Compact and cost-effective zirconium-dioxide oxygen transmitters

The OXY-FLEX Series from Process Sensing Technologies (PST) is a range of compact and cost-effective oxygen transmitters that measure percentage level O2 in many applications such as combustion efficiency and emissions monitoring, breathing air generation and moisture monitoring in commercial bakery ovens.

OXY-FLEX is configurable to measure either 0-25% or 0-100% oxygen with 4-20mA, 0-10VDC and serial outputs, and offers manual or automatic calibration to suit the customer’s needs. The gas sensor uses a unique zirconium dioxide sensing technology that can readily withstand extreme temperatures up to 400degC and aggressive industrial environments.

OXY-FLEX has an IP66 rating and options for food grade stainless steel housings for bakery ovens and commercial steam generators.

Oxygen Sensor Technology

Zirconium dioxide sensors are based on the principle of a non-depleting solid-state sensor, which contains two pieces of ZrO2 with a small hermetically sealed chamber between them. One of the discs acts as a reversible oxygen pump, used to fill and empty the chamber; the second disc measures the ratio of the oxygen partial pressure difference and generates a corresponding sense (Nernst) voltage. A heater surrounding the sensing element produces the heat required for the ZrO2 to act as a pump. The time taken for the pump to achieve specific minimum and maximum pressures within the chamber is a measure of the partial pressure of oxygen in the environment. Al2O3 discs filter particulate matter and neutralize unburnt gasses to avoid contamination, which might lead to unstable readings. The sensing technology and stainless-steel construction allow Zirconium Dioxide oxygen sensors to be used in environments where extreme pressure, temperature and high humidity are present.

OXY-FLEX Series Design

The OXY-FLEX probe can be mounted directly on the housing unit or on a shielded cable. The housing is a sealed, die-cast aluminium or optional stainless-steel enclosure. Industry standard analogue and digital outputs with a pin on the connector dedicated for remote calibration are included, and supplied with test certificate, mating connector and cable options. The OXY-FLEX unit is easy to install and integrate into existing systems as no specialist software is required.

Calibration of the sensor is simple with a single point calibration in fresh air all that is needed for most applications.

OXY-FLEX oxygen transmitters offer four configuration options, with three choices of probe length (200mm, 400mm and 600mm). The ability to operate in process temperatures up to 400degC make the sensor suitable for a wide range of applications in metal treatment, combustion control and food production.

Oxygen Transmitter Applications

OXY-FLEX transmitters can be used in numerous applications, typically combustion control of industrial boilers, burning oil, gas, coal or biomass; incubators; composting probes and bakery or commercial steam ovens.

Combustion processes require the correct oxygen-to-fuel ratio as it directly affects boiler efficiency. Too little oxygen results in incomplete combustion, creating harmful emissions. Incorrect combustion can lead to fuel waste, increased levels of toxic emissions and potentially damaging the combustion system, and therefore, environmental and financial impacts can be significant. Fuel consumption and system value overheads are high in large scale industrial and commercial boilers and furnaces. To see return of investment and minimal running costs the operation must be kept at peak efficiency. OXY-FLEX oxygen transmitters from PST can help customers optimise their boiler combustion efficiency.

Bakery ovens control the moisture levels at high temperatures. OXY-FLEX can operate in temperatures up to 400degC and as the sensor principle monitors the partial pressure of Oxygen, changes in water vapour pressure are indicated to allow control of the correct amount of moisture in the process.

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