Hydrogen Sensor Evaluation Best Practices
During the evaluation process, it is often required to test sensors to ensure compatibility with specifications and real world applications. This was created to help developers quickly and easily test the NTM SenseH2® hydrogen sensor. Proper testing of the NTM SenseH2® will ensure that the sensor meets the needs of the application.
Setup and Powering the Sensor
- Power the device using a DC power source between 12-24VDC by making contact with connector pins 3 (black, -) and 4 (red, +)
- Pins 1 (blue, +) and 2 (black, -) are used to measure the 0-5V analog output.
- The two black wires are interchangeable and are provided as a common negative for convenience.
Measuring the Sensor Output
- The sensor output will read 0.5V momentarily after the sensor is turned on. Once the output switches to 1.0V, the sensor is ready to detect hydrogen.
- Start-up typically takes less than 10s to be ready to test
- Depending on the amount of time the sensor was turned off, the sensor may require several hours to achieve full accuracy after start-up.
- The sensor is designed to operate accurately over a wide range of humidity conditions. If the sensor is being tested on a gas bench using bottled gases, then the gas feed should be humidified to 5-95% RH.
The sensor is a point detector – it will only measure what is directly in front of the sintered metal inlet on the sensor. NTM Sensors sells test kits and calibration kits which come with a fixture designed to deliver gas directly to the sensor inlet. If tests are being done using a calibrated hydrogen/air blend, then it is recommended that this fixture is used. Releasing a calibration gas in the open air in front of the sensor may not result in sensor outputs matching the concentration of gas released. The sensor inlet is not designed to be pressurized. Never connect a gas line directly to the sensor inlet in a manner in which it will cause the sensor chamber to be pressurized.
Test Conditions to Avoid
- 0% humidity: Accuracy will be affected if the sensor is tested in 0% humidity conditions for extended periods of time.
- Hydrogen without oxygen present: The sensor is designed to operate in air and will be damaged if exposed to even small amounts of hydrogen without oxygen present, excessive hydrogen concentrations exceeding the LFL, or any other conditions which would result in a reducing condition at the sensor element. If the sensor is exposed to such conditions, the sensor output will go to a 4.75V error state and the sensor will remain in this state until the power is cycled. If the sensor does not return to a 1.0V output signal, then the sensor has been damaged by the reducing condition and should be replaced.
- Pressurization: The sensor inlet is not designed to be pressurized. Never connect a gas line directly to the sensor inlet in a manner in which it will cause the sensor chamber to be pressurized.