I'll embarrass myself with this one, but so what...

Just got this little hobbyist's pocket analog multimeter, and it has a slot
for 1 AAA battery, currently empty. The manual only mentions it and doesn't
say why is the battery needed. When I connect the probes to test the power,
the needle deflects, correctly indicating voltage/resistance, once again -
without the battery present. So what is the battery for then?

"Newbie" wrote in message
.. .
I'll embarrass myself with this one, but so what...

Just got this little hobbyist's pocket analog multimeter, and it has a
slot
for 1 AAA battery, currently empty. The manual only mentions it and
doesn't
say why is the battery needed. When I connect the probes to test the
power,
the needle deflects, correctly indicating voltage/resistance, once again -
without the battery present. So what is the battery for then?

It's needed to measure resistance (ohms).
--
Peace,
BobJ

Subject: Why does Analog Multimeter need AAA Batery
Newsgroup: alt.home.repair
= Newbie = wrote:

I'll embarrass myself with this one, but so what...

Just got this little hobbyist's pocket analog multimeter, and it has a slot
for 1 AAA battery, currently empty. The manual only mentions it and doesn't
say why is the battery needed. When I connect the probes to test the power,
the needle deflects, correctly indicating voltage/resistance, once again -
without the battery present. So what is the battery for then?



It would be needed to measure resistance. How on Earth are you measuring
resistance without a voltage source? Tell the truth... Did you REALLY measure
a resistor?




--

-Graham

Remove the snails to email

The battery is necessary when measuring resistance. If you put the meter
on the resistance scale and touch the probe tips together, the meter
should deflect to the zero ohms end if the battery is installed.

Newbie wrote:

I'll embarrass myself with this one, but so what...

Just got this little hobbyist's pocket analog multimeter, and it has a slot
for 1 AAA battery, currently empty. The manual only mentions it and doesn't
say why is the battery needed. When I connect the probes to test the power,
the needle deflects, correctly indicating voltage/resistance, once again -
without the battery present. So what is the battery for then?

"Newbie" wrote in message
.. .
I'll embarrass myself with this one, but so what...

Just got this little hobbyist's pocket analog multimeter, and it has a
slot
for 1 AAA battery, currently empty. The manual only mentions it and
doesn't
say why is the battery needed. When I connect the probes to test the
power,
the needle deflects, correctly indicating voltage/resistance, once again -
without the battery present. So what is the battery for then?


The only test/s that a simple analog meter (with a needle or moving finger)
should require a battery for is continuity/resistance tests.
You are correct; an analog meter will measure external sources of electrical
voltage and/or current without the battery.
However when you desire to measure an inanimate or other wise unpowered
circuit or item the source of electricity for that measurement is the small
battery inside the meter.
By the way don't try to measure any external voltage or current with the
meter set to "Ohms" or "Resistance" ranges!
For an example; holding a bulb/lamp in your hand you connect the test leads
(set to ohms/continuity etc.) to a lamp/bulb in attempt to find out if it's
'blown' or OK?
You will not get any reading at all unless that battery is in place!
That makes sense of course because current will not flow without a source of
voltage.
BTW is this a troll?
If not suggest that a quick self paced course on basic Ohm's Law will assist
advantageous use of the meter and perhaps minimize the chances of "Blowing
the sh**" out of it! Which we have all done at one time or another.
Also read the little book that should come with the meter. There are some
applications where such a small analog meter can do better job than a more
sophisticated more sensitive one!

"Newbie" wrote in message

Just got this little hobbyist's pocket analog multimeter, and
it has a slot for 1 AAA battery... what is the battery for then?

It's an annoyance. Take the meter out of a drawer, and the battery's dead.
You might add a diode and series 47K ohm resistor to the switch contact used
to measure 120 VAC and leave the meter leads plugged into a wall socket to
monitor house voltage and keep the battery charged.

Nick

"It's an annoyance. Take the meter out of a drawer, and the battery's
dead.
You might add a diode and series 47K ohm resistor to the switch contact
used
to measure 120 VAC and leave the meter leads plugged into a wall socket
to
monitor house voltage and keep the battery charged. "

Another example of practical advice from pointed head academia.

nick,

I don't follow this. When the meter is set to measure 120 VAC the battery
is not in the circuit and can not be charged, I think. Also can you safely
charge non rechargeable batteries? This sounds like very bad advice,
especially for a newbie.

Dave M.

On Sat, 26 Feb 2005 16:08:45 GMT, "David Martel"
wrote:

nick,

I don't follow this. When the meter is set to measure 120 VAC the battery
is not in the circuit and can not be charged, I think. Also can you safely
charge non rechargeable batteries? This sounds like very bad advice,
especially for a newbie.

