MZ8 | GUILCOR SENSORS

MZ8
Temperature sensors

Advanced PTC sensor offering accurate temperature measurement and stability for electronic circuits and control systems.

Maximum precision
+/- 5,0°K

Minimum temperature
-25°C

Maximum temperature
+200°C

Minimum dimensions
2,5 x 9

Response time
Medium

Self-heating
Low

Price
Medium

Drift
Low

What is a MZ8 sensor ?

The MZ8 is a next-generation PTC threshold sensor designed for the direct thermal protection of electrical and electronic equipment.

Its R(T) curve is identical to that of the MZ6, but it offers better long-term stability, superior mechanical resistance, and universal compatibility with PTC relays DIN 44081/82.

MZ8 sensors are often delivered in sets of 3 for monitoring the three windings of a three-phase motor.

Operating principle

Like all threshold PTCs, the MZ8 remains stable up to its nominal temperature (Tₙ), after which its resistance increases exponentially.

This causes a clear logical signal (ON/OFF detection) when overheating is reached.

Temperature (°C)	Typical resistance (Ω)
20	150
100	170
120 (Tₙ)	1650
140	4500
160	10 000
180	20 000
200	30 000

The reproducible behavior of the MZ8 makes it perfectly suited for series PTC chains, with no recalibration necessary.

Technical specifications

Parameter	Typical Value
Nominal resistance (Tₙ)	60°C to 180°C depending on the model
Resistance at 25 °C	150 Ω ±20 %
Resistance to Tₙ	≥ 1650 Ω
Maximum measuring current	2,5 mA
Electrical isolation	≥ 2,5 kV
Response time	3 to 5 s
Case	Epoxy, ceramic, or glass
Standard	DIN 44081 / 44082

Wiring configuration

Type	Description	Precision
2-wire	Simple assembly (series in the detection circuit).	✅ Standard
3-wire	Three-phase motor surveillance (U/V/W).	🏆 Industrial
Integrated	Coated in resin or winding.	💡 Direct thermoprotection

Self-heating

With a measurement current ≤ 2.5 mA, self-heating remains below 0.5 °C, ensuring reliable measurement without false alarms.

Application areas

⚙️ Protection of three-phase motors and servomotors

🔋 Thermal monitoring of transformers and variable speed drives

🚗 High-reliability automotive systems (batteries, ECU)

🧱 Industrial equipment standardized DIN 44081/82

🧠 Integrated thermal protection in power modules

Should I choose a MZ8 sensor ?

Strengths points

🧩 Universal Compatibility
→ The MZ8 fully complies with DIN 44081/82 standards, making it compatible with all PTC relays and detection modules on the market (Siemens, ABB, Schneider, etc.).
⚙️ Exceptional long-term stability
→ Thanks to its improved encapsulation and high-purity doped material, it offers consistent threshold accuracy, even after hundreds of thermal cycles.
🔋 Ideal for multi-sensor networks
→ Often delivered in triplets (U/V/W), the MZ8 allows for monitoring multiple motor windings with a single, reliable signal, without synchronization drift.

Weaknesses points

🌡️ Non-linear sensor
→ The MZ8 remains a threshold sensor, unsuitable for continuous temperature measurement — it only signals a limit breach.
💰 Unit cost higher than the MZ6
→ Its encapsulated design of better quality makes it slightly more expensive than the previous generation, at equivalent performance.
⚡ Dependency on the detection module
→ It cannot operate alone: it must always be paired with a compatible PTC relay to utilize the cutoff signal.

Useful information

Here is some useful information regarding the MZ8 sensors.

Tolerances and precision classes

The MZ8 comply with DIN 44081 / 44082 standards, which specify the tolerance range of the switching point (Tₙ), the nominal resistance at 25 °C, and the transition behavior.

They are designed to ensure reproducible triggering, even after numerous thermal cycles.

Type MZ8	Nominal temperature (Tₙ)	Tolerance (Tₙ)	Resistance at 25 °C (R25)	Resistance to Tₙ	Applicable standard
MZ8-60	60 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44081
MZ8-80	80 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44081
MZ8-120	120 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44081
MZ8-150	150 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44082
MZ8-180	180 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44082
MZ8-200	200 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44082

🔹 Remarks:

The MZ8 sensors exhibit a more stable trigger curve than the MZ6, particularly in the 150 °C and 180 °C models.
The resistance remains nearly constant (<200 Ω) up to about Tₙ − 20 K, then increases exponentially beyond that.
Their doped ceramic structure ensures a threshold reproducibility of ±1 K after 1000 cycles.

Application example – Simplified equation

The behavior of the MZ8 can be represented by two distinct areas:

R(T) = { R₀ [1 + α(T - 25)] if T < T_N

{ R_N × e^{β(T - T_N)} if T ≥ T_N

with:

• R₀ = 150 Ω: resistance at 25°C

• α ≈ 3 × 10⁻³ K⁻¹

• R_N = 1650 Ω: nominal resistance at the threshold temperature

• β ≈ 0.25 K⁻¹

🔹 Example 1: normal regime (T = 100 °C, model MZ8-150)

R(100) = 150 × [1 + 3×10⁻³ × (100 - 25)] = 150 × 1.225 = 183.8 Ω

✅ Result: normal operation, no overheating detected.

🔹 Example 2: overheating (T = 170 °C)

R(170) = 1650 × e^(0.25 × (170 - 150)) = 1650 × e^5 ≈ 1650 × 148.4 = 244,000 Ω

✅ Result: at 170 °C, the resistance exceeds 240 kΩ, causing the immediate opening of the PTC relay.

🔹 Practical notes

The MZ8 does not provide continuous measurement, but a very clear transition between "OK" and "OVERHEAT."
Its behavior is highly reproducible, allowing for consistent detection among multiple sensors in series.
The test current must always remain < 2.5 mA to avoid a parasitic temperature rise.

Integration diagram in an electronic system

The MZ8 is used in a thermal cutoff circuit powered by low voltage (often 24 V DC), coupled with a PTC detection relay.

This setup provides immediate protection for motors, windings, or transformers as soon as a threshold is reached.

🔹 Typical components

Component	Function
MZ8 (Threshold PTC)	Thermal detection element
PTC relay module DIN	Analyze the resistance and open the contact in case of overheating
Power Supply (24 V DC)	Order source
Motor contactor	Automatic power circuit disconnection

🔹 Functional diagram (ASCII)

        +24 V
          │
     [PTC relay module]
          │
     ├────┴────┐
     │         │
 [MZ8-150]  [MZ8-150]
 (in series on 2 windings)
     │         │
     └────┬────┘
          │
         GND

🔹 Operating Principle

1️⃣ The PTC relay sends a measurement current < 2.5 mA in the sensor chain.

2️⃣ As long as T < Tₙ, the total resistance remains < 750 Ω → relay closed → normal operation.

3️⃣ As soon as a sensor reaches Tₙ → total resistance > 4 kΩ → relay opens → immediate safety cut-off.

🔹 Best Practices