Advice on Powering a LED using a CR2032 battery

[Cycloner]

^ was that a new battery? or one that came with your LCD?

hmm. So what should I take from all of this? Is my volt meter working properly? Is it just the batteries that don't give me consistent values?

 

[gophert]

Did you change the battery with a known good battery?

 

[Cycloner]

Do you mean a fresh battery in my Volt Meter? NO I haven't
I just tested a 5.5v Power supply and I get a reading of 5.63v with my meter. So that is a 0.13 difference.
Does that make sense? That is within the +-0.05% range of my voltmeter specification?

 

[gophert]

Yes, a meter that shows inconsistent readings is usually because of a low battery. Measuring a battery that is not connected to anything should have a consistent voltage. There is no logical reason for a battery's voltage to move up or down unless you have a battery with a liquid electrolyte (but you are not measuring a battery with a liquid electrolyte) so, most likely, your meter is suffering from a low battery.

 

[Visitor]

hmm. So what should I take from all of this? Is my volt meter working properly? Is it just the batteries that don't give me consistent values?

[Most*] batteries don't put out a constant voltage over their lifetime. The curve belong shows the discharge characteristics of a CR2032 cell under a small load, but even with no load, the battery will show a similar pattern. Therefore, a battery is not a very good source to check a meter. A "good" battery will read between 2.8 - 3.1 volts, so if your meter reads in this range, it should be fine.

*Some types of batteries like the mercury cells that used to be used as voltage references in meters have extremely flat discharge curves – the voltage is almost constant until the battery is dead. They are not longer available because of environmental and health-safety concerns.

 

[gophert]

Therefore, a battery is not a very good source to check a meter. A "good" battery will read between 2.8 - 3.1 volts, so if your meter reads in this range, it should be fine.

Besides the contradictory information from Visitor, if your meter's readings are jumping around when measuring the voltage of a single battery, you should check your meter's battery, and check if your meter's cables are properly connected and conduct (ohms value on meter). From the battery discharge chart posted by Visitor, you'll see that a battery's voltage doesn't jump up and down over time when it is only connected to your meter probes.

 

[Visitor]

Besides the contradictory information from Visitor.....

Please do explain what that information would be.

And as far as I recall, nowhere in this thread has the OP mentioned meter readings jumping around. I believe the discussion has centered around the meter reading differing from the nominal battery voltage. And just for the record, I had already commented that low batteries in a DVM may result in erroneous readings even before a low battery is indicated.

I do so look forward to your explanation regarding my "contradictory infomation".

 

[gophert]

Please do explain what that information would be.

I do so look forward to your explanation regarding my "contradictory infomation"

Ha, I quoted part of your post for a reason - did you read what I quoted?
In the first quoted sentance, you said a battery is not a good source to check a meter. The next sentence you

And just for the record, I had already commented that low batteries in a DVM may result in erroneous readings even before a low battery is indicated.

And then you got distracted and forgot to follow up and remind the OP that he never answered or didn't understand. For the record", you get zero credit.

special note for you - My Tech support team tells customers how to solve problems all the time. But they don't get credit for solving a problem simply because they were first blurt out an answer. They get the brownie points for getting the customer to trust their advice, listen to their words and implement the recommended corrective procedure.

 

[Cycloner]

And as far as I recall, nowhere in this thread has the OP mentioned meter readings jumping around. I believe the discussion has centered around the meter reading differing from the nominal battery voltage. And just for the record, I had already commented that low batteries in a DVM may result in erroneous readings even before a low battery is indicated.

That is correct. The readings don't "jump" around. They just differ from what they say on the battery it's self.
I will try a new battery in the meter when I get the chance.

 

[Cycloner]

I put in a new Duracell 9v battery in the Volt Meter and I get the same readings as before.
Not sure how to test the meter...

 

[Visitor]

Once again, the voltage specified for a battery is the nominal voltage. The actual voltage of a battery varies with use and age. If the meter is reading approximately the nominal voltage (see the graph I posted above), it should be ok. This is as much as you can determine with a battery. It sounds like your meter is fine.

If you want to verify your meter meets the published specs, you need some kind of voltage reference.

 

[Cycloner]

ok. Thanks for the feedback and suggestions.
-Chris