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  #1519408 25-Mar-2016 01:43
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IMO go for a good one like a fluke or agilent or similar, and get multiple $20-30 ones for hobby non mains work. Several can be handy for checking the input and output of a DC-DC converter at the same time, and means you have a second one to verify against. And for using where dropping etc may be a concern.

 

I have not had a problem with the accuracy of the cheap $22 ones from bunnings when used on DC or 50Hz AC, its the higer frequancy and the non sine waves where the good true RMS etc is worth it.

 

 





Richard rich.ms



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  #1519645 25-Mar-2016 14:35
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In what situations do you need to measure millivolts / milli amps?

Basically I am at this stage,
Tenma (uni-t 139c), really good feature range, mainly large capacitance range and mv + ma scale, but not sure if I would feel 100% confident using it for mains voltage. Would rather spend another $40 ontop of the $80 price and get the fluke 107. However might be able to get one for $50

Fluke 107, not true rms, I probably don't need true rms? apparently not made for electronics due to limited milli amp+volt range.

Hioki/bryman, both at $170,
Not saying I won't go with the brymen, but part of me does not feel sold. I think due to the back light issue and brymens cheap looking website which I know is no relation to the quality of the meter.

Hioki, apparently comparable to fluke, does not have ac milli volt range, but do I even need it


 
 
 
 


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  #1519804 25-Mar-2016 19:46
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Many analog controls use mA signals. 0-20mA and 4-20mA are common ranges.

Thermocouples use mV




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  #1520638 28-Mar-2016 07:54
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Thanks for all the info, I narrowed it down to the brymen 253 and hioki 4256.

 

Think I am going to go with the hioki due to the brymen backlight issue and the fact it is not currently in stock. The Hioki does not have a mv AC range of sub 1 uf cap range but hopefully the next level resolutions are enough. 


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  #1520651 28-Mar-2016 09:10
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I've only seen a couple of Hoki meters (an insulation tester and a clamp meter), but the seemed like quite good units. The only quirk was the batteries in the clamp were button cells.

The Hoke you're looking at takes AAA batteries.

I missed the previous question about AC mV ranges. I don't think you'll need AC mV ever, my examples were DC mA / mV.

It looks like a nice meter, I say go for it.




Location: Dunedin

 




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  #1524768 2-Apr-2016 19:14
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Now I have the meter I have some stupid questions about measuring mains voltage. But would rather ask than guess?

 

1) If I put the +ve meter prong into the phase and leave the negative disconnected I get a reading of 13v AC @ 50hz, what would happen if I touch the negative prong of the meter?

 

2) Are you suppose to connect/disconnect in a certain order e.g Neutral first? 

 

3) Can you measure between phase and earth?

 

4) What happens if you stick the -ve into phase and +ve into neutral? does it just read -230v?


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  #1524773 2-Apr-2016 19:29
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2) no doesnt matter

 

3) yes, when on the volts scale the internal resistance of the meter is super high (think 10Mohm)

 

4) if you reverse the probes you get a negative reading on the voltage scales


 
 
 
 


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  #1524775 2-Apr-2016 19:37
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1 . would depend on the input impedance of the meter. That it is showing 13v with it floating means its probably high impedance, so you should just see that voltage go up.

 

but more importantly, WHY THE HELL ARE YOU THINKING OF TOUCHING A WIRE THAT GOES THE THE MAINS!?

 

4 . No, it will still show 230v as there is no polarity for AC without something to reference it to, one AC signal could be -230v when compared to another one, but if you are just measuring a single waveform then it cannot be negative.





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  #1524786 2-Apr-2016 19:47
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richms:

 

4 . No, it will still show 230v as there is no polarity for AC without something to reference it to, one AC signal could be -230v when compared to another one, but if you are just measuring a single waveform then it cannot be negative.

 

 

Pretty sure that just depends on what you use as a reference when it comes to AC


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  #1524887 2-Apr-2016 22:10
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Nope. Your meter wont ever show negative for AC volts.

 

On AC ranges , any DC bias will be removed and only any AC variations will be shown.

 

 

 

3. You can measure volts between phase and earth, and have to for certain checks. Don't ever try to measure resistance between these though. A good meter might survive with blown fuses, a cheapie might not.

 

So you got the Hioki in the end? Tell us where you got the best price, for the record.


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  #1524897 2-Apr-2016 22:41
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It doesn't matter which way round the leads are when testing mains. It is perfectly safe and actually often necessary to test to earth as well.
When testing sockets, it is important to insert a lead into the neutral or earth first though. This is because modern sockets have shutters in them and the phase one doesn't open by itself.

ALWAYS treat the other lead as live. Generally speaking touching it is realitivly safe, however if you have the leads connected for current measurement, it is far from safe. A failure within the meter is also possible. Keep good habits so that when there is a problem, you stay alive.


Jase2985:

richms:


4 . No, it will still show 230v as there is no polarity for AC without something to reference it to, one AC signal could be -230v when compared to another one, but if you are just measuring a single waveform then it cannot be negative.



Pretty sure that just depends on what you use as a reference when it comes to AC


Meters do not show polarity for AC. There is no polarity.

The phase sine wave by its very nature is both positive and negative. If you are testing in a situation where phase is always more positive (or negative) than your reference, you aren't measuring AC. That would be, by definition, a DC measurement.



When a meter gives you a value, all it is saying is that one lead is [value] more positive than the other lead. It is up to the user to interpret the meaning of the reading.




Location: Dunedin

 


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