This topic comes round from time to time (every Leap Year?) and clearly interests quite a few forum members, myself included, but given that we're hobbyists, in my case for the most part restoring vintage equipment which used 10% or even 20% tolerance components, designed to operate on mains power supplies with a voltage input commonly ranging from 220V - 260V, 40 - 100Hz, this striving for accuracy (other than for academic rather than practical reasons), certainly takes us into the 'Volts Nut' arena referred to by Mark in the original thread. See:
https://lists.febo.com/mailman/listi...lists.febo.com
Sure, in a laboratory or sophisticated precision electronic equipment design, construction, testing and repair,or simply for academic interest, but on an upturned chassis of a 1950s domestic radio? I don't think so.
The original thread ran from Jan 2016 - May 2016, and had 112 posts.
In post 5 of that thread, I mentioned that as a compulsive home-brewer, I'd built the 10V Voltage Reference which appeared in Everyday Practical Electronics in June 2011, based on the AD588AQ IC. That IC (.06% accuracy) must have been much cheaper back then as it's now £37.50 and I wouldn't give it a second glance. It was useful and reassuring to check the analogue and digital meters at that time (and since), the most expensive of which was a Toolzone, EL060, which cost me a tenner, the cheapest of which were Maplin 'two for a fiver'. They were all either spot on 10V or no more than 2% or so out.
In post 11 of the original thread, Jeremy (Pamphonica) pointed to a ready made voltage reference available on ebay described as: 'AD584 4 Channel 2.5V/7.5V/5V/10V High Precision Voltage Reference Module'. It's still available at £14.04 post free - less than half the current price of the AD588AQ IC that I used in the EPE 10V Voltage Reference I built.
https://www.ebay.co.uk/c/581937500
Other than the interest and enjoyment of home-brewing, such an off-the-shelf Voltage Reference does blow the cost/benefit argument out of the water. But that said, if cost/benefit was the only criteria, we wouldn't be restoring old radios, the costs of which often far exceeds the monetary value of the radio. (Think DAC90A). All hobbies cost money - that's the price we pay for the enjoyment we derive.
Of course, all that a Voltage Reference will do is to give an indication of accuracy of a meter on the DC Volts ranges, but if we want to check the accuracy of the resistance ranges, we can of course do that with close tolerance resistors. Even 0.1% accuracy resistors are available cheaply:
https://uk.rs-online.com/web/c/?sra=...1%25+resistors
If we have a variable voltage power supply (I do) having checked that my meter voltage range is accurate, I can set the output of the power supply to exactly 10 Volts, then with the meter on the mA range, can connect say a 100 Ohm resistor across the power supply with the meter in series. From Ohms Law, I can expect to see 10/100 - 0.1A (100mA). If I substitute the 100 Ohm resistor for 1,000 Ohms, I can expect the meter to read 10/1000 - .01A (10uA), and so on.
Really, as a hobbyist, for all practical purposes, that's good enough for me.
I'm an old guy restoring radios in a garden shed - I'm not putting rockets into space!
The most alarming thing to me about the pics below has nothing to do with measuring Voltage, but the inability of my brain to accurately calculate elapsed time since past events. It's surreal, and more than a little scary, that eleven years has elapsed since I built that, but it seems like last week.
