Electronic Circuits for Polarographic Oxygen Sensors
A polarographic oxygen sensor (POS) is a two-terminal chemoelectric transducer; a suitable polarizing voltage across the sensor leads produces an output current which, ideally, is proportional to the partial pressure of oxygen in the sample. In membranecovered sensors this signal is quite small and current is first converted into a voltage and then amplified to drive either a meter or a strip chart recorder or for input to an analog-to-digital converter. Membrane-covered POS show a large dependence on temperature, the signal increasing by 1%–6% for a rise of 1°C . Consequently measurements have to be made under thermostatic conditions or there has to be some method of compensating the temperature effect. If a readout in units of concentration is desired, a correction for the variation of oxygen solubility as a function of temperature (App. A) must also be made. A block diagram for a circuit for a temperature-compensated oxygen detector is shown in Fig. 1.
KeywordsElectronic Circuit Operational Amplifier Temperature Compensation Voltage Divider Polarize Voltage
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