Ni120 | GUILCOR SENSORS

Ni120
Temperature sensors

Ni120 temperature sensors provide enhanced sensitivity compared to Ni100, commonly used in HVAC and control applications.

Maximum precision
+/- 0.15°K

Minimum temperature
-60°C

Maximum temperature
+180°C

Minimum dimensions
1,5 x 5 x 15

Response time
Fast

Self-heating
Low

Price
Medium

Drift
Low

What is a Ni120 sensor ?

The Ni120 is a pure nickel resistance probe with a nominal resistance of 120 Ω at 0 °C.

It is a variant of the Ni100, providing a slightly higher signal for the same excitation, and better stability over long measurement lines.

Widely used in HVAC temperature control systems, test benches, and embedded electronic equipment, it combines sensitivity, response speed, and controlled cost.

Operating principle

The operation is based on the variation of the resistance of pure nickel according to temperature:

R(T) = R₀ (1 + αT + βT²)

avec :

R₀ = 120 Ω
α = 6,18 × 10⁻³
β = 1,4 × 10⁻⁵

This equation is quasi-linear between -60 °C and +180 °C, ensuring good accuracy without complex correction.

Technical specifications

Parameter	Typical Value
Nominal resistance at 0 °C	120 Ω
Temperature coefficient (α)	0,00618 °C⁻¹
Measurement range	−60 °C to +180 °C
Linearity	Very good
Element material	Pure nickel
Typical measuring current	0,1 to 0,3 mA
Response time	0,3 s
Long-term drift	< 0,1 °C/year

Wiring configuration

Type	Description	Precision
2-wire	Simple, sufficient for short applications.	✅ Good
3-wire	Compensate for the cable's resistance.	🏆 Excellent
4-wire	Rarely necessary.	💡 Very precise

Self-heating

Thanks to its superior resistance, the Ni120 requires a lower current to achieve the same voltage as a Ni100.

Self-heating remains below 0.03 °C, even in stagnant environments.

Application areas

🌡️ HVAC and thermal automation

⚙️ Medium precision industrial instrumentation

🚗 Automotive embedded control

🧪 Test benches and electronic monitoring

🧰 Economical measuring devices

Should I choose a Ni120 sensor ?

Strengths points

⚡ Signal stronger than the Ni100
→ With 120 Ω at 0 °C, the Ni120 generates a higher output voltage, which improves measurement resolution and reduces noise without the need for an amplifier.
🧠 Natural linearity
→ The R/T curve is nearly linear over the range of -60 °C to +180 °C, simplifying calculations and integration into measurement systems.
💶 Economic and precise solution
→ It is an excellent compromise between cost and performance, ideal for HVAC, automotive, or industrial systems with a controlled budget.

Weaknesses points

🌡️ Not suitable for extreme temperatures
→ The limited operating temperature range (−60 °C to +180 °C) makes it incompatible with cryogenic or high-temperature environments.
🧪 Sensitive to oxidation
→ Nickel degrades faster than platinum at high temperatures, reducing long-term stability.
📏 Less standardized than the Pt100
→ Not all regulators recognize the Ni120 without specific configuration, which can complicate integration.

Useful information

Here is some useful information regarding the Ni120 sensors.

Table of ohmic values

Temp (°C)	0	1	2	3	4	5	6	7	8	9
0	120.00	120.74	121.48	122.23	122.97	123.71	124.46	125.20	125.95	126.69
10	127.44	128.18	128.93	129.67	130.42	131.16	131.91	132.65	133.40	134.14
20	134.89	135.63	136.38	137.12	137.87	138.61	139.36	140.10	140.85	141.59
30	142.34	143.08	143.83	144.57	145.32	146.06	146.81	147.55	148.30	149.04
40	149.79	150.53	151.28	152.02	152.77	153.51	154.26	155.00	155.75	156.49
50	157.24	157.98	158.73	159.47	160.22	160.96	161.71	162.45	163.20	163.94
60	164.69	165.43	166.18	166.92	167.67	168.41	169.16	169.90	170.65	171.39
70	172.14	172.88	173.63	174.37	175.12	175.86	176.61	177.35	178.10	178.84
80	179.59	180.33	181.08	181.82	182.57	183.31	184.06	184.80	185.55	186.29
90	187.04	187.78	188.53	189.27	190.02	190.76	191.51	192.25	193.00	193.74
100	194.49	195.23	195.98	196.72	197.47	198.21	198.96	199.70	200.45	201.19
110	201.94	202.68	203.43	204.17	204.92	205.66	206.41	207.15	207.90	208.64
120	209.39	210.13	210.88	211.62	212.37	213.11	213.86	214.60	215.35	216.09
130	216.84	217.58	218.33	219.07	219.82	220.56	221.31	222.05	222.80	223.54
140	224.29	225.03	225.78	226.52	227.27	228.01	228.76	229.50	230.25	230.99
150	231.74	232.48	233.23	233.97	234.72	235.46	236.21	236.95	237.70	238.44
160	239.19	239.93	240.68	241.42	242.17	242.91	243.66	244.40	245.15	245.89
170	246.64	247.38	248.13	248.87	249.62	250.36	251.11	251.85	252.60	253.34
180	254.09	254.83	255.58	256.32	257.07	257.81	258.56	259.30	260.05	260.79

