Fluke Mft Voltage Measurement

[Robin Spark]

Right ok

I dont want to start a debate on which tester is best, but on the Fluke 1654b when measuring voltage and you have the plug socket adaptor lead inserted you can toggle between L-N, L-E and N-E.

However, if you set the function to test for L-N but disconnect the neutral lead it still gives you the reading for L-PE?

I find that a bit puzzling???

 

[steptoe]

do you know how to test/use your tester?

nothing puzzling about it, your tester knows you have removed a lead.

 

[Robin Spark]

Aha but does it?

I think its very misleading when you have no neutral on the circuit but it still shows L -N voltage as 246v when you use the plug lead adaptor.

It also does not show any of those incorrect polarity arrows either.

 

[Sidewinder]

Well if the L-E voltage is 230, then the L-N is gonna be about the same.

Not sure what you're getting at Robin?

 

[apprentice87]

Perhaps, it is like a safety thing, ok, so the meter knows there is a lead disconnected when you are testing L/N

Perhaps, the makers decided that they would make the meter give a reading L/E instead, so as to stop you going, "Ho hum, L/N dead, i think i will stick my finger in there, Zap!!!

Yes i do know that you would not just test L/N for obvious reasons, but we live, and so do the meter makers, in a work of health and safety gone mad!

john

 

[steptoe]

Right ok

I dont want to start a debate on which tester is best, but on the Fluke 1654b when measuring voltage and you have the plug socket adaptor lead inserted you can toggle between L-N, L-E and N-E.

However, if you set the function to test for L-N but disconnect the neutral lead it still gives you the reading for L-PE?

I find that a bit puzzling???

Aha but does it?

I think its very misleading when you have no neutral on the circuit but it still shows L -N voltage as 246v when you use the plug lead adaptor.

It also does not show any of those incorrect polarity arrows either.

make up your mind

what voltage is it showing you?

I use one of these testers on a daily basis and I have no idea what you are on about.

 

[Robin Spark]

Steps i just replied but my post has gone missing!!!

I'll type it again just give a moment

Sorry guys for taking so long to reply back!

Just been mega busy at the weekend trying to keep everyone pleased at home and visitors etc!

Well what stumped me was some friends have just moved into their new home and they gave me a call as their electric cooker wasnt working.

Me not intending to do any work this weekend just took minimal of tools and said to the mrs "oh it will just be a quick visit". (Haha I hear you all say)

So i get to friends new house and have a look around, noting that the consumer unit is totally innaccessible due to being right up the back corner of the garage and their is a whole houseful of their contents in their! So as you can imagine Im a bit restricted to what I could do

Anyway back in the kitchen I plug my fluke mft into the socket on the cooker control switch and have 245v L-N and L-E, with 8.9v N-E. So i presumed everything is ok at that point. Then I pull the cooker out and get same voltage L-E but nothing between L-N.

So now Im thinking the problem lies between either faulty cooker switch or maybe a dodgy junction box on load side of switch to the cooker.

After a bit of discussion with my friend he decides instead of moving everything out the garage (i havent got much time to stay as the boss wants to go to blxxdy merry hill shopping) then he is going to climb over all his stuff to the consumer unit with me watching and his mrs shouting at him to be careful and not break anything :slap .

Luckily the breaker for the cooker is marked up and circuit isolated.

On removing cooker switch (thinking Im going to check connections and test continuity of switch and cable to cooker) I found the neutral conductor was loose in the back box - this was the supply cable.   So after reconnecting this everything and all of the other connections which my daughter could have done up tighter made everything ok.

Later that day back at home, I purposely disconnected a neutral from a socket and with the 3 lead plug tester it still shows a L-N reading.  However it wont let you do a loop test (error 4) for L-N and it comes up >2000 for L-E.

Hope this all makes sense.

 

[steptoe]

yer, ok,

but check what exactly you are measuring voltage across,

I'll bet default is L-E

 

[Robin Spark]

Yes,

its just that even the manual says you can plug in the 3 lead adaptor and then get measurements L-N, L-E and N-E.

Try it on yours when you get chance  and let me know if you can.

As a side note Im going to pm Megger Mark and see if he knows anything or will speak to Fluke.

 

[steptoe]

yes, you can toggle between what measurements you take, but IIRC it defaults to L-E unless you change it.

 

[Robin Spark]

yes, you can toggle between what measurements you take, but IIRC it defaults to L-E unless you change it.

Yes I know what you are saying but when you do toggle through it should really give you the same readings as when you are using the two individual test leads and manually checking between each set of terminals (well thats what i thought???)

However, in hindsight I should have done a loop test at the cooker switch which would have shown a fault on the supply side of the switch.

 

[ISSWWW]

In essence the tester is doing what Fluke intended it to do, it has no reference if the N is pulled and although the indicator remains the same it default to L/PE.

I haven't checked with them but i think it happens for two reasons:

A/ Safety

B/ Without anything to reference it to it's all it can do

The L & PE terminals do have some kind of firm ware sensor that informs the tester if these are disconnected, i guess this has something to do with two wire testing.

In the user manual it states that all three leads should be used when performing this test, and i guess the question might be why wouldn't you?

 

[Robin Spark]

Thanks Megger Mark for clarifying this,

something to keep in mind and yes I think the normal two wire testing is the more reliable method for checking voltage across all terminals.

So my misunderstanding to the limitations of the tester and so not going to use the three wire method again unless its for Zs.