Recommended testers for apprentice?

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Lxnxjxhx said:
Could be. . .it probably depends on the current drawn and the cold-cranking-amp rating.

I modeled this with a series circuit with 12v in series with an internal impedance in series with a starter motor drawing 400A with 4v across it. The motor then comes in at 10 milliohms, and the internal battery impedance has (12-4) volts across it at 400 A which gives 20 milliohms.

My unspoken assumption is that they used a car battery of some unspecified amp-hour rating to do the locked rotor test rather than coming up with some humongous thing that can source 1200A and still maintain 12v.
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A friend told me that they read very low, below 10 milliohms. I just measured one with a AC, 1000Hz type impedance meter at 6.4 milliohms. A DC load reading wouldn't probably read differently. As I remember DC load resistance was always a bit higher but not 3-4 times higher.
 
AC, 1000Hz

AC, 1000Hz

I've never heard of using AC for this purpose.
This tells me that to accurately model an electrochemical storage system like a lead-acid battery takes more than a series resistor.
Knowing this, I wouldn't be surprised if the impedance has some phase angle, and maybe the angle shifts depending on current draw, etc..

By the way, in one of National Semiconductor's Application Notes they said that small flashlight batteries may actually last longer when they are under a slight drain.
So much for the amp-hour capacity math model. . .
 
my two cents

my two cents

I use a Fluke 337 and a Fluke 87 what I do. Mostly motor control, drives and the like...

As a starter meter I have recommended the Fluke T-5's as a starter meter, I might also check into the Amprobe AM14T a wealth of meter for the price ($130.00 ish)

I also own a ideal ID 61 774, It has a life time warrantee, I'm on my 5th meter with a bad switch. { note the meter I use }
 
Lxnxjxhx said:
I've never heard of using AC for this purpose.
This tells me that to accurately model an electrochemical storage system like a lead-acid battery takes more than a series resistor.
Knowing this, I wouldn't be surprised if the impedance has some phase angle, and maybe the angle shifts depending on current draw, etc..

By the way, in one of National Semiconductor's Application Notes they said that small flashlight batteries may actually last longer when they are under a slight drain.
So much for the amp-hour capacity math model. . .
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If ome is refering to impedance, it's normally the 1000Hz AC test. It requires no loading of the battery. Many battery testers use this these days. Never heard of Midtronics? I used a Extech BT100 battery tester.

A resistance test normally means a DC load which runs down the battery and take time.
 
Another Vote for the Fluke T5-1000 or 600

Another Vote for the Fluke T5-1000 or 600

I think these are one of the best everyday carry around in your bag meters I have used. Easy to use and hard to break. Plus it won't empty your bank account either.
 
On reflection I think a new apprentice only needs a Fluke hot stick, votick or whatever it's called. Probably be good for the first year using his leads meter when necessary.
 
means a DC load which runs down the battery and take time

means a DC load which runs down the battery and take time

No, you just whack a heavy load on and you need to measure battery V loaded and unloaded, Rload and ILoad.
Then Rinternal = (12-RLoadILoad)/ILoad. Rinternal = Thevenin equivalent resistance. Same for measuring wall outlet impedance looking upstream.

Something doesn't seem right when you use an AC value for Rinternal when you are solving for values in a DC circuit. In the DC circuit I posted

". . .a series circuit with 12v in series with an internal impedance in series with a starter motor drawing 400A with 4v across it. The motor then comes in at 10 milliohms, and the internal battery impedance has (12-4) volts across it at 400 A which gives 20 milliohms."

I got 0.020 ohms.

Measuring amp-hour capacity at the 20 hour rate takes a while.
 
Lxnxjxhx said:
No, you just whack a heavy load on and you need to measure battery V loaded and unloaded, Rload and ILoad.
Then Rinternal = (12-RLoadILoad)/ILoad. Rinternal = Thevenin equivalent resistance. Same for measuring wall outlet impedance looking upstream.

