Digital multimeter

BTW, afaik all meters cheap or expensive, unless maybe it was home-built, have a clever circuit, (whose name I forget. It looks like a 4-sided diamond) , that makes the read-out the same, even when the voltage of the battery inside is going down. When the battery is almost dead (1.3 or 1.4 volts for a nominal 1.5 volt battery) it won't work but if it's 1.47, which might be 80% discharged, the reading should be the same as with a new battery.

Meters don't use much current, so they might work with batteries that don't work in a portable radio with an actual speaker. (radios that drive headphones don't need so much power so I'm not comparing with them.)

I'm sure some people here will take issue with some of this. It's true that my numbers are only educated guesses.

Reply to
micky
Loading thread data ...

I think the problem lies in someone thinking the voltage is really there, and wasting an hour (hours) trying to find out why it's there and get rid of it. Well, the voltage is tthere, but the charge in coulombs is very small. Because there is no load connected to it, it can be high voltage like that. The meter is a load but it 11megohms per volt, so high the charge doesn't get used up. If you were using an analog meter at 20 kilohms per volt, the meter itself would drain away the charge and make the voltage drop to zero.

I didn't realize, never saw any before yesterday, that not only does Amazon have ratings, they have comments on the rating comments. If you look at this conversation about the Fluke 114, that someone recommended,

formatting link
you'll see "3. I believe he mentions the Fluke 115 model, but the 115 lacks the low impedance (Lo-Z) voltage measurement feature which is nice for two reasons: It eliminates weird induced/stray voltages by actually making the source do a little work,[and it automatically selects AC or DC]. This is the best and safest mode to use to verify absence or presence of live power."

This is the first reference I've seen to a digital meter that can do this.

Another guy goes on to cite his meter, that displays the AC and DC voltages at the same time. (Don't worry Jennifer, you'll almost surely never come across this.)

Reply to
micky

I would lower this to Nice to Have. In 45 years, I've measured current 4 or 5 times.

Well, the cute little meters, maybe 1/2 inch thick by 3 x 4 inches, that one can carry in a shirt pocket while viisting friends have permenently attached leads. It's worth it to me so if I'm there for dinnner and they have electrical problems, I can whip out my meter, before my host can even get his from the workshop (if he even has a workshop). This hasn't happened often, actually never, so the leads aren't close to wearing out yet, but like my horse Trigger, I like having it with me.

Reply to
micky

Years ago, Nite Ize had LED conversions for mini mag flash light. They fit nicely into the black and yellow HF head lamp. The one that takes two AA cells. Makes for a good light, with AA cells that last longer than AAA cells. Just have to pull out the bi pin bulb, and break out the provided reflector. Fits nicely into the lamp with the Nite Ize reflector inside the HF plastic lens.

Reply to
Stormin Mormon

Jennifer,

Most cheap digitals work fairly well. Look at the leads. You want robust leads and good probes. I also favor auto-ranging. Spend around $30.

Dave M.

Reply to
David L. Martel

For a Fluke, there is

formatting link
which plugs in between the meter and leads and provides a lower resistance. Probably works with other meters with the same lead spacing and plugs.

Reply to
bud--

A lot of the cost is making the meter safe if you make a mistake on high capacity circuits, as in one of Ralph's posts. A real good idea if you are working in service panels or somewhere other than on the end of a

20A branch circuit.
Reply to
bud--

The Sears insert that came with today's paper shows a combination deal of a digital multimeter and AC voltage probe for $14.99 ("Save $12"); item number is 03482146.

Perce

Reply to
Percival P. Cassidy

The nice fellow works as a millwright on industrial shutdowns so he winds up working nights and when people came on his property and stole his stuff, he decided to put up some wireless IP cameras. I can't climb ladders anymore so he wanted to install the cameras himself and to do so required splicing more wire into the feed from the wall plug mounted power supplies so I showed him how to test the DC power at the small power plug before plugging it into the camera. Anyway, I worked on his computer and DVR setting it up while he did the monkey work. ^_^

TDD

Reply to
The Daring Dufas

It took 4 1/2 hours but it came to me. It's called a Wheatstone bridge.

formatting link

A) It uses the values and ratios of 3 known resistors to measure an unknown resistance, and in a meter, since the ratios don't change with voltage, the value of an unknown (external) resistance, is not dependant on the votage of the battery.

