Good point about meters.
Somebody (might have been d) posted a low cost plug in digitial Vac display on here a while back. I'd put it on my Amazon list, but forgot on my last order, I'd intended to get at least one.... These (and other low cost portable meters) aren't precise..... I think of them as similar or slightly better than gauges on a car dash...... they give you an earlier headsup of trouble, and a rough approximation of OK health.
Grab 2 low cost meters, and measure the same AC voltage, not a surprise if they don't exactly agree.
Lesser meters have a tougher time with generators (and some line voltage situations) too..... electrical noise can skew the AC reading.
One of the things you get in a more expensive meter is true-rms readings for AC. Better for reference readings, and can be thought of this way:
The RMS value of an alternating current is also known as its heating value, as it is a voltage which is equivalent to the direct current value that would be required to get the same heating effect. For example, if 120 V AC RMS is applied to a resistive heating element it would heat up by exactly the same amount as if 120 V DC were applied.
True RMS converter - Wikipedia
"AC voltage" presumes a pure sine-wave. True-RMS reading meters do a better job of standardizing AC measurements, given real-world (ie. distorted) signals to deal with.
I expect low-cost meters to not have high initial accuracy, and to drift with temperature. Checking my gen in summer , it could be over +30C ambient, Winter could be -30C.
Long way of saying..... having a low-cost meter at hand (I have several) is useful, and a whole lot better than just wiring up a test lightbulb, but I don't really expect them to agree exactly, one to the other....
Rgds, D.
