Cu10 | GUILCOR SENSORS

Cu10
Temperature sensors

Cu10 temperature sensors are copper RTDs offering linear response and high accuracy at low temperature ranges.

Maximum precision
+/- 0.20°K

Minimum temperature
-50°C

Maximum temperature
+180°C

Minimum dimensions
1,5 x 5 x 15

Response time
Fast

Self-heating
Low

Price
High

Drift
Medium

What is a Cu10 sensor ?

The Cu10 is a pure copper resistance probe, with a nominal resistance of 10 Ω at 0 °C.

It is primarily used for applications requiring good linearity and minimal cost, such as HVAC systems, basic thermal regulation, and consumer devices.

Although less stable than platinum, it remains very accurate in the limited range of −50 to +180 °C.

Operating principle

Copper has a resistivity that increases linearly with temperature, according to the relationship:

R(T) = R₀ (1 + αT)

avec :

R₀ = 10 Ω
α = 4,28 × 10⁻³

This almost perfect linearity over the useful range makes it an excellent choice for direct temperature measurements, without the need for complex calculations.

Technical specifications

Parameter	Typical Value
Nominal resistance at 0 °C	10 Ω
Temperature coefficient (α)	0,00428 °C⁻¹
Measurement range	−50 °C to +180 °C
Linearity	Excellent
Element material	Pure copper
Typical measuring current	1 → 3 mA
Response time	0,3 s
Long-term drift	< 0,1 °C/year

Wiring configuration

Type	Description	Precision
2-wire	Sufficient for short edits.	✅ Good
3-wire	Compensate for the resistance of the cables.	🏆 Very good
4-wire	Reserved for calibrations.	💡 Excellent

Self-heating

The Cu10 is powered with a stronger current than platinum or nickel RTDs, but its very low resistance limits internal heating to < 0.05 °C.

Application areas

🏢 HVAC Systems (heating, ventilation, air conditioning)

⚙️ Controllers and surface probes

💧 Temperature control in hydraulic circuits

🚗 Low-cost embedded devices

🔧 Household appliances and home electronics

Should I choose a Cu10 sensor ?

Strengths points

📈 Quasi-perfect linearity
→ Copper has a practically linear R/T relationship, which facilitates direct measurements without the need for software compensation.
💰 Ultra-economical solution
→ The Cu10 is one of the least expensive RTD sensors, perfect for large series or applications where absolute precision is not critical.
⚡ Quick response
→ Due to its low mass and high thermal conductivity, Cu10 reacts very quickly to temperature changes.

Weaknesses points

🌡️ Limited use beach
→ The Cu10 does not exceed +180 °C, making it unsuitable for high-temperature industrial environments.
🧪 Oxidation sensitivity
→ Copper naturally oxidizes in open air, leading to a drift in resistance if it is not protected.
📏 Lack of standardization
→ Unlike the Pt100, the Cu10 is not standardized internationally, which limits compatibility with temperature converters.

Useful information

Here is some useful information regarding the Cu10 sensors.

Table of ohmic values

°C	0	1	2	3	4	5	6	7	8	9
-50	7.87	7.91	7.95	7.99	8.04	8.08	8.12	8.16	8.21	8.25
-40	8.29	8.33	8.38	8.42	8.46	8.51	8.55	8.59	8.63	8.68
-30	8.72	8.76	8.80	8.85	8.89	8.93	8.98	9.02	9.06	9.10
-20	9.15	9.19	9.23	9.27	9.32	9.36	9.40	9.45	9.49	9.53
-10	9.57	9.62	9.66	9.70	9.75	9.79	9.83	9.88	9.92	9.96
0	10.00	10.04	10.09	10.13	10.17	10.22	10.26	10.30	10.35	10.39
10	10.43	10.47	10.52	10.56	10.60	10.65	10.69	10.73	10.78	10.82
20	10.85	10.90	10.94	10.98	11.03	11.07	11.11	11.16	11.20	11.24
30	11.28	11.33	11.37	11.41	11.46	11.50	11.54	11.59	11.63	11.67
40	11.71	11.75	11.80	11.84	11.88	11.93	11.97	12.01	12.06	12.10
50	12.13	12.18	12.22	12.26	12.31	12.35	12.39	12.44	12.48	12.52
60	12.56	12.61	12.65	12.69	12.74	12.78	12.82	12.87	12.91	12.95
70	12.99	13.03	13.08	13.12	13.16	13.21	13.25	13.29	13.34	13.38
80	13.42	13.46	13.51	13.55	13.59	13.64	13.68	13.72	13.77	13.81
90	13.84	13.89	13.93	13.97	14.02	14.06	14.10	14.15	14.19	14.23
100	14.27	14.32	14.36	14.40	14.45	14.49	14.53	14.58	14.62	14.66
110	14.70	14.75	14.79	14.83	14.88	14.92	14.96	15.01	15.05	15.09
120	15.13	15.18	15.22	15.26	15.31	15.35	15.39	15.44	15.48	15.52
130	15.55	15.60	15.64	15.68	15.73	15.77	15.81	15.86	15.90	15.94
140	15.98	16.03	16.07	16.11	16.16	16.20	16.24	16.29	16.33	16.37
150	16.41	16.46	16.50	16.54	16.59	16.63	16.67	16.72	16.76	16.80
160	16.84	16.89	16.93	16.97	17.02	17.06	17.10	17.15	17.19	17.23
170	17.26	17.31	17.35	17.39	17.44	17.48	17.52	17.57	17.61	17.65
180	17.69

