Digital Meter Training Camp

A simple and practical digital meter
incorporates a voltage reference chip. The core of the 431 microcontroller is an operational amplifier (op-amp) that acts as a comparator in the circuit. Internally, the chip has a voltage Vref (approximately 2.5V), which acts on the inverting input of the comparator. The non-inverting input of the comparator receives a voltage input to REF. When this voltage is greater than Vref, the comparator outputs a high level, enabling a transistor and connecting the CATHODE (cathode) and ANODE (anode) terminals. If REF and CATHODE are at the same potential (connected together), the potential at REF is pulled low. When the potential at REF drops below Vref, the comparator outputs a low level, the transistor turns off, and the potential at REF rises back up. When it rises above Vref, the process repeats. Because the hardware response speed is extremely fast, the voltage at REF is almost equal to Vref.