Megaohm Meter

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fifty60

fifty60

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I need to purchase a Megaohm meter (per mandatory testing requirement for UL/IEC61010) and I am not sure where to start. I have read the documentation "A Stitch in Time" and am fairly acquainted with the actual testing, but am now trying to find a meter. My guess is that they will be expensive, so I want to make sure I purchase the correct meter.

What brands would I be looking at? Megger? Fluke? Should I buy a 500VDC or should I make sure to buy 1000VDC? Any advice/direction is appreciated.
 
fifty60 said:
I need to purchase a Megaohm meter (per mandatory testing requirement for UL/IEC61010) and I am not sure where to start. I have read the documentation "A Stitch in Time" and am fairly acquainted with the actual testing, but am now trying to find a meter. My guess is that they will be expensive, so I want to make sure I purchase the correct meter.

What brands would I be looking at? Megger? Fluke? Should I buy a 500VDC or should I make sure to buy 1000VDC? Any advice/direction is appreciated.
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What brand you buy is a matter of personal preference IMO. I have none, but I'm sure others do...

If you are testing 600V rated wire insulation, you'll need one with 1000VDC capability (FWIW 600VAC has 848V peaks).

That said, I've never seen a megger without 1000VDC capability, but I've never had to purchase one... :blink:
 
What does the standard you mentioned say about test levels? What devices will be tested?

I am not directly familiar with that standard. It is the standard combined with the list of devices ( and their input voltage requirements) that you are going to test that would determine the need.

Here is a link to one device that states it meets the requirements of the IEC61010 , realizing it may also be more than required.
http://www.productsafet.com/hipot.php
 
Smart $ said:
What brand you buy is a matter of personal preference IMO. I have none, but I'm sure others do...

If you are testing 600V rated wire insulation, you'll need one with 1000VDC capability (FWIW 600VAC has 848V peaks).

That said, I've never seen a megger without 1000VDC capability, but I've never had to purchase one... :blink:
Click to expand...

I own two 500 volt 'meggers'.
 
fifty60 said:
I need to purchase a Megaohm meter (per mandatory testing requirement for UL/IEC61010) and I am not sure where to start. I have read the documentation "A Stitch in Time" and am fairly acquainted with the actual testing, but am now trying to find a meter. My guess is that they will be expensive, so I want to make sure I purchase the correct meter.

What brands would I be looking at? Megger? Fluke? Should I buy a 500VDC or should I make sure to buy 1000VDC? Any advice/direction is appreciated.
Click to expand...

A lot depends on the features you actually need and/or want.

A very usable meter can be had used for < $200, even < $100 new if you buy Chinese.

Or you can spend upwards of $1000 and get a real fancy digital meter.

You will probably want one that can be readily calibrated though.
 
petersonra said:
You will probably want one that can be readily calibrated though.
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On that subject, how accurate do you think a megger needs to be?
In general if the leakage resistance shown by the megger is anywhere close to the leakage resistance limit you will be repairing/replacing something anyway, yes?
You would also like to be confident that the output voltage is what is expected, but even there 5% error may not be a big deal.
I suppose that in some circumstances somebody following your work may want to know that the megger was "calibrated."
 
i suspect you have to read batteries? or some form of connections in your scope?

the level of accuracy asked earlier,,, Typically needs to be able read down to uOhms.

reading battery strap connections?
Cell conductance?

Biddle
Midtronics
Fluke

we do this type of work all the time as standard practice in the DC power industry... jcassity@alpha.com if you need advise
 
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jcassity said:
the level of accuracy asked earlier,,, Typically needs to be able read down to uOhms.

reading battery strap connections?
Cell conductance?

Biddle
Midtronics
Fluke
Click to expand...
Some megohmmeters (meggers) also provide a very low resistance function, although not as good as that of a dedicated low ohm meter. But all that a megger is really required to measure is very high resistances at correspondingly high test voltages.
 
GoldDigger said:
Some megohmmeters (meggers) also provide a very low resistance function, although not as good as that of a dedicated low ohm meter. But all that a megger is really required to measure is very high resistances at correspondingly high test voltages.
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reason i posted is some people mis-use the term "megger"~ since he brought dc into it, im trying to clairfy that because it sounds
like he is actually wanting to perform conductance, resistance, Impedance and voltage.....

when dc guys say "megger" test out a dc connection or device,, they really mean uOhm... dont ask me why they do that but at the end of the day it all means a lot of labor and time documenting the data and taking responsibility for a lot of the data for future customer reference.
 
jcassity said:
reason i posted is some people mis-use the term "megger"~ since he brought dc into it, im trying to clairfy that because it sounds
like he is actually wanting to perform conductance, resistance, Impedance and voltage.....

when dc guys say "megger" test out a dc connection or device,, they really mean uOhm... dont ask me why they do that but at the end of the day it all means a lot of labor and time documenting the data and taking responsibility for a lot of the data for future customer reference.
Click to expand...
I agree, and we have had some discussions about the usefulness of meggers with low ohm ranges too for that sort of measurement. But in the OP's case, it is unlikely that the referenced UL standard cares much about low ohm measurements.
 
I like the Fluke 1587.
it doubles as a multimeter and a 1000 volt insulation tester.
i use the megger more since it is part of my multimeter.
 
Fluke

Fluke

A few things about Fluke.....
The further down the time line we have gotten, the more Fluke's quality and especially customer service has faltered.
Years ago I was able to " persuede " a Fluke Bench Tech to send me a replacement cordset for and 80i-400 current clamp which I then repaired and still have.
It now needs another cordset but " Fluke " will not let me have one......
This is because of both incompetence and resistance to allow a simple repair of a device which is still " repairable " and not necessarily cheap to replace.
The appears currently no way to get in contact with anyone in the organization that can be held accountable and take any real action.
Their manuals have gotten quite ridiculous in comparison to former generations.
Newer technology devices are not backwards compatible with older meters when they could easily be made so.
The latest Fluke product I bought which is a 376 clamp meter is a major disappointment....the main necessary feature being the flex loop
The function keys are set up like some of the other Fluke meters I own but do not work the same way, in fact, stupid would be a good description of the way it works. Instead of making it work like familiar units with the function keys doing the same thing, they reinvent the wheel so the look but do not work the same.
The quality is way down. The first 376 had to be returned due to an unresponsive keypad button.
I have used at least one of the newer generation accessory current clamps to use in my travels and it was utterly unstable and unfunctional. I don't recall the model but it was one of the large yellow AC-DC models.
I am currently looking for alternatives next time I have a metering need.
The 2 80 series units I have are still golden and should remain servicable....hopefully.
If I needed a Megger, I would look to anything " but " Fluke.
 
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