Gas sensing Inside the non-depleting Servomex Paramagnetic sensor

Using the right gas sensing tech for industrial applications

Selecting the right gas sensing technology for your industrial application will provide the best results for efficiency, safety and quality. In this article, Servomex explores different sensor technologies that are available One of the key factors in selecting the right


ffective gas analysis is an essential part of many industrial processes, supporting process efficiency and

control, product quality, safety, and emissions monitoring applications. It is used in an extensive range of market

sectors, including power generation, industrial gases, hydrocarbon processing, metals and mining, medical gases, and semiconductor manufacture.

instrumentation for gas analysis is the sensor technology involved. The sensor is the heart of the gas analyser, and is the means by which the gas of interest is detected and measured. There are many different sensing technologies, some specific to a certain gas, and others configurable to measure many different gases. Each has its advantages and disadvantages depending on the application selected, so it is important to utilise the correct technology for individual conditions. Servomex currently offers 15 different sensing technologies, so has a wide choice when it comes to selecting the best fit for both plant and application requirements.

This means that there is no need to shoehorn a

gas analyser into a process measurement point for which it is poorly suited – instead, the most efficient and cost-effective solution can be used.


For example, oxygen (O2) can be measured by Paramagnetic, Coulometric, Zirconia and Tunable Diode Laser (TDL) technologies. Highly specific to O2, Paramagnetic technology

The Paracube Modus Paramagnetic sensor, as manufactured by Servomex’s sensor brand Hummingbird


delivers highly accurate measurements and a fast response to changing concentration levels. Paramagnetic cells are non-depleting, so should

never need replacement. Their performance does not deteriorate over time, giving significant benefits

to ongoing maintenance costs and sensor lifespan. Zirconia sensors are both reliable and flexible,

with an excellent response to changes in O2 levels. Their major advantage is the ability to be used for in-situ analysers, eliminating the need for extractive sampling equipment. While Paramagnetic and Zirconia solutions are

highly effective for percentage O2 measurements (and parts per million readings in the case of

Zirconia), an electrochemical sensor is required to reach the extremely low levels demanded by electronics-grade gas quality control. Coulometric sensors use a long-life

electrochemical process that enables direct O2 measurements at trace and ultra-trace levels, without needing periodic replacement or producing the false low readings associated with traditional fuel cell sensors. Servomex’s Coulometric sensor also

provides a very fast response to changes in O2 concentrations, which is highly beneficial for

users who deal with upset-prone applications. It can also handle both flammable and non- flammable samples. TDL is the newest of these sensing technologies, and can be used to measure a wide

range of gases, not just O2. However, when the analyser is configured to the target gas, it is highly stable and specific to that gas, avoiding cross- interference from other compounds. While the other three sensors measure the oxygen concentration at a particular point,

June 2020 Instrumentation Monthly

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