Author Topic: Uni-T 216D Clamp meter for house and raspberry pi? Also how safe are probes?  (Read 2126 times)

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Offline dreno

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Hi,
I was looking forward to buy a multimeter for all the stuff around the house. Car, photovoltaics and so on. Also I am doing some stuff with raspberry pi, like running a home automation server with humidity and temperature sensors.

I was reading that the Uni-T 216D would be nice for photovoltaics and heatpumps as it is rated till 1000V. I wanted to buy it but I am not so sure what I am able to do with the probes? Are the probes safe to use? Do they need to be fused, or will this only protect the device? Also it is not possible to measure mA with them? Do you know when there is a need to measure mA with the probes, actually I am not sure if I need the mA feature. Or maybe you can suggest me some other device???

Sorry, but I am new to the subject.

dreno
 

Online Fungus

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The only thing you can measure with the clamp is current (amps), everything else uses the probes.

For "Raspberry Pi" you almost certainly need milliamps.

As an only meter, I don't think this meter is a good choice. At least pair it with one of those cheap Chinese meters for the non-mains work.

(I like my ANENG 860B+ for small electronics work, they're about $20)
 
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Offline dreno

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I was reading a bit more, so I need fuses only when I have a device where I can measure amps with the probes? Which is not the case with the clamp meter, so there is no fuse needed?

why are the chinese meters not good for mains work?

wow, the Aneng meters are so cheap. Which is the "best" they offer, there is something better than the 860B+?

I am not sure what I need measure mAmps, can you tell me maybe an example?
 

Online Fungus

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I was reading a bit more, so I need fuses only when I have a device where I can measure amps with the probes? Which is not the case with the clamp meter, so there is no fuse needed?

Correct. The fuses in multimeters are only on the amps ranges.

The other ranges have a very high resistance (eg. 10 MOhm) so not enough current can flow to make a fuse useful.

why are the chinese meters not good for mains work?

The answer to that question is very long and hardly anybody is qualified to answer it fully because the standards are only available to people who pay for them.

Most of the fuss about those meters is because they print false CAT ratings on the front. The CAT ratings printed on them might be true on the voltage ranges but CAT ratings are supposed to apply to all ranges, not just the voltage.

eg. Many of them say CAT III 100V on the front but when you open them up the fuses will say "250V".

Short version: If you're at home and you double-triple-check you're on a current range before probing then you're probably OK.

nb. you shouldn't be using probes to measuring current on mains devices - use a clamp for that.

wow, the Aneng meters are so cheap. Which is the "best" they offer, there is something better than the 860B+?

The 860B+ is near the top and plenty good enough for most things. You can get more digits if you want but it's not very useful/essential. Remember that most electronic components and power supplies are only 5 or 10 percent accurate.

The ANENG 870 is the next step up.

I am not sure what I need measure mAmps, can you tell me maybe an example?

LEDs are measured in mA.

If you want to know the consumption of a gadget powered by AA/AAA/9V batteries, that will be in mA (or maybe even uA!).


You mentioned "auto" work. Cars are where current clamps really shine. You just clamp it around a wire and read it. Even connecting a meter to a car using probes is a pain in the ass.

Bottom line: Only you know what you want the meter for and one meter is never enough.  Sometimes you need two meters at once (eg. for calculating power) :popcorn:
« Last Edit: January 12, 2019, 12:14:20 pm by Fungus »
 
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Offline dreno

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Thank you very much! Excellent advice!

So you seem to know the ANENG meters. The ANENG 870 would cost me 6 bucks more. What comes next after the ANENG 870? Is there a difference between the ANENG 860B+ and the ANENG 870, or only more numbers? Maybe it has some nice improved feature?

So I will buy the clamp. I think there is not much difference between the 216C and the 216D? Is an OLED display something valuable or maybe is it crap (I think at least the light with this meter will stay always on ;-))?

So I guess you are in the Test Equipment Anonymous (TEA) group therapy? hahaha :-D
 

Online Fungus

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Is an OLED display something valuable or maybe is it crap (I think at least the light with this meter will stay always on ;-))?

Only if you enjoy replacing batteries and want it to fade to unreadable in about three years.
 
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Offline dreno

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Is an OLED display something valuable or maybe is it crap (I think at least the light with this meter will stay always on ;-))?

Only if you enjoy replacing batteries and want it to fade to unreadable in about three years.

Seriously???
 

Offline janoc

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Most of the fuss about those meters is because they print false CAT ratings on the front. The CAT ratings printed on them might be true on the voltage ranges but CAT ratings are supposed to apply to all ranges, not just the voltage.

eg. Many of them say CAT III 100V on the front but when you open them up the fuses will say "250V".