Dave M.


You don't want to fool with a rechargeable battery in an analog VOM.
For that matter, you don't want one in a digital voltmeter either.
Alkaline batteries have a shelf life of several years. As others have
already pointed out, the only thing the battery is for is in measuring
resistance. This reading depends upon measuring the current flow
through resistors in the meter. If there is no battery, there will be
no current flow. The meter would work fine for all other measurements
because they generate their own source of power to operate the meter.

Dick

"Dick" LeadWinger wrote in message
...
On Sat, 26 Feb 2005 16:08:45 GMT, "David Martel"
wrote:

nick,

I don't follow this. When the meter is set to measure 120 VAC the
battery
is not in the circuit and can not be charged, I think. Also can you safely
charge non rechargeable batteries? This sounds like very bad advice,
especially for a newbie.

Dave M.


You don't want to fool with a rechargeable battery in an analog VOM.
For that matter, you don't want one in a digital voltmeter either.
Alkaline batteries have a shelf life of several years. As others have
already pointed out, the only thing the battery is for is in measuring
resistance. This reading depends upon measuring the current flow
through resistors in the meter. If there is no battery, there will be
no current flow. The meter would work fine for all other measurements
because they generate their own source of power to operate the meter.

Dick

Why wouldn't you use a rechargeable battery in a meter? I've had one in my
$400 Fluke DMM, sent out for repair and calibration and it came back with
the rechargeable still in place. Apparently they didn't have a problem with
it nor have I for at least 15+ years. Just curious Dick....take care, Ross

wrote:
It's an annoyance. Take the meter out of a drawer, and the battery's
dead. You might add a diode and series 47K ohm resistor to the switch
contact used to measure 120 VAC and leave the meter leads plugged
into a wall socket to monitor house voltage and keep the battery
charged.

Bad advice, and technically incorrect.

wrote in message
...
"Newbie" wrote in message

Just got this little hobbyist's pocket analog multimeter, and
it has a slot for 1 AAA battery... what is the battery for then?

It's an annoyance. Take the meter out of a drawer, and the battery's dead.
You might add a diode and series 47K ohm resistor to the switch contact
used
to measure 120 VAC and leave the meter leads plugged into a wall socket to
monitor house voltage and keep the battery charged.

Nick

What's wrong with a spare rechargable battery and a cheap charger.
The way I see it you are suggesting a 1.5 volt battery be charged at a rate
of 25 ma at 60 volts pulsating DC? Or did you mean 1.5V zener diode? If you
were to use a *standard diode* you would be limited to about a half a volt
and the battery would never charge. I think you also failed to mention the
battery would have to be across only the diode. In any event it would still
be a poor charger........Ross

Ross Mac wrote:

You might add a diode and series 47K ohm resistor to the switch contact
used to measure 120 VAC and leave the meter leads plugged into a wall
socket to monitor house voltage and keep the battery charged.

What's wrong with a spare rechargable battery and a cheap charger.

Well, that way you need two batteries and a charger, and rechargable batteries
are more expensive than plain carbon zinc, and the meter may not work well on
1.2 vs 1.5 V, and this arrangement won't monitor house voltage, and it takes
more human attention, and it's less fun.

The way I see it you are suggesting a 1.5 volt battery be charged at a rate
of 25 ma at 60 volts pulsating DC?

More like 1 mA, altho that's too much for an Eveready 1212 AAA with a 540 mAh
capacity that loses 10% of its energy over a year. That only needs 0.10x540
= 54 mAh over a year, or about 6 microamps on a continuous basis, if the meter
is never used for anything else, but the movement might require another 100
microamps. And why waste power in that resistor, vs a charge pump like this,
viewed in a fixed font?

- C
| \ | | | 1.5 V
------------------| |---------------|--------------------
. | | | | |
120V . --- ---
. ^ -
------------ | |
| | |
| / | | |
- --- --- ---
- _ -

Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads.
The battery would be a fine smoother and voltage regulator. Harbor Freight
stores sell $2.99 digital multimeters. Maybe they need less than 100 uA.

My flashlight plugs into the wall. Very convenient, because I know where to
find it and don't have to change batteries. My CO and barn heat detectors
work that way too, by design, with audible and remote X10 alarms and "non-
rechargable" batteries that rarely need changing. I hate changing batteries.
I lose my cheap Casio watches with 7 year Li batteries before they go dead.

Nick

wrote:

- C
| \ | | | 1.5 V
------------------| |---------------|--------------------
. | | | | |
120V . --- ---
. ^ -
------------ | |
| | |
| / | | |
- --- --- ---
- _ -

Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads.

Oops. Q = 340C makes C = 0.0047, or two 0.01s in series in case one shorts.

