Author Topic: Advice on a new DMM  (Read 18052 times)

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alm

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Re: Advice on a new DMM
« Reply #25 on: September 23, 2011, 10:15:53 pm »
Note that searching for meters with hFE measurements will give you the lower quality meters with many features. The hFE sockets are rarely isolated very well, if you're measuring dangerous voltage, this voltage is also likely on the transistor socket. Few, if any, high-quality meters are able to measure hFE. Since the DC current gain is a function of collector current and temperature, it's not a very useful measurements. About the only thing it's good in my opinion for is figuring out the polarity, pin-out and if it's shorted. Two or three diode measurements will tell you the same, however, and will work with a much wider range of devices and packages (eg. TO-220, or SOT-23).
 

Offline SgtRock

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Re: Advice on a new DMM
« Reply #26 on: September 23, 2011, 10:45:30 pm »
Dear Alm:

--Thanks for the spot on comments. I have always wondered why hFE was only on the cheaper meters.

“I do believe that it's the first time in history that fire has ever melted steel." Rosie O'Donnell

Best Regards
Clear Ether
 

Online IanB

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Re: Advice on a new DMM
« Reply #27 on: September 23, 2011, 10:47:51 pm »
Note that searching for meters with hFE measurements will give you the lower quality meters with many features. The hFE sockets are rarely isolated very well, if you're measuring dangerous voltage, this voltage is also likely on the transistor socket. Few, if any, high-quality meters are able to measure hFE. Since the DC current gain is a function of collector current and temperature, it's not a very useful measurements. About the only thing it's good in my opinion for is figuring out the polarity, pin-out and if it's shorted. Two or three diode measurements will tell you the same, however, and will work with a much wider range of devices and packages (eg. TO-220, or SOT-23).
With the RS 22-812 meter I mentioned above the transistor test socket is closed off with a locking shutter when the meter probes are inserted, so it is impossible for this socket to be exposed when measuring voltages. Likewise the meter probes cannot be inserted when the transistor test function is being used. It's pleasing they considered that in the design.

On the utility of  hFE sockets in general, I imagine they can help to get a ball park estimate, and also could help if trying to match two transistors with similar gains?
 

Offline Lightages

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Re: Advice on a new DMM
« Reply #28 on: September 23, 2011, 11:54:49 pm »

On the utility of  hFE sockets in general, I imagine they can help to get a ball park estimate, and also could help if trying to match two transistors with similar gains?

I too think that hFE measurement features are rather pointless and usually indicate a poorer quality meters. They can be useful however for matching and sorting transistors of certain types but I would have a separate meter to do that and not as my main and safe meter. A meter with hFE can be purchase for only a few dollars.

But, as the original poster specified hFE as a plus for his meter, it is his choice.
 

Online IanB

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Re: Advice on a new DMM
« Reply #29 on: September 24, 2011, 12:26:42 am »
I too think that hFE measurement features are rather pointless and usually indicate a poorer quality meters. They can be useful however for matching and sorting transistors of certain types but I would have a separate meter to do that and not as my main and safe meter.
I'm not sure about the reference to "main and safe meter". Surely one should buy the right tools for the job? I have two of the 22-812 meters (among other meters) that live on my home workbench as electronics lab tools to measure low energy circuits and I'm thinking about getting a third. The 22-812 is CAT II rated, and considering the highest energy circuit I am ever likely to measure is the domestic mains, that is quite sufficient. A CAT III or CAT IV meter would be entirely pointless and would involve paying for features I don't need. Better for my purposes that I have two multi-featured meters with data logging facilities than one more expensive meter without.

The transistor test socket is a bonus that comes with the meter along with the other features like capacitance, frequency, duty cycle, pulse width, logic level, max/min, rel, hold, uA, diode test--all of which indicate suitability as a lab meter.

Various people seem to be turning their nose up at this meter because it comes from "Radio Shack", but more fool them, they are missing a bargain.
 

Offline Kiriakos-GR

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Re: Advice on a new DMM
« Reply #30 on: September 24, 2011, 01:19:03 am »
Various people seem to be turning their nose up at this meter because it comes from "Radio Shack", but more fool them, they are missing a bargain.

Well you had wrote few lines of software about it, and probably you have emotional ties with it,
but every one makes his own decisions, and your advertising method does not help any.   
 

Online IanB

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Re: Advice on a new DMM
« Reply #31 on: September 24, 2011, 02:03:40 am »
Well you had wrote few lines of software about it, and probably you have emotional ties with it,
but every one makes his own decisions, and your advertising method does not help any.
Don't be silly. All I did was make one post suggesting it was worth a look, and someone came along and made bullshit claims out of their ass saying it had no isolation and would blow up your computer, without any knowledge or evidence to back it up. That's a good way to derail a thread but it's not very enlightening.
 

