Do inline 510 volt meters have a fundemental flaw?

[UncleChuck]

I usually check voltage under load via a multimeter on the atty posts, but was thinking of picking up one of those inline volt meters for easier readings, but I was a little concerned about something.

Under high current loads, couldn't the meter itself introduce quite a bit of error into the equation (well, quite a bit relative to the tenths of a volt we are looking at?)

If the device introduced a significant amount of resistance into the circuit, this would put less strain on your battery, which means you aren't getting accurate readings. Reason being the total resistance in the circuit is all that matters to the battery, if your atty is .5 and the meter is .2 the battery is only being strained as it would be by a .7 ohm load.

Since we are dealing with tenths of a volt here, doesn't it seem like the resistance of the meter would throw of the readings as to make them pretty useless? Anyone ever compare a good multimeter on the posts, to an inline with everything else the same and see how they compare to each other?

Thanks!

 

[WattWick]

Interesting point. Want to see what comes out of this if anyone has done some testing. Come to think of it... voltage drop with atty AND inline volt meter AND mod doesn't necessarily say much about real world use, or where this drop comes from.

 

[shoggot]

From a very basic engineering standpoint, the internal resistance of the multimeter is likely to be higher than that of the inline - if only because the leads for the multimeter are generally significantly longer than the very short wire run required for the inline meter. I strongly suspect both have some degree of compensation / expectation of internal resistance, and account for it, though.

 

[UncleChuck]

From a very basic engineering standpoint, the internal resistance of the multimeter is likely to be higher than that of the inline - if only because the leads for the multimeter are generally significantly longer than the very short wire run required for the inline meter. I strongly suspect both have some degree of compensation / expectation of internal resistance, and account for it, though.

Makes perfect sense! Hopefully that's the case, I like the idea of using the inlines.

I'm no professional so I'm struggling a bit with theory here, but are the "conditions" of putting multimeter leads on the posts the same "conditions" seen when running through the inlines?

When using a meter on the posts, the atty is directly connected to the mod, with a direct and low resistance connection to the battery. I'm assuming the meter is built basically as an oversized 510-510 converter, with the pos and neg of the original 510 just passing up to the new one in effect, with the meter hanging on reading voltage.

My worry isn't so much with the meter itself, more so with the "extension" that the meter latches on to, if that makes any sense.When using the inlines the full current is passing through the meter and whatever wire and circuit paths inside, is the same true for multimeters on posts?

I was under the impression that when putting a meter on the posts, it was more of a passive reading, and the high current of the build isn't passing through the multimeter and it's leads? In the same way putting the multimeter leads straight on a battery doesn't dump the full current output capability through the multimeter (or else reading battery voltage this way would heat/drain the batteries up quick) putting leads on the posts doesn't put a high current strain on the leads, right?

Where as any connection between the inline meter and the atty will have the full current passing though it at some point, in a manner it wouldn't normally when using the atty directly attached to the mod.

As I said, I'm no professional, so I'm probably doing a bad job of getting across what I'm saying, sorry about that


Thanks for the responses so far!

 

[shoggot]

If I'm following correctly, you're speaking of the difference between using a multimeter on battery + atomizer (let's say a genny) and measuring between positive and negative posts, where you'd normally connect resistance wire, versus using the inline connected directly (more or less) to the batter, without the atomizer being part of the picture (or, stuck inline on the other end of the inline voltmeter).

You -should- see an increased voltage drop when using the multimeter if done that way, since you have the internal resistance of the atomizer body as part of the equation. I suspect (I don't have an inline voltmeter, but have nothing against them, obviously) that if you were to stick the probes into the 510 connector on the battery unit - one on the outer edge, one on the center post - you'd read the same as if you stuck the inline voltmeter on the 510 on the battery unit without an atomizer attached.

a) HTH, b) Hope that made sense (I don't think HTMS is a common acronym...)

 

[UncleChuck]

If I'm following correctly, you're speaking of the difference between using a multimeter on battery + atomizer (let's say a genny) and measuring between positive and negative posts, where you'd normally connect resistance wire, versus using the inline connected directly (more or less) to the batter, without the atomizer being part of the picture (or, stuck inline on the other end of the inline voltmeter).

You -should- see an increased voltage drop when using the multimeter if done that way, since you have the internal resistance of the atomizer body as part of the equation. I suspect (I don't have an inline voltmeter, but have nothing against them, obviously) that if you were to stick the probes into the 510 connector on the battery unit - one on the outer edge, one on the center post - you'd read the same as if you stuck the inline voltmeter on the 510 on the battery unit without an atomizer attached.

a) HTH, b) Hope that made sense (I don't think HTMS is a common acronym...)

Yeah that's basically what i do, just press the probes into the screw heads on the positive and negative terminals with everything put together and ready to vape, then I fire the device with the probes still pressed to the screws and read the voltage.

I'm still thinking whatever wire/connections are used to bridge the connection between the top and bottom 510 might add a bit of resistance, however I just have no idea if it's significant enough to cause any issues.

I might as well pick one up and do a comparison, they aren't terribly expensive. I'll make sure to report back when/if I do so.

Thanks guys!

 

[CloudZ]

I thought about this topic a bit and deduced that the stated concerns should be a non-issue. If whoever designed these inline meters even knows very little about electric circuits, their effect on the battery load through added or reduced resistance should be incredibly tiny. All it takes is a relatively high resistance voltage sensor in parallel, which is just like touching multimeter leads to the coil posts. Any series resistance is what causes voltage drop in our mods, and if these inline meters were wired in series they would simply be measuring the voltage drop across themselves, which is pointless.

So the answer is, of course they use a parallel sensor and should be real-use accurate. This was puzzling me for a while as well, but I think I figured it out. To visualize it, think of two wires connecting your mod to your atty. One wire connects the male/female 510 threads and the other connects the positive pin to the positive post. The volt sensor just bridges between these two wires at some point.

 

[Stosh]

What CloudZ said ^^^ voltage is always measured as a parallel circuit, with the meter having a very high resistance. In a DC circuit this means very little power, volts, amperage or watts are being "used" by the meter, just enough to get a measurement.

Measuring amperage is done with the meter is series with the DC circuit, and the meter is very low resistance as to effect the measurement the least possible.

 

[UncleChuck]

This was puzzling me for a while as well, but I think I figured it out.

I'm glad I wasn't alone I'm no professional, but I'm fairly well versed with this basic type of theory so it was frustrating that I was having a difficult time confidently visualizing it.

Thank you guys very much for your time!