Short version: If you're at home and you double-triple-check you're on a current range before probing then you're probably OK.


Um, nope. That's actually a pretty dangerous advice. It would be ok if the only problem were the fake CAT ratings. The problem is that many of these meters are also dangerously unsafe for use around mains - minimal/no input protections, nonexistent creepage/clearance, wrong fuses - e.g. glass instead of proper HRC ones, etc.

That's all fine and dandy while there is no fault or power transient on the mains. Once there is, the meter could easily suddenly go KABOOM in your hands.

I would suggest the OP to get a basic but good electrician's meter for the mains/photovoltaics stuff where high voltages or transients are likely and buy a cheap Chinese one for the Raspberry Pi or car where a lack of input protection isn't risking your life.
 
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Offline janoc

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Is an OLED display something valuable or maybe is it crap (I think at least the light with this meter will stay always on ;-))?

Only if you enjoy replacing batteries and want it to fade to unreadable in about three years.

Seriously???

Yeah, OLED displays fade over time and they are notorious battery hogs - they are basically LEDs, eating a lot of current to show the value, unlike an LCD which takes very little (not counting backlight).
 
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Offline dreno

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Most of the fuss about those meters is because they print false CAT ratings on the front. The CAT ratings printed on them might be true on the voltage ranges but CAT ratings are supposed to apply to all ranges, not just the voltage.

eg. Many of them say CAT III 100V on the front but when you open them up the fuses will say "250V".

Short version: If you're at home and you double-triple-check you're on a current range before probing then you're probably OK.


Um, nope. That's actually a pretty dangerous advice. It would be ok if the only problem were the fake CAT ratings. The problem is that many of these meters are also dangerously unsafe for use around mains - minimal/no input protections, nonexistent creepage/clearance, wrong fuses - e.g. glass instead of proper HRC ones, etc.

That's all fine and dandy while there is no fault or power transient on the mains. Once there is, the meter could easily suddenly go KABOOM in your hands.

I would suggest the OP to get a basic but good electrician's meter for the mains/photovoltaics stuff where high voltages or transients are likely and buy a cheap Chinese one for the Raspberry Pi or car where a lack of input protection isn't risking your life.

You think even the clamp is unsafe?

Would measuring voltage with the probes of the clamp meter be unsafe somehow?
 

Online Fungus

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Short version: If you're at home and you double-triple-check you're on a current range before probing then you're probably OK.

Did I type "current"?  :palm:

I did of course mean "voltage".

Um, nope. That's actually a pretty dangerous advice. It would be ok if the only problem were the fake CAT ratings. The problem is that many of these meters are also dangerously unsafe for use around mains - minimal/no input protections, nonexistent creepage/clearance, wrong fuses - e.g. glass instead of proper HRC ones, etc.

a) If you're on voltage range then the fuses don't enter into it.
b) The $20 Chinese meters all have some sort of input protection, at least a MOV.

For occasional use the danger is minimal. I'm not saying it's not there but "very dangerous" is an exaggeration.

OTOH I'd never recommend one for an electrician who does this every day. For that I'd get a proper safe meter.

And with that, this thread has now devolved into the 1,002nd "how do you define a safe meter" thread on EEVBLOG.
 
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Online Fungus

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You think even the clamp is unsafe?

It's difficult to do damage using just the 'clamp' part of a clamp meter. Maybe there's a loose wire that you pull out.

Would measuring voltage with the probes of the clamp meter be unsafe somehow?

About as safe as using an ANENG multimeter with the fuses removed.

Notes:
a) Using a Fluke carelessly and without knowing what you're doing can be dangerous, too.
b) The photos on the Fluke web site always show Fluke users wearing gloves, face masks and hearing protection when measuring mains AC, presumably to avoid legal liability.
« Last Edit: January 12, 2019, 07:18:07 pm by Fungus »
 
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Online Fungus

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Short version:

The best advice anybody can give for how to measure mains AC is "don't!"

After that, the advice would be to, "Plug in a lamp. If it lights up at normal brightness then the mains is working just fine".


 
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Offline dreno

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Actually I saw the meters are really cheap on aliexpress or banggood. Some even have warehouses in my country. I never bought before there. So what I buy there it is the "original" Uni-t/Aneng or do the chinese even copy the chinese brands and I have to watch out for fakes????
 

Online Fungus

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So what I buy there it is the "original" Uni-t/Aneng or do the chinese even copy the chinese brands and I have to watch out for fakes????