Or a 20 mW LimeLight, with less power. What does it take to power a 648A PIC?

Nick

wrote in message
...
Ross Mac wrote:

You might add a diode and series 47K ohm resistor to the switch contact
used to measure 120 VAC and leave the meter leads plugged into a wall
socket to monitor house voltage and keep the battery charged.

What's wrong with a spare rechargable battery and a cheap charger.

Well, that way you need two batteries and a charger, and rechargable
batteries
are more expensive than plain carbon zinc, and the meter may not work well
on
1.2 vs 1.5 V, and this arrangement won't monitor house voltage, and it
takes
more human attention, and it's less fun.


Absolutely incorrect. That is not how a meter works.
And anyhow....a spare battery and a charger???....That is not expensive....
Not trying to fire ya up here but those are the facts.

The way I see it you are suggesting a 1.5 volt battery be charged at a
rate
of 25 ma at 60 volts pulsating DC?


My math error...E=IR 60PVDC/47Kohms = 1.2ma or so....The incorrect charging
rate for a rechargeable.

that's too much for an Eveready 1212 AAA with a 540 mAh
capacity that loses 10% of its energy over a year. That only needs
0.10x540

Those batteries are normally referred to as "Puny Duty" and typically never
make it to 10 recharges...
I don't think this is a good recomendation to the NG....

= 54 mAh over a year, or about 6 microamps on a continuous basis, if the
meter
is never used for anything else, but the movement might require another
100
microamps. And why waste power in that resistor, vs a charge pump like
this,
viewed in a fixed font?

- C
| \ | | | 1.5 V
------------------| |---------------|--------------------
. | | | | |
120V . --- ---
. ^ -
------------ | |
| | |
| / | | |
- --- --- ---
- _ -

Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01
microfarads.
The battery would be a fine smoother and voltage regulator. Harbor Freight
stores sell $2.99 digital multimeters. Maybe they need less than 100 uA.

I cannot make heads nor tales out of your schematic, fixed font or not, but
it appears we now have a capacitor in the circuit...what happened to the
"diode and resistor" and you still need a regulator since you still have 60
volts across a 1.5 volt battery.
And please no, no....not that doorstop 3 buck meter...a good set of leads
will cost you more than that thing. That meter is more likely to get you
into more trouble than it ever gets you out of. That "THING" would only be
good for very crude troubleshooting.

This post is beginning to smell of TROLL.....well maybe not....but the bait
and switch characteristics are there!

My flashlight plugs into the wall. Very convenient, because I know where
to
find it and don't have to change batteries. My CO and barn heat detectors
work that way too, by design, with audible and remote X10 alarms and "non-
rechargable" batteries that rarely need changing. I hate changing
batteries.
I lose my cheap Casio watches with 7 year Li batteries before they go
dead.

Nick

As for connectiong the active and passive circuits in the meter....I want to
be there when you try to measure the 240vac coming into the house and you
put 120pvdc across that battery with a camera to catch the absolute look of
surprise......Ross

wrote in message
...
"Newbie" wrote in message

Just got this little hobbyist's pocket analog multimeter, and
it has a slot for 1 AAA battery... what is the battery for then?

It's an annoyance. Take the meter out of a drawer, and the battery's dead.
You might add a diode and series 47K ohm resistor to the switch contact
used
to measure 120 VAC and leave the meter leads plugged into a wall socket to
monitor house voltage and keep the battery charged.

Nick

Basis of an idea there; as you suggest you'd have to modify the circuit a
bit!
Probably not worth while because even the simplest kind of primary cell is
so cheap (25 to 50 cents?) and available and last so long. Prob. not worth
doing it to a simple $6 to $15 'pocket style multimeter'?
Rechargeable for a 'digital' display meter might be OK; especially if I tend
to leave ours with its LCD display switched on after use!!!!!
In a simple analog meter, the battery, which powers only the
resistance/continuity scales, is so little used that it will last its shelf
life and then some. And since meters tend to be stored in reasonable
environment; unless it's in my vehicle glove box and the battery freezes,
the battery will normally die of old age rather than use?
In a typical analog meter, the battery supplies, and only momentarily,
something of the order of one half milliamp (that's one 2000th of one amp
for only the few seconds of testing!).
So if it does not leak or rust away the battery will have potential for
years!
I've seen one or two cells that were 20 years old and still had enough
potential to fully deflect the meter. After all the batteries in our smoke
detectors last a year and they 'are' providing a 'constant' small drain.
Keeping a spare pack of the cheapest batteries available a good idea. Also,
in effect an analog meter tests its own battery; every time you check FSD
for zero ohms; right?
BTW on the subject of small cell batteries, including those 9v 'Transistor'
style, one of the most useful and productive 'gadgets' is one of those
R.Shack battery testers. Sometimes on sale for half price at around $5 to
$8.
Being congenitally unable to 'not tinker' with anything! Have started to
modify our little battery tester, hopefully to enable one hand testing of
the continuity of say fuses and/or lamps! Despite that we have several
multi-meters; but justify that a combined battery/fuse/lamp tester would
result in one less thing (multimeter) to carry around? :-)
Suggestions: When you chuck out an old shaver save the zipped and slightly
soft padded container, often just right size for a multimeter! By then the
cardboard box the meter came in from Taiwan, China or Mexico will have
crumbled. And; those soft padded/insulated fabric school lunch 'boxes' are
an excellent container for a test instrument, test leads, low wattage AC
bulb for checking mains supply, short extension cord, neon tester etc. and a
couple of small hand tools. All in one package; so when your favourite Aunt
Ida phones and says her lights are blinking, again, and she also needs a new
bulb in her flashlight, just grab it and go.
Have fun out there!

