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Level Sensor ApplicationsCapacitive sensors The operation of these level sensors is based on a dielectric measuring method. All media which surround the sensors measuring electrode, built into the tip of the probe, change the state of dielectric balance between the measuring electrode and the surrounding space. This disturbance in the balance triggers a switching command inside the device. The balance can be adjusted with a built-in potentiometer so that materials with different bulk densities and correspondingly different dielectric constants can be measured optimally. Metallic or metal clad vessels should be earthed. In the case of plastic vessels filled with electrically conductive materials, the latter should be earthed. In the case of plastic vessels filled with non-conducting materials, an earthed metal band applied on the outside of the vessel may be used as a counter-electrode. Installation At the side installation of capacitive sensors we prefer to put the sensor tip on an angle of 20 degree to protect material build-up.
Medium adjustment for capacitive sensors Level sensors are set in such a way that they switch upon contact with a medium. The medium adjustment should, if possible, take place without removal under operating conditions. If the built-in part of the sensor can be completely submerged or covered during operation, the adjustment must also take place in this state. If only medium contact is possible, the adjustment takes place upon contact. The trimmer potentiometer is protected by a plastic bolt. This bolt must be removed before the desired sensitivity is set. Turning it clockwise increases the response sensitivity. The adjustment potentiometer is turned until the switch output switches through (normally-open contact). You achieve the switching point safety by continuing to turn the potentiometer half a turn to one turn. Devices with a LED line are adjusted to two green LEDs. Once the medium adjustment has taken place, the plastic bolt must be re-fitted. Laboratory adjustment If adjustment cannot be carried out with the sensor mounted in operating position, it can be performed upon a similar vessel. This vessel, must, however, be set upon an earthed metal plate, or, the liquid within the vessel must be earthed by means of an introduced wire. The minimum height and minimum diameter of the experimental vessel should be about 10 cm. If setting is correct, the filling level monitor reacts correctly if 50% of the electrode diameter is covered. When mounted vertically, sensors react upon contact with the medium. Reaction time lag is less than 0.25 sec. Sealings The sealings used for our sensors are made of PTFE, NBR, FPM or AFM. For water applications with water temperatures up to 150 °C and with pressures less than 5 bar, EDPM O-rings must be used. If the temperatures exceed 100 °C or the pressures are higher special seals are necessary (2). When ordering sensors for such applications, the seals should also be ordered.
Threads The threads of the sensors in this prospectus are manufactured to DIN ISO 228-1, tolerance class B. They are designated with (") or (G). If it is necessary to combine different threads, e.g. the sensor-thread made to DIN ISO 228-1 and an inner thread made to DIN ISO 229, such inner thread must be widened by a thread drill. Sensors for explosion hazardous areas Level sensors for use in zone 0 or zone 20 are operated with the associated amplifiers listed in the respective connection chart. The control units are always mounted outside of the ex area. Sensors of the series KGFT...Ex are used in conjunction with an intermediate amplifier, which is approved for installation in zone 1. Optical level sensors UF../UR.. Optical sensors react to a change of the refraction index within the proximity of the sensor tip when being immersed into fluid. The sensor does not have to be adjusted. In rare cases, the container wall or particles within the fluid may reflect the light emitted by the sensor and thus interfere with the fluid detection. A trial run is recommended in such instances. The sensors are designed to be used with the respectively listed fluids under normal conditions. The chemical compatibility and technical suitability of the sensor should be tested when used with unlisted fluids.
Powelectrics can provide complete remote tank level monitoring solutions using their range of IN4MA GSM Telemetry products. Please click here to be redirected to the IN4MA site and learn more.
All pages in section: Level Sensors
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