Megger

[Heyoiu]

Hello to all you fine Sparkies,

Can someone please advise me on what type of Megger testing  kit to purchase for testing and inspecting.

Also i have heard that C.K tools as in whole kit, are an good buy for a beginner, if so what sort of costs am i looking at?

Currently studying Level 3 at college, so professional  experienced advise will be greatly welcomed.

thanks 

 

[Andy™]

something that does all the required tests. any advertised as '17th edition tester' will be adequate

costs vary a lot between the different manufacturers. have a look at isswww.co.uk

 

[phil d]

I have a Metrel MFT and a DiLog, both are pretty decent and not too expensive, I actually picked up the DiLog for £100 on ebay, it needed calibration which cost me £50 but hey wow, it was like new and for that kind of money it was a bargain.

You don't want to be spending loads of money at first, find out what you need and then buy it, for example, apart from screwdrivers and cutters and test lamps, you'll need different gear depending on what you are working on. I served my time in industry and it was years before I owned a bolster chisel, on the other hand I did own a conduit bender and stocks and dies!

I used to buy a piece of kit every week when I got paid, started off with the small stuff, then as my wages increased I bought more expensive kit.

Multimeters are an interesting one, some people think that an expensive one is better than a cheaper one, in some cases it is true, they have more features, but do you need them? I have a Fluke and it does all sorts of things, but most of them are used fairly infrequently, I'd start off with a basic meter and go from there, learn to "drive" a basic meter before buying a more expensive one. Quite often an experienced electrician will find a fault with a meter costing say a tenner when a less experienced guy with a meter costing several hundred quid has failed.

The elex shows can throw up some good deals, I recently purchased a large set of Starret holesaws for £50, at one of these shows, they retail at around £100, quite a saving I'm sure you'll agree.

 

[Sidewinder]

Whatever you do, only buy known brand test equipment and leads.

If these items go wrong, you might not live to tell the tale.

In deference to PhilD's post, cheap DMM's can be decidedly dangerous, I have seen a few go pop big time.

I have a several Flukes, I can put the meter on Ohms and try to measure voltage up to 400V between leads, and they just beep at me.

Some cheam DMM's will simply explode in that scenario.

Also the Flukes I have will simply blow the fuse if used to measure a voltage when set up for current, again cheap no brand meters will often simply explode.

Your life, your choice.

 

[apprentice87]

I had a DMM once.. i had had it since about 1981 and i thought the world of it [yes, i know i am weird] Once in a moment of absent mindedness, when it was set to the current setting, [20a max] I went and connected it across 2 phases of a 400v supply.. [23,000a max!!]

I can certainly vouch for the fact that you will poo yourself... AND the meter survived!!!

Not only did it trip the 16A mcb protecting the circuit, but also the 80A MCCB protecting the submain.. [so much for discrimination!!]

Some time later, i went and decided i would measure the OCV of my AC tig set.. Hmmm, yes, i did forget about the HF... That killed the meter....

john..

 

[phil d]

Whatever you do, only buy known brand test equipment and leads.

If these items go wrong, you might not live to tell the tale.

In deference to PhilD's post, cheap DMM's can be decidedly dangerous, I have seen a few go pop big time.

I have a several Flukes, I can put the meter on Ohms and try to measure voltage up to 400V between leads, and they just beep at me.

Some cheam DMM's will simply explode in that scenario.

Also the Flukes I have will simply blow the fuse if used to measure a voltage when set up for current, again cheap no brand meters will often simply explode.

Your life, your choice.

When I said a cheap meter I meant something like an extech or similar for around the 50 quid mark, rather than a 400 quid Fluke. I'd never trust one of these ebay specials for a tenner, it just depends on what you are doing, I have some very expensive kit, I  also have some cheaper stuff for day to day use, it all depends on what you are doing.

