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Figure 3: AC Bridge Circuit

Another way to energize the level is to excite the outer electrodes and read from the center as shown in figure 4. This method will ensure that only the ratio of the impedance is measured and not the absolute value of the impedance. The electrolyte's impedance  over the desired temperature range  must not cause the current through the level to exceed the maximum value. Since the impedance is inversely proportional to temperature, an increase in temperature would cause an increase in current.

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Figure 4: AC exciting outer electrodes

The output ports of a micro-controller are a good example of a drive circuit for thee level, as long as each port exhibits equal source and sink currents thus preventing any DC component to the level. The output can be sampled between each port change by an analog to digital converter.

References

1. Wong,T.D., Evaluation of Electrolytic Tilt Sensor for Wind tunnel Model Angle-of-Attack (AOA) Measurements, Langley Research Center, NASA, USA

2. The Fredericks Company(2008). Retrieved from http://www.frederickscom.com/sens_tech_select.tpl
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