0 to 100v Voltage display.. 3 wire ?

[Ypedal]

http://www.newfrog.com/p/three-wires-mini-digital-voltmeter-dc0-100v-blue-light-dc-voltage-meter-49845.html?utm_source=emars&utm_medium=newsletter&utm_campaign=1111newsletterUS2_endoscope

Got this on email spam, what's the 3rd wire for ?... anyone. ?

 

[Gregory]

The voltage regulator (that powers a display and microcontroller?) of the meter can only run up to about 30V.
That is typically the RED wire.

The meter can measure up to 100V on the Yellow or White wire.

 

[amberwolf]

Measuring range:
DC 0-100V
Minimum Input
DC 0V
Maximum Input
DC 100V

Power supply
DC3.0-30V

So one wire ground, one wire meter power, one wire measuring input.

 

[John in CR]

Which can you see better in sunlight, red blue or green? I'd get spendy and put the extra buck on the 5v-120v two wire with the slightly larger red display, no need to power it separately, and you're sure it's DC. The 3 wire units say alternating current in the description.

Then there's also the waterproof units for 4 and change.

 

[amberwolf]

Some discussion on the color thing:
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=40616&p=936240
(anotehr cheap meter thread)

Comes down to...it's really complex. And complicated further by teh fact that not all of the LED colors tend to put out the same amount of light, either. (and even if they did, there's different brands and chip makes and whatnot, and ways of runing the display, that make them brighter or dimmer).

Basically, there's no certain way to tell which would be brighter for a specific brand/model of meter.

But in general, I would guess that Red is probably easier to see until the sun gets too bright, and then you need a hood for it to shade it, and/or a contrast-increasing lens (which is why they often use those red lenses on red LED displays, green on green ones, etc).