MZ6 | GUILCOR SENSORS

MZ6
Temperature sensors

Durable PTC sensor for industrial equipment and embedded applications, ensuring reliable thermal protection.

Maximum precision
+/- 5°K

Minimum temperature
-20°C

Maximum temperature
+180°C

Minimum dimensions
2,5 x 10

Response time
Medium

Self-heating
Low

Price
Medium

Drift
Low

What is a MZ6 sensor ?

The MZ6 is a threshold PTC thermistor used as a thermal protection sensor in motors, transformers, and power systems.

Its resistance remains low and stable up to a specific switching temperature (typically between 60 °C and 180 °C, depending on the version), then increases sharply, indicating overheating.

It complies with DIN 44081 / 44082 standards, ensuring its interchangeability with other protection PTCs.

Operating principle

Under the nominal temperature (Tₙ), the resistance is low (about 150 Ω).

As soon as the temperature reaches the threshold, the resistance increases exponentially to several tens of kilo-ohms within a few degrees.

This transition is detected by a PTC control relay, which cuts off the control circuit to protect the system.

Temperature (°C)	Typical resistance (Ω)
20	150
80	160
100	170
120 (Tₙ)	1650
140	4500
160	10 000
180	20 000

🧠 This sharp trigger curve makes it a reliable safety component for electromechanical systems.

Technical specifications

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

Wiring configuration

Type	Description	Precision
2-wire	Series assembly in the detection circuit.	✅ Standard
Multiple chain	Several MZ6 in series to monitor multiple engine zones.	🏆 Industrial
Integrated	Stuck or molded in the motor winding.	💡 Direct thermoprotection

Self-heating

The measurement current being limited to a maximum of 2.5 mA, self-heating is negligible, ensuring purely external temperature detection.

Application areas

⚙️ Thermal protection of three-phase motors

🔋 Monitoring of transformers and power inductors

🚗 Battery protection systems and variable speed drives

🧱 Industrial applications compliant with DIN 44081/82

🧠 Sensors integrated into thermal cut-off relays

Should I choose a MZ6 sensor ?

Strengths points

🧱 Robust and proven
→ The MZ6 has been an industrial standard for decades — reliable, simple, and fully compatible with DIN 44081/82 detection modules.
⚡ Quick and clear trigger
→ Its steep resistance curve ensures instant and reproducible overheating detection, without complex electronics.
🔩 Adaptable to all motor windings
→ Thanks to its compact size and 2.5 kV insulation, it can be directly integrated into the winding or molded into the resin.

Weaknesses points

🌡️ Non-linear
→ The MZ6 is not suitable for continuous temperature measurement: it only provides a threshold exceedance signal.
🔋 Limited measurement current
→ A current greater than 2.5 mA can distort the triggering temperature and may even damage the component.
💡 Requires a dedicated PTC relay
→ To function properly, the sensor must be paired with a compatible DIN detection module, which adds additional cost and bulk.

Useful information

Here is some useful information regarding the MZ6 sensors.

Tolerances and precision classes

The MZ6 sensors comply with DIN 44081 / 44082 standards, which define their switching characteristics, tolerance, and dynamic behavior.

They are not classified as A/B/C like linear PTCs, but according to the nominal triggering temperature (Tₙ).

Type MZ6	Nominal temperature (Tₙ)	Tolerance (Tₙ)	Resistance at 25 °C (R25)	Resistance to Tₙ	Applicable standard
MZ6-60	60 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44081
MZ6-80	80 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44081
MZ6-120	120 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44081
MZ6-150	150 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44082
MZ6-180	180 °C	±5 K	150 Ω ±20 %	≥ 1650 Ω	DIN 44082

🔹 Remarks:

All models exhibit a nearly constant resistance (<200 Ω) up to about 20 K before Tₙ.
Beyond the threshold, the resistance increases exponentially (up to several tens of kΩ).
The tolerances ensure complete interchangeability between manufacturers compliant with DIN.

Application example – Simplified equation

The MZ6 exhibit a bistable threshold behavior.

Their evolution can be represented by two distinct regimes: linear before Tₙ, exponential after Tₙ.

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

{ R_N × e^{β(T - T_N)} for 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

• β ≈ 0.25 K⁻¹

🔹 Example 1: normal regime (T = 80 °C, threshold 120 °C)

R(80) = 150 × [1 + 3×10⁻³ × (80 - 25)] = 150 × 1.165 = 174.8 Ω

✅ Result: the engine is functioning normally, no overheating.

🔹 Example 2: overheating (T = 140 °C)

R(140) = 1650 × e^(0.25 × (140 - 120)) = 1650 × e^5 ≈ 1650 × 148.4 = 244,000 Ω

✅ Result: the resistance rises to ≈ 240 kΩ, instantaneous cutoff signal.

🔹 Practical notes

The MZ6 acts as a progressive thermal switch.

It does not allow for any precise temperature measurement, but ensures reliable and reproducible threshold detection.

The R(T) curve remains stable after several thousand thermal cycles.

Integration diagram in an electronic system

The MZ6 is used in a protection circuit via a PTC detection relay.

Multiple sensors can be connected in series to monitor different areas of the same motor.

Component	Function
MZ6 (Threshold PTC)	Nominal temperature sensor
PTC detection module / Thermal relay	Threshold exceedance triggering
Power Supply (24 V DC)	Feed the control circuit
Power contactor / relay	Turn off the engine or the protected system

🔹 Functional diagram (ASCII)

        +24 V
          │
     [PTC Detection Relay]
          │
     ├────┴────┐
     │         │
 [MZ6-120]  [MZ6-120]
 (in series on 2 windings)
     │         │
     └────┬────┘
          │
         GND

🔹 Operating Principle

1️⃣ Each MZ6 sensor is inserted into a critical area of the engine.

2️⃣ As long as T < Tₙ, the resistance remains low → PTC relay closed → normal operation.

3️⃣ As soon as a sensor reaches its threshold → resistance > 1.5 kΩ → relay opens the circuit → immediate engine shutdown.

🔹 Best Practices

🧩 Use sensors with the same Tₙ in a series chain.
⚡ Never exceed 2.5 mA of test current.
💧 Avoid direct contact with humid environments (molding or varnishing recommended).
🧲 Use a DIN 44081/82 certified relay to ensure compatibility.
🔄 Replace all PTCs during preventive maintenance to maintain thermal consistency.