I own a semi-professional DMM Rigol DM3058E, but I wound't let it out the laboratory since it's a bit expensive (I paid it 520 euro). So for a crazy project I am considering the purchase of "low cost" DMM, but I need it with a serial RS232 line
- Mastech MS8218 (battery powered)
- Mastech M9803R (230VAC powered)
- Brymen BM857 (battery powered)
look interesting, but they are a bit expensive, ~ 180 .. 250 euro (the Brymen BM857 require a RS232 adapter, so I have already included the 60 euro of cost in the 250 euro)
In my opinion they are not professional but decent multimeters and able to measure more things than what I need: I only need a digital voltmeter with a RS232 line, and I need to measure voltage in the { -24V .. 24V } DC, in three working scales
- 0..100mV (here I need +/-0.25mV of precision)
- 0..10V (here I need +/-10mV of precision)
- 0..100V (here I need +/-100mV of precision)
I am thinking about it, and ... in theory I can use a fast SPI ADC 12bit coupled with some OA, SIL rele' to switch circuits, a MPU to manage measures and digital signal conditioning (interactive-mean? min/max values in a time window?), would it be reasonable? and If yes, what about the protection and analog circuit to interface the probe?
Is there a project to look at as reference, or - better - is there a kit?
Just to consider it makes sense or if I'd better buy something "second hand" on eBay.