Uncle Vernon

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Re: Advice on a new DMM
« Reply #32 on: September 24, 2011, 02:56:46 am »
Well you had wrote few lines of software about it, and probably you have emotional ties with it,
but every one makes his own decisions, and your advertising method does not help any.
Don't be silly. All I did was make one post suggesting it was worth a look, and someone came along and made bullshit claims out of their ass saying it had no isolation and would blow up your computer, without any knowledge or evidence to back it up. That's a good way to derail a thread but it's not very enlightening.
advertising?  emotional ties.

Must be on drugs!  Ignore the static, your comment about selecting a device appropriate for intended use has been the most sensible advice offered in this thread. 
 

Offline Lightages

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Re: Advice on a new DMM
« Reply #33 on: September 24, 2011, 06:55:25 am »
I too think that hFE measurement features are rather pointless and usually indicate a poorer quality meters. They can be useful however for matching and sorting transistors of certain types but I would have a separate meter to do that and not as my main and safe meter.
I'm not sure about the reference to "main and safe meter". Surely one should buy the right tools for the job? I have two of the 22-812 meters (among other meters) that live on my home workbench as electronics lab tools to measure low energy circuits and I'm thinking about getting a third. The 22-812 is CAT II rated, and considering the highest energy circuit I am ever likely to measure is the domestic mains, that is quite sufficient. A CAT III or CAT IV meter would be entirely pointless and would involve paying for features I don't need. Better for my purposes that I have two multi-featured meters with data logging facilities than one more expensive meter without.

The transistor test socket is a bonus that comes with the meter along with the other features like capacitance, frequency, duty cycle, pulse width, logic level, max/min, rel, hold, uA, diode test--all of which indicate suitability as a lab meter.

Various people seem to be turning their nose up at this meter because it comes from "Radio Shack", but more fool them, they are missing a bargain.

My statement was "usually indicate" and that my personal opinion was that hFE was not that useful. If it is to you and you have a meter with this feature and it meets your needs, then all is good. I am not a brand snob. I have a Radio Shack pen style multimeter that performs well and is rather accurate.

As far as insults from other people about your posts, ignore them.
 

Offline EEVblog

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Re: Advice on a new DMM
« Reply #34 on: September 24, 2011, 12:08:29 pm »
Note that searching for meters with hFE measurements will give you the lower quality meters with many features. The hFE sockets are rarely isolated very well, if you're measuring dangerous voltage, this voltage is also likely on the transistor socket. Few, if any, high-quality meters are able to measure hFE.

Correct.
In fact I'd go as far to say that no high quality reputable meter has a hFE function.
I think I mentioned in my multimeter tutorial video that a hFE feature feature is a basic way to differentiate a good quality meter from a OneHungLow cheapie.

But granted, hFE may be useful to some people in some circumstances, but if so, you can just use $5 cheapie for that.
And a meter having hFE does not of course automatically mean it is crap of course, you have to weight up each meter on it merits. But it obvious which way to bet  ;D

Dave.
 

Offline EEVblog

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Re: Advice on a new DMM
« Reply #35 on: September 24, 2011, 12:40:20 pm »
I have no experience with Protek, but this one:
http://www.tequipment.net/Protek608.asp
is only $9 more than your budget and meets everything you want as far as I can see. It also seems to get some positive comments where I have been able to find any reviews. As far as its build quality and safety I cannot comment. If it actually meets its specifications and has decent build quality, it is a bargain.

The Protek 506 was a classic RS-232 interface meter, and had a very long product life and was very popular.
I can't recall the internal quality, but it was a pretty decent meter for the money.
Off hand, the Protek 608 does look hard to beat at that price point, and I'd probably agree that it looks like a bargain.
How many other 0.05% 50,000 count class meters for $120 are there?
The Uni-T UT71 series is one.
Did someone do a teardown on the UT71 on the forum?
I haven't touched either, but my money would be on the Protek being the better quality unit.

Dave.
 

Offline Lightages

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Re: Advice on a new DMM
« Reply #36 on: September 24, 2011, 03:40:53 pm »
I have a UT71E, and for the price at the time and the semi-good reputation of UniTrend I thought I would give one a try. It did not meet any of its specs out of the box.

I will be doing a teardown sometime and a mini-review. I would not recommend a UT71 series at this point. I have taken the UT71E apart and it has OK construction inside but very little input protection. I did not take any pictures yet.

I might just order one of those Protecs to see for myself too.
« Last Edit: September 24, 2011, 07:00:26 pm by Lightages »
 

Offline jaimeroldanTopic starter

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Re: Advice on a new DMM
« Reply #37 on: September 24, 2011, 06:50:55 pm »
Yep, i was no expecting to pay more than 70 for a Uni-T. They are an okay option. In the other hand, the protek looks promising. I'm going to research a little more.
BTW i have a fluke 110 right now, but the lack of amps is just ... lame.
 


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