PV showing 0.15v without switch depressed

[Scottes]

I got a new commercial PV the other day and it had a problem. When testing with my cheap-... multi-meter, I held the probes against the atomizer connection to read the volts. I wanted to see if they changed when I hit the button, that's all. I understand about testing voltage under load, but I was simply testing continuity using the DC volts setting.

Then I noticed at one point that I was reading 0.15 volts but didn't have the button pressed. When pressing the button it went much higher, let go of the button and it went down to 0.15.

This was very consistent, and tested 3 times. Probes not touching anything: 0. Probes touching each other: 0. Probes touching atomizer connector: 0.15. With button pressed: 4.something.

This kind seems like a short, but 0.15 volts? I would expect full voltage with a short - among other problems.


I then tested a few other commercial PVs, and found another that consistently read 0.2 volts, and three others that read 0. Every time.


Any ideas here? Problem PVs or just a consistent weirdness from a cheap-... multi-meter?

 

[Shreck]

stray voltage. I doubt its a short or it would be different things than that.. you would get either nothing or more.. Thats what I think anywho!!

 

[Scottes]

"stray voltage" ??? Sounds like a "small short" to me.


Sorry, I guess that I don't understand the term "stray voltage". Could you explain? More importantly, is this anything to worry about on any level?

 

[NickJuice]

I had never heard that term used before...but here an explaination

What Causes Stray Voltage? - Bass Associates Inc.

 

[Scottbee]

No.. it's nothing to worry about. There is circuitry on the other side of those connections! There are MOSFET transistors that produce the current for the atomizer, and there are "sensing" electronics that spring to life when the charger is hooked up. These electronics allow a small amount of "quiescent current" to flow, and will therefore register a small voltage on most meters. And the amount of voltage that you see is largely a function of the type of meter that you have.

So... in short.... don't worry about it! If your battery was actually just a "battery and a mechanical switch", you wouldn't see that voltage. But they are far more complicated than that!

 

[Scottes]

Hmmm. But why did only 2 out of 5 PVs show this phenomenon? Although I've forgotten which ones did what, so I don't know if they were 3.7, l 7.4 or 6.0, or 5-volt models. One was a 5v, the others I forget which.

 

[Scottbee]

"mods" that have a mechanical switch (and no MOSFET circuitry, etc..) should show 0 volts at the atty connection. But very sensitive meters (digital types...) may still show some small voltage (which will usually fluctuate). This voltage can be coming from YOU (you are a big antennae and you pick up all kinds of induced voltage from fluorescent lights and other devices) or other stray sources.

PV's that have vacuum switches, Hall Effect switches, charging circuitry, and low current manual switches that are driving MOSFET transistors will typically show some voltage at the connector at all times.

 

[Scottes]

Thanks Scott. No worries, and too frickin' complicated for me to continue researching. Thanks!

 

[Shreck]

Thanks Scottbee, guess I should have gave more of an explanation of what I was thinking..
If it was a short it would read much higher on your meter. I dont know if there is a such thing as a "small" short..