Multimeter
Could be a good DIY project. Use an AVR. My multi-meter doesn't seem to measure capacitance very accurately and I don't like that it's powered by a 9V battery.
Features
- Resistance
- Voltage (AC/DC)
- Current
- Frequency
- Capacitance
- Inductance
- Transistor measurements (this would be nice if it could identify type, leads and rating)
This could also have 5V out (I'll need that for the circuit anyway) and some signal generators (just use the PWM on the AVR).
Resistance
This should be easiest because we don't have to worry about frying anything. We put 5V across a voltage divider where one resistor is what we want to measure and the other is known. Measure the voltage in the middle, a bit of math, and get the resistance.
Voltage
I want to be able to measure a wide range of voltage at high precision. Say 0-1000V, without frying the AVR. The AVR has a resolution of 4.88mV
I should be able to accomplish the primary portion of the circuit with a power transistor. Set it up to limit the voltage drop across a resistor to 1 V.