Thursday, February 23, 2012

What are Electrochemical sensors?

Electrochemical sensors are devices that measure flue gas constituents (O2, CO, NO, NO2, SO2, H2S) through the principle of ion selective potentiometry The sensor contain a electrolytic matrix that is designed for a specific gas to be detected. Two or three electrodes (again gas specific) are placed in this matrix and an electrical field is applied. Flue gas enters the sensor and chemically reacts (oxidation or reduction) on the electrode releasing electrically charged particles (ions). This reaction causes the potential of this electrode to rise or fall with respect to the counter electrode. With a resistor connected across the electrodes, a current is generated which is proportional to the concentration of gas present. The output is converted then displayed as a concentration (typically in ppm, percent, or as a mass unit (i.e. lbs/hr or mmbtu).

Standard electrochemical sensors are affected by various environmental factors including: temperature, pressure, and other combustion gases. However, testo sensors are designed to eliminate these effects. Mounted on each sensor is a circuit board that contains calibration data, linearity data, and other critical information. This technology enables the sensor to be pre-calibrated at testo and installed in the field as a simple plug-in device. No need to have calibration gases on site. Additional technological advancements in sensor and analyzer design include the use of:
  • Continuous temperature compensation to provide accurate response regardless of ambient temperature fluctuations.
  • Control of sample pressure and automatic flow rate monitoring to eliminate pressure related effects.
  • Sensor temperature control by using heated thermoplastic sensor blankets.
  • Integrated on-board interference filter media that eliminates the hassle of replacing NOx beads
  • Automatic cross compensation for interference gases.
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