 

[Sidewinder]

When I said a cheap meter I meant something like an extech or similar for around the 50 quid mark, rather than a 400 quid Fluke. I'd never trust one of these ebay specials for a tenner, it just depends on what you are doing, I have some very expensive kit, I  also have some cheaper stuff for day to day use, it all depends on what you are doing.

I don't use any "cheap" test equipment, normally, if I am looking at a fault it means that the muppets have been first, or the cheap kit won't cut it, e.g. a lot (most) of the cheap meters are not good on PWM drives, so no use to me at all, because I don't know when I am going to meet one, or not.

Next, the cheaper the meter, the lower the input impedance normally, great for eliminating stray voltages, but, I have a gizmo for that, however when I am going down to board level, you can't increase the input impedance of a meter easily.

Also, I don't see the point in carrying cheap tat, and good kit, so I only carry good kit.

 

[phil d]

I don't use any "cheap" test equipment, normally, if I am looking at a fault it means that the muppets have been first, or the cheap kit won't cut it, e.g. a lot (most) of the cheap meters are not good on PWM drives, so no use to me at all, because I don't know when I am going to meet one, or not.

Next, the cheaper the meter, the lower the input impedance normally, great for eliminating stray voltages, but, I have a gizmo for that, however when I am going down to board level, you can't increase the input impedance of a meter easily.

Also, I don't see the point in carrying cheap tat, and good kit, so I only carry good kit.

Exactly, it's horses for courses, but if you are just using a meter for basic stuff, continuity, checking for a voltage and such then is it worth paying 3 or 4 hundred quid? probably not. I have a modestly priced instrument that "lives" in my car, it's good enough for day to day usage, then I have my more expensive meter for when I need it. I generally know what I'm going out to, so it's not a problem, if I'm going to say, an alarm fault, the cheaper one will do, if it's a fault on a plc or a machine with electronic controls, then out comes the dear one.

 

[Sidewinder]

The thing is phil, if the cheap meter fails due to poor design, you'll be just as dead.

I'd rather ensure that I stay alive by not using cheap tat, plus it is doubtful that it would pass calibration after the first year so buying new every year is just a waste.

I have a 20+yr old Fluke that has passed calibration every time it has been for cal, without any adjustment.

I'm currently looking at a spend of £2-4k depending on who I go with, the spec I decide on and the deal I can cut, on one machinery tester for electrical testing.

I currently have about 30 test meters of different types, and none will do all the tests I need in one box, so it would mean at least 5 meters to do what this one can do.

 

[phil d]

The thing is phil, if the cheap meter fails due to poor design, you'll be just as dead.

I'd rather ensure that I stay alive by not using cheap tat, plus it is doubtful that it would pass calibration after the first year so buying new every year is just a waste.

I have a 20+yr old Fluke that has passed calibration every time it has been for cal, without any adjustment.

I'm currently looking at a spend of £2-4k depending on who I go with, the spec I decide on and the deal I can cut, on one machinery tester for electrical testing.

I currently have about 30 test meters of different types, and none will do all the tests I need in one box, so it would mean at least 5 meters to do what this one can do.

Exactly, it's horses for courses, but lets be honest if the average spark is just using a meter for straight basic tests, i.e is there continuity, and whats the voltage, is it 110, 230 or 400, then how many get it calibrated annually?  not many I'll bet. Where you are looking for a difference of 1 or 2 volts then accuracy is critical if it's just a "go or no go" then it's not exactly mission critical.

 

[ProDave]

Exactly, it's horses for courses, but lets be honest if the average spark is just using a meter for straight basic tests, i.e is there continuity, and whats the voltage, is it 110, 230 or 400, then how many get it calibrated annually?  not many I'll bet. Where you are looking for a difference of 1 or 2 volts then accuracy is critical if it's just a "go or no go" then it's not exactly mission critical.

The argument is not so much about calibration, but about safety.

I am not suggesting you try this, but switch a Fluke meter to ohms, and connect it across 240V. Then do the same with a £5 multi meter.

