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Answer: There are two electrodes which are coupled together and integrated into a high frequency oscillator. When there is no dielectric material (the dielectric material is what is being sensed) the oscillator is tuned to be in the resting state. As a dielectric material enters the electric field of the sensor, the capacitance increases and oscillation begins. When the amplitude of oscillation reaches a high enough level, a change in signal state is triggered.
Standard catalog part numbers are NPN sinking devices but PNP Sourcing available on request.
CAP-100 or CAP-150 family is suited for detecting through a plastic or glass tank and is not intrusive.
The Cap-200 is suited for contact detection of liquids and must touch the media via a ½” NPT half coupling mounted to the side of the vessel. For metal tanks a shielded sensor is required.
Mounting the CAP sensor on the side of the tank is the best way to detect media level. Mounting on the bottom of the tank may give undesirable results and should be thoroughly tested as it is difficult to sense a thickness of the media. A slight film or droplets of media on the bottom surface of the tank may trigger the CAP. The set point can be tricky.
You can use a plastic tie wrap or double sided tape. For double sided tape, it is preferable to mount it over the bulls eye to minimize the gap between the sensor and the container. Glue is not recommended as the sensor will detect the glue.
It should be used for non-conductive medias and when mounting the CAP sensor on a metal bracket or metal mounting plate.
They are used for conductive medias and cannot be mounted on metal brackets or metal surfaces.
Yes, humidity or moisture on the sensor face can make the sensor unstable. Liquid droplets on the sensor face can cause the unit to become unstable. As a side note, dust and moisture have less of an effect on unshielded sensor than on shielded sensors.
Yes, factory calibration is available for large volume OEM applications. Call the factory for details. For non-OEM users, you must calibrate the CAP in the application with your media. Also be sure to turn the calibration pot ¼ to ½ turn past the point that the indicator light comes on as an added safety factor. Instructions will be supplied with each sensor.
Changes in Sensor or bottle position, bottle wall thickness, or fluid dielectric fluctuations can impair capacitance sensor performance and recalibration becomes necessary.
The CAP sensor has a 40-turn pot clutched. To set it back to the factory setting, turn the pot all the way to the end, then turn it back 20 turns. Then you should be ready to recalibrate in your application per instructions provided in the originally bulletin that came with the sensor.
When two shielded sensors are mounted side by side, the minimum distance between them must be greater than one time their width.
When two unshielded sensors are mounted side by side, the distance between them should be at least four times their width.
When two shielded or unshielded sensors are facing each other, they must be mounted eight times the housing diameter or width away from each other.
The MTBF is 782,472.61 hours.
CE approved ED Directives: 2006/95/EC-2004/108/EC Standards: EN 61000-4-3, EN 61000-4-20 Certification documents available upon request.
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