Something doesn't seem right when you use an AC value for Rinternal when you are solving for values in a DC circuit. In the DC circuit I posted

". . .a series circuit with 12v in series with an internal impedance in series with a starter motor drawing 400A with 4v across it. The motor then comes in at 10 milliohms, and the internal battery impedance has (12-4) volts across it at 400 A which gives 20 milliohms."

I got 0.020 ohms.

Measuring amp-hour capacity at the 20 hour rate takes a while.
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You are measuring Z not just R. Z is a proven indacator of battery cell life expectantcy, like a load test, it is acceptable per IEEE 450 for load testing. Impednace testing with an AC signal has been done for battery systems for about 20 years, here is the test set we use.

http://www.megger.com/us/products/ProductDetails.php?ID=643&Description=

I suggest you read the IEEE 450 to learn about battery impedance.
 
measuring Z not just R

measuring Z not just R

How can I measure Z, and not just R, in a circuit that has no AC current flow, only DC current flow? This is the Thevenin equivalent resistance. . .?!

This is EE101, but I'd like to see what magic the IEEE has wrought. You have an online version of that IEEE spec?
 
Lxnxjxhx said:
How can I measure Z, and not just R, in a circuit that has no AC current flow, only DC current flow? This is the Thevenin equivalent resistance. . .?!

This is EE101, but I'd like to see what magic the IEEE has wrought. You have an online version of that IEEE spec?
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I dont think I can legally post an entire IEEE book that costs $$ to download, something about copyrights.

You, apply the AC signal to measure impedance. Look at the link I posted and read the tech notes if you want or Google "Battery Impedance Testing", this is common stuff to people that test battery systems.
 
There is a relatively new test that was developed and patented in the late 1980s by Commonwealth Edison and was commercialized in the early ?90s. It is called impedance, and it basically views the cells in a bank of batteries as resistors in a series connection. The higher the impedance of a cell, the less current it can generate (when a voltage is applied). Impedance
is just ac resistance. Impedance includes terms for inductance, capacitance, and frequency but at a constant frequency, this term becomes a constant. Changes in measured impedance are then due to actual differences in the internal impedance of a cell and not due to changes in frequency. By applying an ac current signal into a cell or across the entire bank, and measuring the ac voltage drop, impedance can be calculated using Ohm?s law, Z = V/i.
There is a strong correlation between battery capacity
and impedance, an internal ohmic test. As capacity decreases, impedance increases. Internal impedance can find weak cells in a battery bank with extremely high reliability. The Electric Power Research Institute conducted a study over about four years on approximately
30,000 cells comparing the value of internal ohmic testing, including impedance to battery capacity.
 
WOW! For a thread that started out on meters for apprentices, this one certainly sprouted wings. 95% of the journeymen I work with wouldn't understand some of the terminlogy in these posts, much less the best meter to use.
I have to agree with marc & a few others in recommending the Fluke T-5 series.
I have numerous meters on my truck and for well over 90% of what I encounter my ole trusty T5-1000 works well. It's duarble, easy to use and pretty much selfprotective. For my money, an ideal apprentice meter.

From some sad field investigations, my main input would to be avoid any meter that can self destruct if used improperly.
(Investigated more than one incident with an electrician using a cheap muti-meter checking voltage with the meter on resistance. The results can be disasterous)
 
Sorry, I was thinking we had strayed a little far as I was typing that post.

T5-1000, I agree, just make sure whatever they use is CATIII or IV rated.
 
I have to agree with the previous post about this thread 'sprouting wings'. I have to admit, what started out as (what i thought was) a fairly simple inquiry, has provided me with 'too much information', and some of the replys have gone way over this apprentice's head. I'm not trying to find a device to show off at the jobsite, but just want something durable, and accurate (for basic troubleshooting) that I can grow into as my knowledge/ability base expands. Thanks again for all the responses. The few weeks i've been lurking on this forum has provided more education than my less-than-adequate apprentice training (but that's a subject for another thread).
 
ichimo23 said:
..... The few weeks i've been lurking on this forum has provided more education than my less-than-adequate apprentice training (but that's a subject for another thread).
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don't let that deter you. the years I've spent here have provided more education than my less than adequate inspector/journeyman/contractor training. I'm sure I speak for others in welcoming new blood aboard
.. check in often.
 
