Feldmuehle_V2.6

The FMV2.6.3 is a high precision Field Mill for atmospheric research with integrated computing and control device using a Raspberry Pi 4 for computing purpose. It measures the static electrical field of the atmosphere without any current (fully passive) through its capacity sensor. The Sensor (the system by of the rotor and sensor plate) leads to an integrated 4 stage amplifier which can be steered digitally by the RaPi4 (Software). The RaPi4 also receives the analog transformed signal by an 18 bit AD for further processing. By design thus, the sensor needs high quality resistors, see BOM. The project requires an own power supply and sensor plate (see links to further projects below). The housing, a rotor, an electric DC motor with a shaft that is conductive to ground, a photoelectric barrier and some shielded and well dimensioned wires are not further described in here but required. See Technical Information and Link to Stefan's field mill below as well. All this parts can be designed individually and there are no plans currently available, but good understanding of electronics and EM needed.  * The Power Supply for the FMV2.6.3 can be found here: [https://oshwlab\.com/TheSkunk/feldmuehler\_v2\_netzteil](https://oshwlab.com/TheSkunk/feldmuehler_v2_netzteil) * The Sensor Plate can be found here: [https://oshwlab\.com/TheSkunk/feldmuehle\_v2\-6\-3\_sensorfeld](https://oshwlab.com/TheSkunk/feldmuehle_v2-6-3_sensorfeld) * The attached document *FMV2\_6\.3\_Projektmappe\_20240724\.xlsx* describes the physics and simulations (LT-spice) and thus helps to understand the design characteristics of the FMV2.6.3. * The first project (V1.2) can be found here: [https://www.mikrocontroller.net/topic/511801](https://www.mikrocontroller.net/topic/511801) **Technical and Historical Information:** The design of the measuring circuits is generally based on the design of [Stefan Kneifels field mill (website in German)](https://www.qsl.net/dh1stf/) from the 08.03.2005 which is still a valid and solid foundation of the whole project. It can be used to prove the current circuit design and the schematics of the FMV2.6.3. There are generally some differences (improvements) but not effecting the basic circuit design itself, like Stefan's field mill uses a 2 blade rotor and the FMV2.6.3 uses a 4 blade rotor and thus an 8 field sensor plate to make it more accurate. As well, Stefan's field mill produces only an analog output (-5 up to +5 V for an intermediate range of Vm), whereas FMV2.6.3 is fully digitized with its integrated 18 bit AD, it can automatically switch between 4 different measuring ranges, and it can smooth the output in 4 stages depending on the need (see attached Excel in case of questions about the physical relations). The whole design has been simulated by LT spice, the files are attached as well. ps. Sorry for the English-German-Mix in some documents but there was no time to translate everything into English until now - deepL or ChatGPT are for sure some good helpers now to translate ;-)