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