ETP21-H2 Temperature Transducer
Hydrogen Applications
-40°C to +100°C

ETP21R Temperature Sensor
-40°C to +125°C
A Temperature Transducer is a device that measures temperature and converts it into an electrical signal that can be processed by a control system. These transducers are widely used in industrial automation, automotive applications, railway systems, medical equipment, and more.
Advantages of Temperature Transducers:
- Accurate and Reliable Measurement – Utilizes the well-proven PT100 sensing element.
- Durability in Extreme Conditions – Operates across wide temperature ranges, resistant to shocks, moisture, and high pressures.
- Easy Integration – Available with different electrical connections and output types for seamless system compatibility.
Now, let’s review three major VARIOHM temperature transducer models, discussing their specifications, potential applications, and advantages.
1. ETP21 Temperature Transducer
The ETP21 is a versatile temperature transducer designed for industrial, automotive, and automation applications.
Key Features
- Accuracy: ±1.0% at room temperature.
- Environmental Durability:
- Temperature range: -40°C to +125°C.
- Shock resistance: 1000G.
- Vibration resistance: 16G (20-2000Hz).
- IP67 rating for protection against dust and water.
- Maximum Operating Pressure:
- M10 / G1/4: Up to 160 bar static.
- BC (Bird Cage) version: Up to 60 bar static.
- Output Options:
- 0-10V (Supply voltage: 12-32V DC).
- 4-20mA (Supply voltage: 10-32V DC).
- 0.5-4.5V (Supply voltage: 5V DC, ratiometric).
- Mechanical Construction:
- 304 Stainless Steel housing.
- Various process connections (G1/4, M10, BC).
- Weight: Approx. 30g.
Primary Applications
- Automotive and Agricultural Machinery – Monitoring engine temperature, hydraulic systems, and transmissions.
- Industrial Machines – Temperature control for oils and fluids in industrial processes.
- Robotics & Automation – Integration with smart sensors for temperature regulation.
2. ETP21H2 – Hydrogen-Compatible Temperature Transducer
The ETP21H2 is a specialized version of the ETP21, designed for hydrogen-powered systems and aggressive gas or liquid media.
Key Features
- Accuracy: ±1.0% at room temperature.
- Environmental Durability:
- Temperature range: -40°C to +125°C.
- Shock and vibration resistance similar to ETP21.
- IP67 rating.
- Pressure resistance of 160 bar (higher pressures available upon request).
- Output Options:
- 4-20mA (Supply voltage: 10-32V DC).
- 0.5-4.5V (Supply voltage: 5V DC, ratiometric).
- Mechanical Construction:
- 316L Stainless Steel housing for enhanced corrosion resistance.
- Weight: Approx. 30g.
Primary Applications
- Hydrogen Fuel Industry – Monitoring hydrogen temperature in storage, refueling, and distribution systems.
- Laboratories and Test Equipment – Used in reactor testing, electrolysis, and fuel cell applications.
- Petrochemical Industry – Measuring temperatures of aggressive liquids and high-pressure gases.
3. ETP21R – Railway-Specific Temperature Sensor
The ETP21R is specifically designed for railway applications, complying with strict safety and reliability standards.
Key Features
- Accuracy: ±1.0% at room temperature.
- Total Accuracy Across Temperature Ranges:
- -20°C to +85°C: ±2.0% FSO.
- -40°C to +125°C: ±3.0% FSO.
- Environmental Durability:
- IPX9K, IPX7, IP6X ratings (high-pressure water resistance, dustproof).
- Shock and vibration compliance per EN61373 and DIN EN 60068-2-27 standards.
- Electrical Properties:
- Output Signal: 4-20mA.
- Supply Voltage: 14.4V – 33.6V DC.
- Reverse Polarity Protection.
- Isolation Resistance: 100MΩ at 710V DC.
- Mechanical Construction:
- 17-4PH Stainless Steel for high durability and pressure resistance.
- M12x1 Electrical Connector.
- Weight: Approx. 80g.
Primary Applications
- Railway Control Systems – Monitoring temperature in bearings, brakes, gearboxes, and hydraulic systems.
- Railway Power Systems – Monitoring transformer and electrical component temperatures.
- Public Transport Systems – Used in temperature regulation of HVAC systems in electric buses and trains.
Comparison of the Three Models
| Feature | ETP21 (General Purpose) | ETP21H2 (Hydrogen) | ETP21R (Railway) |
|---|---|---|---|
| Accuracy | ±1.0% | ±1.0% | ±1.0% |
| Temperature Range | -40°C to +125°C | -40°C to +125°C | -40°C to +125°C |
| Max Operating Pressure | 160 bar | 160 bar (higher available) | 160 bar |
| Output Type | 0-10V, 4-20mA, 0.5-4.5V | 4-20mA, 0.5-4.5V | 4-20mA |
| Shock & Vibration Resistance | 1000G, 16G | 1000G, 16G | Railway standard compliance |
| Housing Material | 304 Stainless Steel | 316L Stainless Steel | 17-4PH Stainless Steel |
| Electrical Connections | Various options | Various options | M12x1 only |
The VARIOHM temperature transducers provide a precise, reliable, and durable solution for various industries – from industrial machinery and hydrogen applications to railway systems. Choosing the right sensor depends on the application’s requirements, accuracy demands, and the environmental conditions in which it will operate.