Thanks Terry, and everyone else for your help. In retrospect it appears sooo
obvious that resistance measurement requires some kind of power source...

Thanks again everyone....


"Terry" wrote in message
...
|
| "Newbie" wrote in message
| .. .
| I'll embarrass myself with this one, but so what...
|
| Just got this little hobbyist's pocket analog multimeter, and it has a
| slot
| for 1 AAA battery, currently empty. The manual only mentions it and
| doesn't
| say why is the battery needed. When I connect the probes to test the
| power,
| the needle deflects, correctly indicating voltage/resistance, once
again -
| without the battery present. So what is the battery for then?
|
|
| The only test/s that a simple analog meter (with a needle or moving
finger)
| should require a battery for is continuity/resistance tests.
| You are correct; an analog meter will measure external sources of
electrical
| voltage and/or current without the battery.
| However when you desire to measure an inanimate or other wise unpowered
| circuit or item the source of electricity for that measurement is the
small
| battery inside the meter.
| By the way don't try to measure any external voltage or current with the
| meter set to "Ohms" or "Resistance" ranges!
| For an example; holding a bulb/lamp in your hand you connect the test
leads
| (set to ohms/continuity etc.) to a lamp/bulb in attempt to find out if
it's
| 'blown' or OK?
| You will not get any reading at all unless that battery is in place!
| That makes sense of course because current will not flow without a source
of
| voltage.
| BTW is this a troll?
| If not suggest that a quick self paced course on basic Ohm's Law will
assist
| advantageous use of the meter and perhaps minimize the chances of "Blowing
| the sh**" out of it! Which we have all done at one time or another.
| Also read the little book that should come with the meter. There are some
| applications where such a small analog meter can do better job than a more
| sophisticated more sensitive one!
|
|

In alt.home.repair on Sat, 26 Feb 2005 03:10:30 -0330 "Terry"
posted:

There are some
applications where such a small analog meter can do better job than a more
sophisticated more sensitive one!

One thing is allowing you to watch a capacitor charge. Eventually the
needle reaches the resistance of the circuit, not counting the
capacitance.

Meirman
--
If emailing, please let me know whether
or not you are posting the same letter.
Change domain to erols.com, if necessary.

Hi Newbie, hope you are having a nice day

On 25-Feb-05 At About 13:38:17, Newbie wrote to All
Subject: Why does Analog Multimeter need AAA Batery

N From: "Newbie"

N I'll embarrass myself with this one, but so what...

N Just got this little hobbyist's pocket analog multimeter, and it has
N a slot for 1 AAA battery, currently empty. The manual only mentions
N it and doesn't say why is the battery needed. When I connect the
N probes to test the power, the needle deflects, correctly indicating
N voltage/resistance, once again -without the battery present.
N So what is the battery for then?

It is needed for the resistance ( Ohm) readings.


-= HvacTech2 =-


... **FLASH** Eveready Bunny arrested, charged with battery.

___ TagDude 0.92á+[DM]
++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++
spam protection measure, Please remove the 33 to send e-mail

HvacTech2 wrote:



.. **FLASH** Eveready Bunny arrested, charged with battery.

***** Sentenced to 2-4 years in a dry cell.

Jeff


--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

In article ,
Newbies wrote:
I'll embarrass myself with this one, but so what...

Just got this little hobbyist's pocket analog multimeter, and it has a slot
for 1 AAA battery, currently empty. The manual only mentions it and doesn't
say why is the battery needed. When I connect the probes to test the power,
the needle deflects, correctly indicating voltage/resistance, once again -
without the battery present. So what is the battery for then?



Measuring resistance.


--

Larry Wasserman Baltimore, Maryland

You would also need the battery to test Diodes and transitors.