Precision class table

Temperature (°C)	Class B (±°C)	Class A (±°C)	1/3 B (±°C)	1/10 B (±°C)
-50	0.55	0.25	0.18	0.06
-40	0.50	0.23	0.17	0.05
-30	0.45	0.21	0.15	0.04
-20	0.40	0.19	0.13	0.04
-10	0.35	0.17	0.12	0.04
0	0.30	0.15	0.10	0.03
10	0.35	0.17	0.12	0.04
20	0.40	0.19	0.13	0.04
30	0.45	0.21	0.15	0.05
40	0.50	0.23	0.17	0.05
50	0.55	0.25	0.18	0.06
60	0.60	0.27	0.20	0.06
70	0.65	0.29	0.22	0.07
80	0.70	0.31	0.23	0.07
90	0.75	0.33	0.25	0.08
100	0.80	0.35	0.27	0.08
110	0.85	0.37	0.29	0.09
120	0.90	0.39	0.30	0.09
130	0.95	0.41	0.32	0.10
140	1.00	0.43	0.33	0.10
150	1.05	0.45	0.35	0.11
160	1.10	0.47	0.37	0.11
170	1.15	0.49	0.38	0.12
180	1.20	0.51	0.40	0.12

Example of application the linearization equation of a Cu10

The Cu10 is one of the few RTD sensors whose relationship between resistance and temperature is almost perfectly linear.

Therefore, a simplified equation is used :

R(T) = R₀ (1 + αT)

avec :

R₀ = 10 Ω
α = 4,28 × 10⁻³
(valable de −50 °C à +180 °C)

🔹 Example 1: calculation of resistance at 100 °C

R(100) = 10 × [1 + 4,28 × 10⁻³ × 100]

R(100) = 10 × (1 + 0,428) = 10 × 1,428 = 14,28 Ω

✅ Result: at 100 °C, the resistance of Cu10 is approximately 14.28 Ω.

🔹 Example 2: calculating the temperature from a measured resistance

We measure R=12.85Ω.

What is the corresponding temperature?

T = (R / R₀ − 1) / α

T = (12,85 / 10 − 1) / (4,28 × 10⁻³)

T = 0,285 / 0,00428 = 66,6 °C

✅ Result: the equivalent temperature is approximately 67 °C.

🔹 Practical Remarks

The Cu10 equation is linear, making it ideal for simple analog reading.
It can be used directly on a Wheatstone bridge or a microcontroller without complex conversion.
Copper reacts quickly, but care must be taken to prevent oxidation: always encapsulate the probe (glass, Teflon, or stainless steel).

Integration diagram in an electronic system

The Cu10, with low resistance (10 Ω at 0 °C), requires a high-gain instrumentation amplifier to properly utilize the measured voltage.

The power supply should be from a stable current source to ensure the linearity of the signal.

🔹 Typical components of the setup

Composant	Function
RTD Cu10 (4 wires)	Temperature-sensitive element
Stable current source (~0.3 mA)	Create a tension proportional to the resistance
Instrumentation amplifier (e.g., INA333, AD8421)	Amplify the weak signal without noise interference
ADC Converter (16 to 24 bits)	Digitize the amplified tension
Microcontroller (STM32, Arduino, ESP32, etc.)	Convert the voltage to temperature
Shielded wiring (4 wires)	Reduces interference and parasitic resistance

🔹 Functional diagram (ASCII)

          +3.3 V / +5 V
               │
     Stable current source (0.3 mA)
               │
           [ Cu10 ]
     (2 power wires + 2 measurement wires)
         │             │
         │             │
 Instrumentation amplifier ───────→ High-resolution ADC
             				  │
                              │
                      [ Microcontroller ]
                      (calculate T = f(R))

🔹 Detailed Operating Principle

The current source applies about 0.3 mA in the Cu10.

→ At 0 °C: V = R×I = 10Ω × 0.3mA = 3mV

→ At 100 °C: V ≈ 4.28mV

The instrumentation amplifier increases this signal (typical gain 100 to 500).

→ A output voltage between 0.3 V and 2 V is obtained, suitable for a 3.3 V ADC.

The microcontroller calculates the temperature using the inverse equation:

T = R/R0−1 / α

The result is then:

displayed (screen, serial interface, Modbus bus, etc.),

or transmitted to a PLC or PID controller for process control.

🔹 Best Practices