If Jay_Diddy_B did know the Silicon Chip Design of 2011, it would be fine if he had presented his project as an improvement of this earlier design.
But, anyway, this new version has a lot of features:
- using +/- 2.5V power supply instead of +/-5V, so it can be powered by a single 9V battery.
- fully protected against charged capacitors.
- few components
- single sided board project.
But i don't agree with some ideas:
- 4W is nonsense as this project is not a high precision tool....it's intended for diagnose and repair.
Using Kelvin probes is not practical at all.
- need a zero ajust pot for compensating both offset and resistance of the test probes. With such a zeroing pot, there is no more need of a multimeter with relative function, nor to choose a low offset op amp. You short circuits the probes and ajust the pot for 0V reading.
- I would prefer to have two frequencies: 100Khz and 10Khz as 100Khz seems a little high for big capacitors.
- Actual range is 100mV = 1R....better to have 2 ranges, also 1V = 1R for easier reading and greater accuracy.
- in my opinion, should use only very easy to buy components...TLC555 (cmos version of 555), 4013, 4066, LM324, 78L05.
I also found an error in this project: there is no ground reference for the inputs of the op amp because there is an isolating capacitor and high resistance values. Inputs are "floating" and are not symetricals compared with ground.
For solving this problem, I added two 10K resistors in parallel with the capacitors C3 and C4 of Jay_Diddy_B schematic.
- A made 2 new versions, the first is allready working very well. I have still to make the board of the second one, but it's not that easy because I want to make a single side board project.