Gas Sensing Technologies

Thermal conductivity for binary gas analysis

All gases conduct heat to differing degrees, and the amount of heat transferred by a gas is determined by its 'Thermal Conductivity' (TC) value. This property can be exploited in sensing because each gas has a different TC value. Michell’s Thermal Conductivity Sensor uses this property to accurately measure one of the two gases present in a sample of a binary or pseudo-binary mix.

The sensor uses matched thermistors forming one half of a Wheatstone bridge. One thermistor is in the sample cell, the other is housed in a reference chamber (sealed and flowing reference versions are available). The whole assembly is heated to +50°C to ensure an iso-thermal environment, where the condition of the sample is consistent, providing an accurate and stable platform for measuring the target gas concentration.

When gas is flowing through the sample chamber, heat is drawn from the thermistor and this changes one element of the bridge. A current is required to keep the bridge balanced and from this, the TC value of the gas can be determined.

Plasma emission detector (PED)

LDetek’s Plasma Emission Detector (PED) ionizes the sample gas which releases energy in the form of light. Each impurity emits a characteristic light at a specific wavelength, which is collected though a filter to discriminate the undesired wavelengths. The intensity of the light is proportional to the amount of each impurity present which is proportionally converted into an electrical signal via a photodiode. The signal is subsequently amplified, contributing to this technique being extremely sensitive for trace level impurities measurements.

Infrared Gas Sensor

Dynament infrared sensors operate by using nondispersive infrared (NDIR) technology to monitor the presence of a target gas. The sensor contains a long-life tungsten filament infrared light source, an optical cavity into which gas diffuses, a dual temperature compensated pyroelectric infrared detector, an integral semiconductor temperature sensor and electronics to process the signals from the pyroelectric detector.

These NDIR sensors offer fast-response and high-resolution for the detection of hydrocarbons (including methane and propane), carbon dioxide, and nitrous oxide.

The Dynament sensor portfolio also includes a revolutionary Dual-Gas High Resolution Methane/Carbon Dioxide Sensor providing the capability to simultaneously monitor methane and carbon dioxide in a single sensor package while only consuming the power of a single infrared sensor.