However the url above only says "Variations on the Wheatstone bridge can be used to measure capacitance, inductance, impedance and other quantities," and "The concept was extended to alternating current measurements" and doesn't mention voltage or DC current.

In fact, a few lines up it says "If all four resistor values and the supply voltage (VS) are known, ....the voltage across the bridge (VG) can be found by working out the voltage from each potential divider and subtracting one from the other. " which implies that voltage measurements are dependant on knowing the battery voltage.

So maybe I was wrong, except wrt resistance and AC current (and very few meters measure AC current.)

^^Impedance is much like resistance, measured in ohms, but it's used for coils and caps, where it depends on frequency. If the frequency is 0, like it is with a battery, caps will have infinited impedance, but coils will have the impedance of a resistor made with the same length of the same wire.

Still, I've never read a warning that measurements are inaccurate as the battery weakens, and the guys who design these things are pretty clever, so I'm not giving up on the notion that, until the battery is almost dead, the voltage of the battery doesn't matter. Anyone know?

Reply to
micky

Autoranging is nice if you did not learn to use an old school meter where you'd start at the highest range and work down.

If you don't need autoranging Harbor Freight has an adequate one that is usually $5-6.

nate

Reply to
Nate Nagel

For what it's worth, I'm using NiMH rechargeable batteries in my Fluke meters (1.2V nominal/cell as opposed to 1.5V/cell for alkaline) I'm using a Tenergy Centura brand 7 cell/8.4V "9V" battery instead of the 6 cell 9V alkaline specified; I have noticed no inaccuracies in resistance readings.

I'm also using a Tenergy Centura D cell and similar "9V" battery in my Simpson 260 with no issues, but on the 260 you need to zero the meter every time you change resistance ranges anyway. However I suspect that it uses a similar circuit as the relative knob position ends up about the same for both alkalines and NiMH.

As an aside I've been happy after switching over to NiMH; hopefully I will not buy any more cells/batteries unless I buy more devices for a good long time.

nate

Reply to
Nate Nagel

Get a Sperry with a capacitor tester for about $60. May save you a couple hundred if your A/C quits.

Reply to
Bill

Hmmm, I perused eBay for Wavtek or Fluke for around 50.00. There were quite a few new and used ones for ~50.00. Thought that was pretty good deal for dependaable well built meters with decent accuracy RMS voltage reading ,etc. Good chance it'll last life time.

Reply to
Tony Hwang

Um, fatal voltage input. So, sort of. :-)

Reply to
Irreverent Maximus

Undoubtedly. Many people don't use a multimeter often enough or require enough accuracy/precision in readings to make it worth buying a Fluke however. I do agree that if willing to spend the money, Fluke, Agilent, etc. are excellent tools.

nate

Reply to
Nate Nagel

For complicated things and even high voltages, I still have analog, VTVM. ESR meter for caps. Right, vacuum tube. Good for measuring leakage resistance over 100 M.

My triplet goes a few KV.

Autorange is good if you can put it on manual.

I used to use the fluke snap on adaptors. Spike points, they really dug into the metal. handy most always for resistance.

Greg

Reply to
gregz

Digital is easy to read but unless I'm doing hi spec work, I prefer the old analog type. For one think, it's easier to see changes in reading with the needle swinging back and forth. If you every want to check the engine error codes, I can be difficult to do it with a digital meter.

$5-30 should get you something decent. I bought one at Radio Shack about 10 years ago for $25 that I could connect to a computer and record a time trace.

Reply to
Guv Bob

I usually end up measuring current when I'm messing around with cars - watching a battery charge, seeing how much current some accessory is drawing, stuff like that. That's why I spec'd the "high" current range. I haven't done it much on line-voltage AC; the times I have, I either used a clamp meter, or a Kill-a-Watt portable kWh meter. As others have noted, line-voltage AC stuff is more of a "it works or it doesn't" thing.

I firmly believe that as long as you have a tool with you, nothing that you can fix with that tool will ever break.

Matt Roberds

Reply to
mroberds

I was trouble shooting a car. Battery kept discharging. I attached ammeter into battery connection. After computer sleep, everything was good for a while. Then it would keep drawing current at intervals. After sitting in car I heard clicks. Click found to be coming from trunk. Bad radio antenna contacts trying to pull down antenna. Solution, pull relay with antenna extended.

Greg

Reply to
gregz

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.