)	Sensitive platinum element
Stable current source (~0.3 mA)	Probe power supply
Instrumentation amplifier (INA333, AD8426)	Amplify the tension from the RTD
High-resolution ADC (≥ 16 bits)	Convert the voltage into digital data
Microcontroller (STM32, ESP32, Arduino)	Calculate T = f(R) and apply the compensation
RC filtering / shielded cable	Noise reduction and signal stabilization

🔹 Functional diagram (ASCII)

              +3.3 V / +5 V
                   │
       Current source (0.3 mA)
                   │
                [ Pt500 ]
       (2 power wires + 2 measurement wires)
           │                    │
           │                    │
   Diff. amplifier ──→ High-resolution ADC
                               │
                        [ Microcontroller ]
                   (Calculation T = f(R) + display)

🔹 Operating Principle

1️⃣ A constant current flows through the RTD.

→ At 0 °C: V = 500 Ω × 0.3 mA = 150 mV

→ At 100 °C: V ≈ 692 Ω × 0.3 mA = 208 mV

2️⃣ The amplifier boosts this signal (gain ≈ 20–50) to obtain an amplitude suitable for the ADC (0–5 V).

3️⃣ The microcontroller calculates the temperature using the Callendar–Van Dusen equation.

🔹 Best Practices