Today, an LED voltmeter arrived. That means that I now have a green one, a yellow one and a red one. I wanted to see which would be most readable in sunlight.
It turns out that in direct sunlight, none of them are readable. But when I took them into increasing amounts of shade, the red one was the most readable, followed by the yellow, with the green one being pretty bad. That slightly surprised me, because green is the best colour for human eyes. But experiments don't lie.
Then I thought, hmm, how about an LCD? So I've ordered an LCD voltmeter, that can display 18 to 80 volts. I'm thinking that this will work in even the brightest sunlight.
I also ordered a 3.5 inch monitor. I'm planning to use it for a Raspberry Pi display, to replace the LED-array that doesn't work too well. The Pi has a composite output, which will drive the display nicely.