Microcontroller Based Digital Capacitance Meter

Have you guys ever wondered how does capacitance meters work? This project walks you through the process of building your own microcontroller based capacitance meter. It uses a PIC16F628A – this was choosen because of its simplicity and it has built in analog comparators and timer modules. Theory behind the operation of this capmeter (and most capmeters) revolves around the charging time constant – the amount of time it takes for the voltage of a capacitor to reach a certain level (in this project Vin/2) from 0V (no charge at all). This capacitance meter is equipped with a 2×16 liquid crystal display (LCD) that is hooked up into the PIC16F628A’s port B. Regulated power is supplied through a 78l05 voltage regulator (this is added to avoid corrupting the result due to unstable supplies) . Measurement is initiated using a momentary switch that is hooked into RB0 – Just press START and start measuring! Continue reading

High resolution lightweight capacitance meter on PIC

Many capacitance meters limits their resolution to 3 or 4 digits while this one reaches 7 digits. What does it mean? This means that you can measure capacitance more precisely especially when talking about very small capacitors in pF range. Device is built around PIC16F628 microcontroller which also provides its internal comparator for oscillator. Using PIC’s internal comparator makes cap meter very lightweight on schematic. Whole magic happens in comparator circuit where tested cap along with known resistor generates a waveform. Comparator is set to capture high and low signal values at 1/3VDD and 2/3VDD while microcontroller timer counts waveform period. Knowing period it is easy to calculate capacitance value. Cap meter also has a zeroing and calibration functions that helps reaching better precision. Continue reading

Easy to build auto-range capacitance meter

If your multimeter doesn’t measure capacitance or you want to have wide auto-range capacitance measurement capabilities then try this project. Capacitance meter measurement range is quite large (from 5pF up to 2600μF) and of course range is selected automatically.   This capacitance meter like others use charging time measurement technique (τ=RC). Circuit is really simple. There are three buttons used. Two of them are used to calibrate capacitance meter in order to remove stray capacitance. Third button is used to save calibration data to EEPROM memory. You can download assembly source code compile and burn to PIC16F873A microcontroller. I guess this is a nice tool that fits in to collection. Continue reading