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19-06-2013, 20:18
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#76
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Nearly an old salt

Join Date: Jun 2009
Posts: 13,648
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Re: Multimeters - What Features To Look For.
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19-06-2013, 20:55
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#77
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֍֎֍֎֍֎֍֎֍֎

Join Date: Apr 2006
Posts: 14,907
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Re: Multimeters - What Features To Look For.
Foggy-
"Hall" isn't a brand. The "Hall Effect" is the physical interplay between a magnetic field and a Hall Effect Semiconductor, much the same as the way light causes a reaction in a solar panel. It allows for much more sensitive reading of magnetic fields than a simple magnetic induction coil would.
And yes, shunts are expensive. The $4 shunt from China looks like a piece of scrap iron next to a typical $25 US shunt. I wouldn't bet on how well it ages in salt air or how well it has been calibrated, thermally compensated, etc. Bought a cheap Shenzhen digital meter to see what I'd get, and the plastic in front of the LEDs warped from room heat within a week. They were also unreadable in sunlight. (Large green display.)
If the $4 job works good enough for you...great. I can buy a foot of power cable for less and use it the same way.
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05-09-2013, 17:00
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#78
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Registered User
Join Date: Jul 2013
Location: San Diego, CA
Posts: 3,530
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Re: Multimeters - What Features To Look For.
I'm going to offer MHO, and while some of you may disagree with it, it's based on 30 yrs of hands-on electronics background (10 yrs Navy sub ET, 11 yrs defense contractor and 9 yrs self employed.)
As a defense contractor, all of our test equipment was required to be calibrated at the Navy's cal lab. Most of my coworkers used Fluke 77s, one guy bought a Fluke 87 and I bought a Centech which had all of the same features as the 87, but IIRC, it was only $35 instead of $350. We sent them in to cal and mine came back calibrated, his $350 Fluke 87 could not be calibrated - brand new, right out of the box. Of course he returned it, and got another one which passed cal. I still use the $35 one occasionally, but I usually use the $3.99 Cen Techs from HF. Why? Because they're so cheap, if one gets broken, no big deal. Plus for the last 9 yrs, I've had no requirement to have a calibrated DMM, so the cheap ones do what I need them to. Most of the time, someone asks me to help them diagnose a problem with their RV, and they don't own a meter or know how to use one. I bring over a $4 meter, I show them how to use it, diagnose the problem, help them fix it (if we don't need parts from town), drink a couple of beers and give them the DMM. I keep them around like chewing gum. One in each vehicle, 3 or 4 in the trailer to give away, a couple in the house.
I just compared one of my $4 DMM to the calibrated meter using a NiZn battery. The calibrated meter registered 1.563 VDC. The $4 meter registered 1.565 VDC. So the cheapo meter was off by .002 V on the 2 volt scale. I don't think 2 millivolts is going to mislead any DIY guy tracking down 120v or 12v.
Why do I mention this? Because many of us (and I still do this a lot) equate more expensive with higher quality. But often, there isn't a direct correlation between price and quality. The only way to tell the quality of a DMM is to either do some research on electronics hobbyist websites (let someone else buy one and open it up) or take a chance and buy one that you think might be good. My search today indicates it looks like my meter was pretty popular in it's day, but is no longer in production. The current model number is Mastech M9508, which is also hard to find.
I'm not saying that every $4 DMM is as good or as accurate as a Fluke, but I am stating this: after using and passing out probably 15 - 20 of the cheapo DMMs, I never saw one that appeared to be off by more than .01v on the DCV scale. At the same time, spending almost $400 for a Fluke 87-V will buy you an uncalibrated meter. You'll have to order and pay extra for calibration.
I don't currently own a boat, but I am fairly familiar with Murphy's law which I believe is very closely related. One of the more obscure corollaries of Murphy's Law is:
The probability of a piece of test equipment (or repair parts) falling into the bilge or getting knocked over the side into the water rises exponentially with the cost of the test equipment or part. In accordance with that, even though the $4 units are cheap, they'll probably never go away - like the proverbial ex-wife who claims you still owe her child support.
What I'd suggest is buy a couple of the cheapo DMMs for every day use. If it breaks or gets wet, no big loss. Then as others have suggested, pick up a good quality True RMS DMM for $150 or less (Agilent, BK Precision, Mastech, and others look pretty good) and a good quality clamp on ammeter (like the Mastech MS2108 I just got on Ebay for $61) and tie a string around both so they don't go in the water. This way if you ever need the added accuracy and/or precision, you have it.
Sometimes (actually all of the time), the talent of the technician or handyman is far more important in troubleshooting success than the price of his test equipment.
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05-09-2013, 18:40
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#79
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Senior Cruiser