Which one do you think will let it's smoke out. Which one do you think might actually hurt you. Which one do you think will take it in it's stride and live to work another day still nice and safe?

 

[Sidewinder]

Exactly, it's horses for courses, but lets be honest if the average spark is just using a meter for straight basic tests, i.e is there continuity, and whats the voltage, is it 110, 230 or 400, then how many get it calibrated annually?  not many I'll bet. Where you are looking for a difference of 1 or 2 volts then accuracy is critical if it's just a "go or no go" then it's not exactly mission critical.

1 or 2V!

In the days of analogue controls, we used to null to +/- 0.005V!

Seriously, cheap meters are much more dangerous than they are limited in accuracy.

Take today, I had just left a customer/supplier, about 45 minutes from home at 4pm, hoping to miss the bulk of the traffic.

Phone goes, my laundry customer, I knew what machine was down before I answered, their tunnel wash, and almost certainly full.

So, I agree to call there “on the way back”, they are there till 6pm anyway because of other issues.

I get there and there are some screwy things going on with the fwd/rev on the tunnel.

So I get out my trusty Fluke 87 and start working my way through the circuit, now I’m not worried whether I have 230 or 240V AC exactly, as long as it is there or there abouts on the contactor coils etc.

However, I have one of their maintenance guys & their “production manager” standing watching me.

So, I am working my way through the circuit live and dead testing as appropriate.

I’ve just done some dead testing so measuring a couple of contactor coil continuities, and we switch the machine back on.

It’s late, I’m tired, I’ve been at work for 10 hours already today both hard physical graft, and, technical stuff too.

So, I make the error of not switching the meter from Ohms to AC V before I check for 3ph across the top of a contactor.

What does the Fluke do?   Flash the display at me and show 0.00.  So I correct the setting and carry on.  No damage to the meter, no damage to me.

OK, yes my fault, it’s called a lapse in technical terms.  However, the Fluke is designed to cope @ £400 ish.  Would a £5 - £10 meter really cut the mustard and protect you from a lapse?

I doubt it.

So for me, it’s not about accuracy, & repeatability, which are, as you will know different.  It is also about the readings you get when things are not right, allowing for lapses in concentration without killing you for example.

 

[Lurch]

Check out EEVBlog on Youtube for loads of meter teardowns/reviews/failure mode tests.

There's a decent bit of video I watched a while ago on this very subject of meters across mains when set to ohms, was an excerpt from a Fluke factory tour IIRC. Showed some cheap meters just exploding when stuck across 230V when set on resistance.

 

[kerching]

Remember that machinery , as well as electricity , will not stop when something goes wrong ( short circuit, limb stuck in mechanism etc) just because you scream and it will carry on hurting

 

[apprentice87]

It is also about the readings you get when things are not right, allowing for lapses in concentration without killing you for example

And i can tell you from experience that If you have a cheap meter, and, due to tiredness, you have it set on the wrong setting, you will be lucky to survive... As i said, i did it once and it was not a nice experience at all...

As Paul says, do it on my Megger and it just tells you that you have made a mistake and you live to make another one!!

I am only an amateur, and apart for my DMM [that is now only used for low voltage "vehicle" type stuff] every bit of kit i have is by megger [probably why i am still alive!!]

john..

 

[Andy™]

think i may have to go get a cheap meter and stick it across 400v on ohms just to see what happens... from a safe distance...

 

[ProDave]

think i may have to go get a cheap meter and stick it across 400v on ohms just to see what happens... from a safe distance...

Give us the you tube link when you have done it.

In the old days the meter cut out would have popped up on the Avo 8

 

[Andy™]

think ill get one of these

https://www.screwfix.com/p/lap-mas830b-digital-multimeter-600v/75337

only £7.43.

so, do i ram 230v or 400v into it?

 

[kerching]

the bigger the better......make sure you video it

 

[Blue Duck]

400v make sure you are measuring amps  with the wrong leads