Nah, no fakes at these prices.

You can always buy from the official store if you want to be sure: https://www.aliexpress.com/store/919484
 
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Offline joeqsmith

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Correct. The fuses in multimeters are only on the amps ranges.

That has not been my experience.  Some of the cheap meters have shared the current input jack with other features.  In these cases, I have seen a few (not very many) where the fuse for the current also feeds all the other circuits.   The last Analog meter one I saw like this was sold under the tech power brand.  The last Digital one was sold under the Radio Shack brand. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 
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Online Fungus

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Correct. The fuses in multimeters are only on the amps ranges.

That has not been my experience.  Some of the cheap meters have shared the current input jack with other features.  In these cases, I have seen a few (not very many) where the fuse for the current also feeds all the other circuits.   The last Analog meter one I saw like this was sold under the tech power brand.  The last Digital one was sold under the Radio Shack brand.

Joe, the man who can find an exception to every rule...

In Dave's "input protection" video he only drew fuses on the current ranges:



That's because you have to try really hard to find one that doesn't work that way.


« Last Edit: January 12, 2019, 08:15:14 pm by Fungus »
 
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Online HKJ

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The best advice anybody can give for how to measure mains AC is "don't!"

Oh, please. Ordinary mains it not that dangerous (UK may be an exception with 240V & 30A fuses), the power is fairly limited and just about any meter can handle voltages below 250VAC with a 16A fuse (or lower). The meter may "explode" if you are unlucky, but that "explosion" will be fairly limited.

But measuring on higher voltage (with current) or higher current circuits I would not use a cheap meter.
 
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Offline joeqsmith

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I provided a couple of examples and stated it was uncommon.   

Dave does more mechanical tests like  twisting, swimming, dropping, knocking them off their stand  than testing the electronics.  He may have had meters that have the fuse inline with functions besides current and not been aware of it.   

I focus more on the electronics side of testing and when you test as many low end meters to failure as I have, you tend to see a few things. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online Fungus

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The best advice anybody can give for how to measure mains AC is "don't!"
Oh, please. Ordinary mains it not that dangerous (UK may be an exception with 240V & 30A fuses), the power is fairly limited and just about any meter can handle voltages below 250VAC with a 16A fuse (or lower).

Why do you need to measure it? Is it likely to show the wrong value? Why is a number to two decimal places better than a light bulb?
 
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Offline dreno

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Thanks for the cool video!!!

So there might be voltage spikes in mains? Or in the line to the switchboard???

What can happen to a multimeter if there are voltage spikes? It will just break or will it explode?
 

Online Fungus

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What can happen to a multimeter if there are voltage spikes? It will just break or will it explode?

Which multimeter? How many volts? How long is a piece of string?
 

Online Fungus

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If you insist on poking at AC mains then the only way to make everybody people here happy is to buy three meters:
a) A Fluke 101 for the mains (no current ranges)
b) A clamp for your car (probably Uni-T)
c) ANENG meter for raspberry Pi (mA, etc).

You can probably get all three for not much more than $100, delivered.

Can you do it all with a single $120 meter? No, because you won't have a clamp and you sometimes need two meters simultaneously.
 
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Online HKJ

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So there might be voltage spikes in mains? Or in the line to the switchboard???

What can happen to a multimeter if there are voltage spikes? It will just break or will it explode?

Mains have voltage spikes, especially if you live in industrial areas.
A spike may damage a meter (See Joe's videos) or it may even start an arc and this works like a short and may make the meter explode, but it depends on the energy that can be drawn from the mains. The energy is fairly limited on a 230VAC 16A circuit, but in industrial settings the voltage and fuse will often be larger and then it gets very dangerous.
 

Offline dreno

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So the safety circuit of aneng or unit meter for voltage might not be safe when using mains, why? (Ok with Aneng you can accidently switch voltage and amps probes input...) Because of bad design and a lightning strike? Is there some other possibility? I mean what spikes can be in the mains if there is not a lightning strike? Does it make a difference if after the switchboard or before?

Actually why is this guy complaining that there are no fuses in the uni-t? I thought its not needed?
https://youtu.be/40YUCNYqibk?t=379
(EDIT: Couple of minutes later he says that he had a brain fart and of course there are no fuses needed ;-))

So this guy also says that these blue things are MOVs? Thats what is needed for the voltage input protection?

I dont want to make everybody happy. I just dont want my meter to explode and burn. I have a policy not to buy fluke. its too expensive. haha ;-)

« Last Edit: January 12, 2019, 09:49:13 pm by dreno »
 


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