Using DC Voltage Display Modules in Projects — Accuracy, Wiring, and Tips

The good ones, like the kind that Datel (Murata) sells cost more, but they perform well within the datasheet specifications for reasonable ambient temperatures. Some units have an externally available pot for calibration purposes.

Most panel meter applications are usually an indication, not for precise measurements anyways. There are externally powered units, as well as self-powered units. I never needed to add any additional filtering for any of my applications. The meter had whatever filtering to ensure the display was 'human readable', e.g. reasonably slow refresh rates, and some appropriate low-pass filtering. Again, supply drop errors when using decent sized wires is so far down in the noise, it's not even worth worrying about when it is a process indication only. If you're using a 24-bit DAQ, then we might start worry about that stuff.

Current draw is a function of the meter display. LED's are going to take upwards of 50mA and LCD display type units may only need a handful of milliamps. For battery/solar applications, my preference would be for the LCD display panel meters because their power consumption is so much lower.

As for drift or stability, those issues are also down in the noise for a panel meter.

If you're buying some unknown brand off of Amazon, you will have to do your own assessment. And there is no guarantee that if you order some more a week later, that those will perform anything like the first ones you bought because those units may be a different design and/or manufacturer from the first ones.

I have used single and dual scale to monitor current and voltage on solar setups as well as battery charging from supply voltage PSU.

A check with a Fluke 87 has shown them to be close to the displayed value, within a few 100dredth of the Fluke value.

If you have a good quality meter, a Fluke if you can afford one, you can write a correction figure onto the panel.

Some I have, do have adjustments, others not and the current shunts seem to be accurate enough. The takeoffs from the shunts are separate to the main current terminal though I sometimes only measure up to 200 amps which I compare with a DC clamp on meter.

AC I use current transformers and clamp on meter to feed AC meters.

Regarding these small panel meters, can any body advise any links for altering them to read down to zero volts the self powered ones usually stop at 60 volts.

Sounds like hacking them open and adding the capability for an external source. If you are looking to measure down to zero volts, then you might want one of these:

muRata Part Number: DMR35-ACV2-AC1-R

It does require a separate AC power source.