AD7150 AD7746 level sensing demo

Q We have a requirement from one of our customer, where in we are suppose to measure the level of diesel in the generator. I thought of using AD7150 with the electrode PCB for this purpose. Before going to production, we thought of having a prototype. But i'm not clear of how to make the electrode PCB. Can you please guide me regarding what material to use and any precautions to be taken for this purpose. AD7150 will be interfaced to a microcontroller to monitor the capacitance value. A Pls refer to below for the response from our cap sensing product application engineer. the sensor design itself is not quite our area of expertise, although we try to help our customers as much as we can with the knowledge we collected from different applications using various sensor types connected to our CDCs. It is difficult to advice on the geometry/pattern/design of a sensor for a particular application, the tests we conducted with different sensor geometry/pattern/design were all experimental. I have no means of simulating what would be the best approach for a given application. The approach I take is that I usually get boards done with a variety of different sensor designs/patters and test which one would be the best suited for the intended application. However, I do not recommend the use of the AD7150 for such an application as the part is not factory calibrated, hence the overall capacitive input range can vary from part to part by ~20%. I recommend the AD7152 as it is factory calibrated and can be used in differential mode if necessary.

AD7150: Capacitive effects as conductive and non-conductive materials approach the sensor

Q If a finger, metal or water or other conducting materials approach the sensor, the capacitance values are decreasing. If a non-coductive plastic item approaches the sensor, first the capacitance values are decreasing but at closer distances the values appear to be increasing. So it is difficult to distinguish if a conducting object is approaching or a non-conductive object is moving away from the sensor. A The same phenomenon happens with both conductive and non-conductive materials. When a part is initially brought into the electric field, some charge is diverted to ground and a lower capacitance is measured on the CINx pin. When it is close enough, the part increases the effective ε and this increases the capacitance. Conductive materials will divert more charge to ground than non-conductive materials; therefore the drop in capacitance has a bigger effect than the increase in ε.