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 1MΩ 
 Temperature sensors 

Maximum sensitivity NTC thermistor for ultra-low current applications and high-precision temperature measurement.

 Maximum precision
+/- 0,2°K

 Minimum temperature
-50°C

 Maximum temperature
+150°C

 Minimum dimensions
2 x 10

Response time

Medium

 Drift

Low

 Self-warming
Low

Price
Low

What is a NTC 1MΩ sensor ?Operating principleTechnical SpecificationsWiring ConfigurationSelf-warmingApplication areas

What is a NTC 1MΩ sensor ?

The NTC 1 MΩ is a very high impedance thermistor that offers almost zero power consumption.

Its use is intended for autonomous measurement systems where even the slightest dissipation matters — for example, in long-term environmental sensors, IoT modules, or passive precision instruments.

Operating principle

Its resistance follows the typical exponential law of NTC:

R(T) = R₂₅ × e^{β (1/T - 1/T₂₅)}

where :

  • R₂₅ = 1 000 000 Ω 
  • β ≈ 3950 K
  • T in kelvins

The reading is done via numerical linearization (Steinhart–Hart equation) to ensure accuracy.

Technical specifications

Parameter Typical value

Nominal resistance (25 °C)

 1 000 000 Ω ±1 %
Constant β 3950 K

Sensitive material

Metallic oxide (Mn, Ni, Co)

Type of case Epoxy / glass

Maximum measurement current

0,005 mA

Response time

0.3 to 1 s

Linearity

Exponential (non-linear)

Operating temperature

−50 → +150 °C

Lifetime

100,000 thermal cycles

Wiring Configuration

The NTC 1 MΩ is configured as a voltage divider, connected to a high-impedance analog input (≥10 MΩ).

It is often used with 24-bit ADC converters to detect minute variations.

 +Vcc
   │
  [Rfixe]
   │────► ADC (µC)
  [NTC 1MΩ]
   │
  GND

Self-warming

With a measurement current of less than 5 µA, the dissipation is negligible: no alteration of the actual measured temperature.

Application areas

🔋 Ultra-low power autonomous sensors (IoT, BLE, LoRa)

🌡️ Ambient and isolated object thermal monitoring

🩺 Sensitive medical instrumentation

🧠 Long-term measurement systems without recalibration

⚙️ Passive and calibrated electronic equipment


Should I choose a 1MΩ sensor ?

Strengths points

  • 🔋 Measurement current almost nonexistent
         → The NTC 1 MΩ consumes less than 5 µA: perfect for battery-powered devices or maintenance-free passive sensors.
  • 🧠 Ideal for high impedance differential measurements→ Used in instrumentation amplifiers or high Z inputs, it ensures exceptional electrical isolation.
  • 🌍 Compatible with isolated environments
         → Its very high resistance allows for reliable measurements even in areas with strong electromagnetic noise or with long transmission cables.
1MΩ Sensors

Weaknesses points

  • 🐢 Slow response in rapid variation
         → The very low measurement current induces a longer stabilization delay, which is not well suited for sudden temperature changes.
  • 🧮 Demanding lecture on the electronics side
         → Requires a 24-bit ADC or an input >10 MΩ to avoid charge errors and ensure accuracy.
  • 🌡️ Limited dynamic usage range
         → High temperatures (>120 °C) lead to a significant decrease in sensitivity, which limits its use to ambient applications.

Useful information

Here is some useful information regarding the 1MΩ sensors.

(NTC 1 MΩ at 25 °C, constant β = 3950 K)

Temperature (°C) Resistance (Ω) Temperature (°C) Resistance (Ω)
−50 24 940 000 60 292 000
−40 15 800 000 70 220 000
−30 10 170 000 80 169 000
−20 6 708 000 90 130 000
−10 4 484 000 100 101 000
0 3 046 000 110 78 000
10 2 095 000 120 63 000
20 1 474 000 130 50 000
25 1 000 000 140 40 000
30 686 000 150 32 000
40 476 000 160 26 000
50 336 000 170 21 000

💡 Between 0 °C and 100 °C, the resistance is divided by about 30 — typical of an NTC β ≈ 3950 K.

Class / Tolerance
 Tolerance at 25 °C (R25)
 Max error on T° (−40 → +125 °C)
 Typical usage
±1 % ±10 000 Ω ±0,2 K Precision thermal studies
±2 % ±20 000 Ω ±0,4 K Calibration Systems
±3 % ±30 000 Ω ±0,6 K Environmental monitoring
±5 % ±50 000 Ω ±1 K Long battery life devices / IoT
🔹 Glass or ceramic encapsulated versions are preferred for their excellent moisture stability and mechanical resistance.

Complete equation:

1/T = A + B · ln(R) + C · [ln(R)]³

Typical coefficients for NTC 1MΩ (β = 3950 K):

  • A = 1.4051 × 10⁻³
  • B = 2.369 × 10⁻⁴
  • C = 1.019 × 10⁻⁷


🔹 Example 1: Temperature from R

R = 686,000 Ω

ln(686000) = 13,44

1/T = 1,4051e−3 + 2,369e−4 (13,44) + 1,019e−7 (13,44)³ = 3,05e−3

T = 1 / 3,05e−3 = 328 K = 55 °C

✅ Measured temperature ≈ 55 °C


🔹 Example 2: Resistance from T

T = 80 °C = 353.15 K

R = R₂₅ · e^(β(1/T − 1/T₂₅))

R = 1000000 · e^(3950 × (1/353,15 − 1/298,15)) = 169000 Ω

✅ Expected resistance: ≈ 169 kΩ

The NTC 1 MΩ is designed to be integrated into an ultra high impedance voltage divider, where the measurement current remains in the order of a few microamperes.

🔹 Typical components

Component
 Function
NTC 1 MΩ Temperature sensor
R fixed (1 MΩ)
 Reference resistance
Microcontroller / ADC (24 bits)
 Analog lecture
100 nF capacitor
 Filtering
Power Supply 3.3 / 5 V
 Stable and clean tension
🔹 Functional diagram (ASCII)
  +3.3V / +5V
       │
     [Rfixe]
       │────► ADC (microcontroller input)
     [NTC 1MΩ]
       │
      GND
💡 Its very high resistance ensures negligible consumption, making it ideal for long-lasting sensors or systems without continuous power supply.

 We integrate any sensor into any probe 

Smooth tube probe

 Smooth tube 

Waterproof probe

 Waterproof

Bayonet probe

 Bayonet

Slot probe

 Slot

Ambient probe

 Atmosphere

Connection head probe

Termal block

Stick-in probe

Stick-in

Thread probe

Thread

Contact probe

Contact

Jacketed probe

Jacketed

PCBA Design

PCBA design

Winding probe

Winding

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