Level measurement

Contec Liquid Measurement, a Contec division.

A capacitive sensor is based on changes to an alternating electric field. A liquid's fill level, in a tank, for instance, influences the strength of the alternating field that the sensor generates. The sensor uses this change in electric capacity as a measuring signal.

For fill level measurement with a capacitive fill level sensor, exact information about the liquid is needed ahead of time. Sensor precision depends on the dielectricity constants of the medium to be measured. If the liquids or fuels are to change (diesel or biodiesel, for instance), Contec offers special solutions such as sensors with manual or automatic calibration.

Typical application areas for capacitive fill level sensors are tanks of motor sport vehicles, utility vehicles and agricultural and construction machinery and in mobile tanks. Capacitive sensors can measure liquids such as coolant, lubricant, fuel and motor and hydraulic oil.

Mechanical fill level indicators can be observed and evaluated in a fraction of a second, much like a clock face, where the position of the hands is enough to tell the time. Fill level indicators are simple and robust in design and can easily be adapted to individual tank dimensions, sometimes by simply shortening them. They require no power connection. Contec fill level indicators can also be retrofitted with an addition signal output with a Twinsites indicator face.

Fill levels in a tank can be measured by such means as electrically capacitive, radar-guided or mechanical equipment. The COLM product range also includes level switches for detecting when a liquid is at a certain level.

The most commonly used Contec sensors are capacitive and electromechanical sensors. Fill levels can also be monitored optically, hydrostatically or with ultrasound.

Contec fill level sensors can be used in many ways. For example, they detect the fill levels of liquids in reservoirs and storage tanks. They also monitor critical process states in such situations as when a hydraulic tank is emptied or the inadvertent overfilling of a tank must be prevented.

Other possible uses include the following:

• monitoring oil fill levels in machine and plant engineering
• measuring the fill level of cleaning fluid and cooling lubricant
• preventing inadvertent overfilling/emptying of open and closed containers, hydraulic tanks, silos and storage tanks

If only one level or switching function (such as a maximum or minimum warning signal) is needed, the COLM fill level switch is the right mechanism. The switches are used classically to monitor pumps or record warning signals when liquid falls below a certain level.