ichimo23 said:
I have to agree with the previous post about this thread 'sprouting wings'. I have to admit, what started out as (what i thought was) a fairly simple inquiry, has provided me with 'too much information', and some of the replys have gone way over this apprentice's head. I'm not trying to find a device to show off at the jobsite, but just want something durable, and accurate (for basic troubleshooting) that I can grow into as my knowledge/ability base expands. Thanks again for all the responses. The few weeks i've been lurking on this forum has provided more education than my less-than-adequate apprentice training (but that's a subject for another thread).
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1st, welcome to the forum! It certainly is a great learning tool.

2nd, have you gotten a chance to see what the J-men you work with are using? It should give you a decent idea of what type of tester you would use the majority of the time. Ask if you can use them to see which you like. Ask around.
 
apprenticeship horror stories

apprenticeship horror stories

The 'journeymen' I work with are mostly recent ex-con alcoholics who dont own any decent testing equipment. Arizona is a right to work state, and any non-union electrician can call himself a journeyman if he has 4 years of experience (nobody verifies this). If the owner of the company has a contractor's license, any monkey can work under him and do everything from pull wire to make up panels etc with no experience (not legally of course). I know that for a fact, since that's what i did. My first day on the job (no previous electrical experience), i was dropped off at a vacant commercial building with a 12' ladder and a 10 in 1 screwdriver, and told to demo a bunch of conduit and j-jboxes. The guy dropped me off and said he'd be back in a few hours. I climbed up the ladder to disconnect the first jbox and got bolted real nice, and experienced my first hard ground fault (so i got a nice shock and then the flash/sparks). At least the guy was apologetic and offered an 'oops' when i told him what happened. I've worked panels live taking direction over a cell phone, not knowing what i as doing. I didnt know any better, but as i get more educated (enrolled in local trade school which i'm paying for out of my own pocket) i've come to realize how dangerous some of the things i'm asked to do is. I'll currently looking for a 'real' contractor to work with now that i have a bit of 'experience'...
 
ichimo23 said:
... i was dropped off at a vacant commercial building with a 12' ladder and a 10 in 1 screwdriver, and told to demo a bunch of conduit and j-jboxes. The guy dropped me off and said he'd be back in a few hours. I climbed up the ladder to disconnect the first jbox and got bolted real nice, and experienced my first hard ground fault (so i got a nice shock and then the flash/sparks).

... I've worked panels live taking direction over a cell phone, not knowing what i as doing. ...
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That's grounds for punching your boss right square in the jaw. You missed your chance to fall on the ground, lay there, call 911 from your cell, and own his butt.
 
ichimo23 said:
The 'journeymen' I work with are mostly recent ex-con alcoholics who dont own any decent testing equipment. Arizona is a right to work state, and any non-union electrician can call himself a journeyman if he has 4 years of experience (nobody verifies this). If the owner of the company has a contractor's license, any monkey can work under him and do everything from pull wire to make up panels etc with no experience (not legally of course). I know that for a fact, since that's what i did. My first day on the job (no previous electrical experience), i was dropped off at a vacant commercial building with a 12' ladder and a 10 in 1 screwdriver, and told to demo a bunch of conduit and j-jboxes. The guy dropped me off and said he'd be back in a few hours. I climbed up the ladder to disconnect the first jbox and got bolted real nice, and experienced my first hard ground fault (so i got a nice shock and then the flash/sparks). At least the guy was apologetic and offered an 'oops' when i told him what happened. I've worked panels live taking direction over a cell phone, not knowing what i as doing. I didnt know any better, but as i get more educated (enrolled in local trade school which i'm paying for out of my own pocket) i've come to realize how dangerous some of the things i'm asked to do is. I'll currently looking for a 'real' contractor to work with now that i have a bit of 'experience'...
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Sorry about that, I know some good companies in Pheonix, you interested in learning about power systems and testing?
 
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