Join Date: Jul 2007
Location: W Florida
Boat: The Jon boat still, plus a 2007 SeaCat.
Posts: 6,958
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Re: Multimeters - What Features To Look For.
Quote:
Originally Posted by socaldmax
I'm going to offer MHO, and while some of you may disagree with it, it's based on 30 yrs of hands-on electronics background (10 yrs Navy sub ET, 11 yrs defense contractor and 9 yrs self employed.)
As a defense contractor, all of our test equipment was required to be calibrated at the Navy's cal lab. Most of my coworkers used Fluke 77s, one guy bought a Fluke 87 and I bought a Centech which had all of the same features as the 87, but IIRC, it was only $35 instead of $350. We sent them in to cal and mine came back calibrated, his $350 Fluke 87 could not be calibrated - brand new, right out of the box. Of course he returned it, and got another one which passed cal. I still use the $35 one occasionally, but I usually use the $3.99 Cen Techs from HF. Why? Because they're so cheap, if one gets broken, no big deal. Plus for the last 9 yrs, I've had no requirement to have a calibrated DMM, so the cheap ones do what I need them to. Most of the time, someone asks me to help them diagnose a problem with their RV, and they don't own a meter or know how to use one. I bring over a $4 meter, I show them how to use it, diagnose the problem, help them fix it (if we don't need parts from town), drink a couple of beers and give them the DMM. I keep them around like chewing gum. One in each vehicle, 3 or 4 in the trailer to give away, a couple in the house.
I just compared one of my $4 DMM to the calibrated meter using a NiZn battery. The calibrated meter registered 1.563 VDC. The $4 meter registered 1.565 VDC. So the cheapo meter was off by .002 V on the 2 volt scale. I don't think 2 millivolts is going to mislead any DIY guy tracking down 120v or 12v.
Why do I mention this? Because many of us (and I still do this a lot) equate more expensive with higher quality. But often, there isn't a direct correlation between price and quality. The only way to tell the quality of a DMM is to either do some research on electronics hobbyist websites (let someone else buy one and open it up) or take a chance and buy one that you think might be good. My search today indicates it looks like my meter was pretty popular in it's day, but is no longer in production. The current model number is Mastech M9508, which is also hard to find.
I'm not saying that every $4 DMM is as good or as accurate as a Fluke, but I am stating this: after using and passing out probably 15 - 20 of the cheapo DMMs, I never saw one that appeared to be off by more than .01v on the DCV scale. At the same time, spending almost $400 for a Fluke 87-V will buy you an uncalibrated meter. You'll have to order and pay extra for calibration.
I don't currently own a boat, but I am fairly familiar with Murphy's law which I believe is very closely related. One of the more obscure corollaries of Murphy's Law is:
The probability of a piece of test equipment (or repair parts) falling into the bilge or getting knocked over the side into the water rises exponentially with the cost of the test equipment or part. In accordance with that, even though the $4 units are cheap, they'll probably never go away - like the proverbial ex-wife who claims you still owe her child support.
What I'd suggest is buy a couple of the cheapo DMMs for every day use. If it breaks or gets wet, no big loss. Then as others have suggested, pick up a good quality True RMS DMM for $150 or less (Agilent, BK Precision, Mastech, and others look pretty good) and a good quality clamp on ammeter (like the Mastech MS2108 I just got on Ebay for $61) and tie a string around both so they don't go in the water. This way if you ever need the added accuracy and/or precision, you have it.
Sometimes (actually all of the time), the talent of the technician or handyman is far more important in troubleshooting success than the price of his test equipment.
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Thanks for your input.
I put the Mastech on my wish list.
Where are the $4.00 meters?
I want a couple for the boys.
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05-09-2013, 19:26
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#80
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֍֎֍֎֍֎֍֎֍֎