Precision class table

Temperature (°C)	Class B (±°C)	Class A (±°C)	1/3 B (DIN) (±°C)	1/10 B (DIN) (±°C)
−60	0.60	0.27	0.20	0.06
−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	0.28	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 of the linearization equation of a Ni120

The Ni120 follows a quadratic law between temperature and resistance, characteristic of nickel sensors:

R(T) = R₀ (1 + αT + βT²)

avec :

R₀ = 120 Ω
α = 6,18 × 10⁻³
β = 1,4 × 10⁻⁵
(valable entre −60 °C et +180 °C)

This simple equation allows for a direct conversion between the measured resistance and the temperature without complex correction.

🔹 Example 1: calculating the resistance at 100 °C

R(100) = 120 × [1 + 6,18 × 10⁻³ × 100 + 1,4 × 10⁻⁵ × 100²]

R(100) = 120 × (1 + 0,618 + 0,14) = 120 × 1,758 = 210,96 Ω

✅ Result: at 100 °C, the resistance of Ni120 is approximately 211 Ω.

🔹 Example 2: calculating the temperature from a measured resistance

We measure R=165Ω.

What is the corresponding temperature ?

βT² + αT + (1 − R/R₀) = 0

1,4 × 10⁻⁵ T² + 6,18 × 10⁻³ T + (1 − 165 / 100) = 0

1,4 × 10⁻⁵ T² + 6,18 × 10⁻³ T − 0,375 = 0

T = [−6,18 × 10⁻³ + √((6,18 × 10⁻³)² − 4 × 1,4 × 10⁻⁵ × (−0,375))] / (2 × 1,4 × 10⁻⁵)

T ≈ 57 °C

✅ Result: the equivalent temperature is approximately 57 °C.

🔹 Practical notes

The Ni120 equation is easy to implement on microcontrollers (Arduino, STM32, ESP32).
The stronger signal compared to the Ni100 improves resolution without increasing current.
Outside the range of −60 °C → +180 °C, non-linearity increases significantly, so it should be avoided.

Integration diagram in an electronic system

The Ni120 is ideal for low-cost setups where the linearity of nickel is sufficient, while providing a signal that can be directly used by an analog-to-digital converter (ADC).

🔹 Typical assembly components

Composant	Function
RTD Ni120 (2 or 3 wires)	Pure nickel sensitive element
Stable current source (~0.2 mA)	Feed the probe
Differential amplifier (INA333, AD620)	Amplify the signal
ADC 12 to 16 bits	Convert the voltage to a numerical value
Microcontroller (STM32, ESP32, Arduino)	Calculate T = f(R)
RC filtering / shielded wiring	Reduces EMI interference

🔹 Functional diagram (ASCII)

              +3.3 V / +5 V
                   │
       Current source (0.2 mA)
                   │
                [ Ni120 ]
       (2 power wires + 1 measurement wire)
           │                  │
           │                  │
  Diff. amplifier ───→ ADC 16 bits
                              │
                      [ Microcontroller ]
                 (Calculation T = f(R) + display)

🔹 Operating Principle

1️⃣ A constant current flows through the RTD.

→ At 0 °C: V = 120 Ω × 0.2 mA = 24 mV

→ At 100 °C: V ≈ 211 Ω × 0.2 mA = 42 mV

2️⃣ The amplifier raises the voltage (gain ≈ 50 → output ≈ 2 V).

3️⃣ The microcontroller calculates the temperature from the resistance using the quadratic equation.

🔹 Best Practices

🧩 Use a 3-wire configuration to reduce line errors.

⚙️ Limit the current to ≤ 0.3 mA to avoid self-heating.

💧 Protect the probe in a stainless steel or ceramic housing if humidity is present.

🔄 Calibrate regularly at 0 °C and 100 °C.

🧲 Use an RC filter (1 kΩ / 100 nF) to stabilize the signal.