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.
Bad advice, and technically incorrect.
I too have Model 87 and a Model 8060A along with two Tek Scopes a couple of True RMS clamps and all of them use rechargeables. Now I must admit that I do keep a spare rechargeable in every case and I used these instruments
*alot* ( now retired ). My batteries would require a recharge about once a year and I could even recharge them with my inverter in my truck (fodder for another discussion). I can't say I ever got the life out of a 9V that you did (Duracell) and I always shut the meter off when I wasn't using it and have always been surprised the switch didn't wear out...So now you got the rest of the story....but hey...we all have different use patterns and experiences.......take care Dick, Ross
Actually I think the OP probably had a cheap instrument and never gave us a make/model....so hard to say how it would react to rechargeables but if the meter was cheap....it shouldn't make much difference since accuracy would not be an issue with such an instrument.... :>) Ross
Very possible...I will check the site myself....might be one of those situations where we are both correct by situation....not particularly important as long as our fine meters get the job done...and fine they are...take care Dick, Ross
I have a number of portable scopes and meters and have always used rechargeables with no problems and that was on meters I used to calibrate to .001 volts....I'm with you...they work just fine...Ross
You're right. It would just be an unnecessary expense.
Dick
Agreed. The Fluke 87 is one of the best investments in test gear that I ever made.
Dick
I have an old led display Fluke (Model 8030A) that uses 4 NiCads. You leave it plugged in when in when possible.
In alt.home.repair on Sat, 26 Feb 2005 17:46:33 -0500 "Ross Mac" posted:
I believe accuracy should be independent of whether the battery is fully charged or not. They set it up so the measurement is in proportion to a known resistance, so it should read correctly at any battery voltage. (although eventually the battery is too weak to move the needle or power the lcd's.)
BTW, everyone mentions alkaline batteries, but one of my digital meters requires a 9-volt carbon zinc battery. An alkaline battery won't fit in the space provided. (Unlike C, D, AA, and AAA batteries,
9 volt batteries are different in size between carbon-zinc and alkaline.)Meirman
-- If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary.
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.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
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
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.
My math error...E=IR 60PVDC/47Kohms = 1.2ma or so....The incorrect charging rate for a rechargeable.
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....
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!
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
Huh?
Incorrect, eh? :-)
Who's talking about recharging?
Pity.
I just measured a Craftsman digital VOM... 9 V at 1.54 mA.
Pity. That's "tails," BTW.
Nick
Kind of the response I expected....no answers just juvenile quips......PLONK......
The majority of analog multimeters only need the battery to use it as an ohm meter. If only reading voltage, unless it is a transistorized (extremely high impedence) unit the battery is not required.
That might be an Insteon/X10 interface PIC...
The data sheet says it uses about 100 nanoamps at 3 V in sleep mode and
12 microamps at 32 kHz. If it's awake 1% of the time, say 1 second out of 100, when it talks to a central controller, it would need 0.99x0.1+0.01x12 = 0.22 microamps. Q = 340C coulombs and I = 60Q = 0.22x10^-6 amps makes C = 10 pF, theoretically-speaking :-)If we needed more power and worried about overcharging the 2 AAAs, we might use the PIC to measure the voltage and only enable the charge pump as needed.
Nick
Measuring resistance.
Very true. The really cheap meters will say something like 2 Kohm / volt or 3 K ohm / volt on the face. A better quality one will say something like 20K ohm / volt. These ratings are usually based on 1 milliamp giving full scale deflection of the needle. The batteries for resistance readings only.
It was a pain trying to measure voltages across very high resistances. The meter would be in parallel with the resistance and completely mess up the real values.
Getting my first Field Effect Transistor powered meter was a reall blessing. It had something like 2 MEG ohms / volt sensitivity. Most of the digital stuff now probably has 10 or 20 Meg ohms / volt. In some cases that's no good. With almost no loading on a circuit/wire you can get voltages seemingly appearing out of nowhere, giving rise to much head scratching.
mike
You would also need the battery to test Diodes and transitors.
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