Join Date: Apr 2006
Posts: 14,907
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Re: Multimeters - What Features To Look For.
If you watch the Horror Fright magazine ads, sometimes they are literally giving away the $5 or $10 multimeters. I picked one up that way figuring I can keep it in the car and if it gets stolen, I'm not out a lot of money.
Also got around to testing it versus a calibration source, which put out 10.00 VDC precisely. And compared to my other meters...the HF meter was about as close as a test light. I've never seen one so far off, including one that was ten years old and had a good chance to age and drift before it ever got tested.
Maybe I just got the winner, like the bad Fluke. But as a test light, it works just fine. It will never earn my trust as the "go to" meter though.
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05-09-2013, 19:33
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#81
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Registered User
Join Date: Jul 2013
Location: San Diego, CA
Posts: 3,530
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Re: Multimeters - What Features To Look For.
Quite often Harbor Freight has their Cen Tech 7 function DMM for sale for $3.99. When I need some, I just stock up on a few more. A lot of stuff that HF sells is junk (especially their LED flashlights), some of it is OK - consumable items like grinding disks are OK. I've found that by really looking closely at whatever the tool or item is, I can pretty much tell the decent quality items from the junk. If you don't like it, they'll always take it back.
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05-09-2013, 19:46
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#82
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Registered User
Join Date: Jul 2013
Location: San Diego, CA
Posts: 3,530
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Re: Multimeters - What Features To Look For.
Quote:
Originally Posted by hellosailor
If you watch the Horror Fright magazine ads, sometimes they are literally giving away the $5 or $10 multimeters. I picked one up that way figuring I can keep it in the car and if it gets stolen, I'm not out a lot of money.
Also got around to testing it versus a calibration source, which put out 10.00 VDC precisely. And compared to my other meters...the HF meter was about as close as a test light. I've never seen one so far off, including one that was ten years old and had a good chance to age and drift before it ever got tested.
Maybe I just got the winner, like the bad Fluke. But as a test light, it works just fine. It will never earn my trust as the "go to" meter though.
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Here's a good example of someone having the opposite experience I did. Not that I think any of the HF DMMs are calibrated, but they're only $4, not $400.
I look at them as consumables, and they're good enough to tell me if an alternator is charging, or if there is a bad connection.
They're so cheap, it's almost not even worth the gas to drive back to HF to exchange for another one, unless you have several or other items to take back. For important measurements, one should have a true RMS DMM, I just think you can find plenty of good ones in the sub $100 or $150 range.
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06-09-2013, 10:56
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#83
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Senior Cruiser

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 20,888
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Re: Multimeters - What Features To Look For.
I work on vintage vacuum tube amplifiers alot. Over the years I have tried a couple of cheap VOM's. Radio Shack & another hardware store one. Both were severely off in some ranges of V and Milliamps. I have a small Fluke that I bought in '88. It is still going strong. Frankly I dont think you need an expensive meter for a boat.... most of what you are measuring is DCV. But how to know if it's any good to start with?
I put a $5 Digital voltmeter on my boat recently with a STDP switch to be able to check each batterys voltage. Works great and is right on with t he Fluke reading. Go figure....
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"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
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08-09-2013, 19:20
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#86
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Senior Cruiser

Join Date: Jul 2007
Location: W Florida
Boat: The Jon boat still, plus a 2007 SeaCat.
Posts: 6,958
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Re: Multimeters - What Features To Look For.
Quote:
Originally Posted by hellosailor
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But what does the "A" mean?
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08-09-2013, 19:31
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#88
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Senior Cruiser

Join Date: Jul 2007
Location: W Florida
Boat: The Jon boat still, plus a 2007 SeaCat.
Posts: 6,958
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Re: Multimeters - What Features To Look For.
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08-09-2013, 20:11
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#90
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Registered User
Join Date: Jul 2013
Location: San Diego, CA
Posts: 3,530
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Re: Multimeters - What Features To Look For.
Yup, the vendor selling the "MS2108" for $39.95 left the "A" off the end. Maybe accidental, but I'm guessing it wasn't.
I did buy an MS2108 on Ebay for $61. It will take another week for it to arrive.
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