I hope this is the right SE, otherwise I might post it on electrical.
I am searching for a voltmeter with a digital output, either RS232 or USB. The ones I came around are very costly for my purpose.
This is what I do now: To measure the voltage of a lead acid battery I use a Raspberry Pi with a MCP3208 ADC and some resistors. It works, but it is a bit of an overkill for such a simple task in my opinion.
The search term "usb voltmeter" leads mostly to USB adapters which show the voltage/current of an attached USB device. Which is not what I want or need.
I don't want to pay more than 50 €, as you can get the RPi for less.
Although not critical, a small device would be preferred.