Introduction
Electrolytic tilt sensors are non-signal conditioned sensing elements. The function of fan electrolytic tilt sensor is to measure an angle or a null or level position with reference to gravity. The angle may be expressed in anyone of the following: degrees, arc minutes(1/60th of a degree) or arc seconds(1/60thh of an arc minute). These angles are generally referenced to a perpendicular line to gravity called a null or a zero point. The amount of tilt from this point can be expressed as either positive or negative angle[2].
A single axis sensor would only measure an angle in one direction. To measure an angle in all directions, for example, to a compass heading, a dual axis sensor or two singles axis sensors mounted 90 degrees to each other would be required. This would allow the measurement to be made in any direction by combining the readings of both axes as seen in figure 1.
Structure and operation
The tilt sensor functions like a liquid potentiometer. The electrically conductive fluid creates a variable resistance between the electrodes. When the sensor is in the null or balanced position, the resistances between the center electrode to each outside electrode are equal. Tilting the sensor from its balanced position changes the two resistances producing an electrical output proportional to the tilted angle. The major electrolytic salts are chosen from metal cations, such as sodium, potassium, lithium, calcium and cesium, of which the ionic species offer good conductivity at every level of dilution. The electrolytic salts are also selected from anions, such as nitrate, carbonate, acetate and hydroxide, which resist chemically combining with the metallic elements of the metal electrode materials. Solvents may include methanol, ethanol, butanol, propanol and isopropanol that provide the ability to control the viscosity of the electrolyte, related directly to the response time of tilt sensor[1].
Electrolytic tilt sensors must be operated in the AC mode. Any DC will cause the level to become unstable and even inoperable. The amount of current through the level must not exceed the maximum. Currents that are above the typical recommended value will cause the level to self heat and the readings will drift. The impedance value of the level must be specified to match the type of circuit used in order to limit the current.
References
Wong,T.D., Evaluation of Electrolytic Tilt Sensor for Wind tunnel Model Angle-of-Attack (AOA) Measurements, Langley Research Center, NASA, USA
- The Fredericks Company(2008). Retrieved from http://www.frederickscom.com/sens_tech_select.tpl