Hi, I am an electronics newbie and owing to my own
stupidity I need a new fuse for my multimeter.

Maplins say they are waiting for the right fuses
to arrive from the Far East.

My question is, do I really need the specific fuse
they recommend, or can I use another one instead?

The meter is a UT-70A (digital) by Unitrend.

The manual says get an "identical" fuse, then gives
a colon, and specifies 250V and 500mA. It also says
phi5X20(mm), which I assume just means 5mm in diameter
and 20mm long.

Maplins say the only fuse that will do is the one
with their product code N65CA.

I would be grateful if someone could tell me
whether another fuse would be OK - i.e. one that
I might actually get hold of tomorrow rather
than waiting for indefinitely! :)

I only use the meter for hobby electronics, so
if the fuse blows at 400mA instead of 500mA, that
would be OK with me. But I don't know what other
specifications it might be stupid to ignore.
Especially given that only a small number of fuses
appear to be recommended for use in multimeters.

Many thanks,

Chris

Chris Nellist wrote:

> Hi, I am an electronics newbie and owing to my own
> stupidity I need a new fuse for my multimeter.
>


Go to your nearest TV repair shop he'll supply you with one. :-)
but make it worthwhile for him, buy half a dozen.

"ben"  wrote in message 
news:QSgUe.105456$G8.22784@text.news.blueyonder.co.uk...

> Chris Nellist wrote:
>> Hi, I am an electronics newbie and owing to my own
>> stupidity I need a new fuse for my multimeter.
>>
>
> Go to your nearest TV repair shop he'll supply you with one. :-)
> but make it worthwhile for him, buy half a dozen.
>
>


And don't try to measure amps in the mains again ;-)

> Hi, I am an electronics newbie and owing to my own
> stupidity I need a new fuse for my multimeter.


Not measuring voltages on the amps range again? ;-)


> The manual says get an "identical" fuse, then gives
> a colon, and specifies 250V and 500mA. It also says
> phi5X20(mm), which I assume just means 5mm in diameter
> and 20mm long.


Very easy to find. Buy quickblow rather than surge/delay, unless you find
instructions to the contrary.


> Maplins say the only fuse that will do is the one
> with their product code N65CA.


Bollocks.

Christian.

Chris Nellist wrote:


> My question is, do I really need the specific fuse
> they recommend, or can I use another one instead?


You need the right rating. I can't think of any reason you need a 
special "multimeter fuse" (if there is such a thing) unless it is a non 
standard physical size.


> The manual says get an "identical" fuse, then gives
> a colon, and specifies 250V and 500mA. It also says
> phi5X20(mm), which I assume just means 5mm in diameter
> and 20mm long.


How about:

http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=FF00332&N=411


> Maplins say the only fuse that will do is the one
> with their product code N65CA.


Could be because they don't list 500mA 20mm glass fuses in their fuses 
section. So in a sense that may be the only one they do that is suitable.


> I would be grateful if someone could tell me
> whether another fuse would be OK - i.e. one that
> I might actually get hold of tomorrow rather
> than waiting for indefinitely! :)


I would have no worries about substituting the CPC part I linked to above.


-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

This just shows the state of Electronics and the NUMPTIES that are in
the business. Not you for blowing the fuse while measuring Amps, but
the NUMPTIES in the shop.

I've just noticed my Fluke fuse has blown this morning, can't remember
when I last measured mA. It is 5mm. dia. and 20mm. long. My Fluke says
2A. maximum on the Amps input. Just adjust yer fuse to suit the full
scale.

Chris.

mcbrien410@aol.com wrote:


> This just shows the state of Electronics and the NUMPTIES that are in
> the business. Not you for blowing the fuse while measuring Amps, but
> the NUMPTIES in the shop.


As I think I mentioned before, a recent visit to a Maplin [1] branch 
elicited a question from the sprog behind the counter: "what is a 
grommet for?" when I tried to buy one!

[1] The almost original branch in Westcliff (it moved 100yards down the 
road to new premises a few years back) where they used to employ well 
clued up electronics graduates who would think nothing of designing a 
quick circuit for the people who walked in off the street and said "how 
can I do something like....?"

-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

"John Rumm"  wrote in message 
news:4321a3fc$0$17471$ed2e19e4@ptn-nntp-reader04.plus.net...

>
> [1] The almost original branch in Westcliff (it moved 100yards down the 
> road to new premises a few years back) where they used to employ well 
> clued up electronics graduates who would think nothing of designing a 
> quick circuit for the people who walked in off the street and said "how 
> can I do something like....?"


Personally, I'm glad that our economy is no longer so crap that decent 
electronics graduates are working in chain-stores.

Will

On Fri, 09 Sep 2005 16:05:15 +0100, John Rumm  
 wrote:


> As I think I mentioned before, a recent visit to a Maplin [1] branch  
> elicited a question from the sprog behind the counter: "what is a  
> grommet for?" when I tried to buy one!


Next time ask for a hammerfour.

John Schmitt

-- 
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

> The manual says get an "identical" fuse, then gives
> a colon, and specifies 250V and 500mA. It also says
> phi5X20(mm), which I assume just means 5mm in diameter
> and 20mm long.


Might the following be suitable?
Ebay.co.uk item number 7545314889

(no connection with the seller)

Owain

On 9 Sep 2005 14:16:34 GMT, Chris Nellist wrote:


>one that I might actually get hold of tomorrow 


If you need it tomorrow, use a strand of wire. But don't repeat what
you did when you blew it!
-- 
Nigel M

"Will Dean"  wrote in message 
news:4321a7ac$0$38039$bed64819@news.gradwell.net...

> "John Rumm"  wrote in message 
> news:4321a3fc$0$17471$ed2e19e4@ptn-nntp-reader04.plus.net...
>>
>> [1] The almost original branch in Westcliff (it moved 100yards down the 
>> road to new premises a few years back) where they used to employ well 
>> clued up electronics graduates who would think nothing of designing a 
>> quick circuit for the people who walked in off the street and said "how 
>> can I do something like....?"
>
> Personally, I'm glad that our economy is no longer so crap that decent 
> electronics graduates are working in chain-stores.
>
> Will
>


I know some that work in Boots?  Mind degrees are becoming like confetti!

On Fri, 9 Sep 2005 16:18:03 +0100, "Will Dean"
 wrote:


>"John Rumm"  wrote in message 
>news:4321a3fc$0$17471$ed2e19e4@ptn-nntp-reader04.plus.net...
>>
>> [1] The almost original branch in Westcliff (it moved 100yards down the 
>> road to new premises a few years back) where they used to employ well 
>> clued up electronics graduates who would think nothing of designing a 
>> quick circuit for the people who walked in off the street and said "how 
>> can I do something like....?"
>
>Personally, I'm glad that our economy is no longer so crap that decent 
>electronics graduates are working in chain-stores.
>


You're surely not implying that our electronics industry is
flourishing, and electronics graduates can reasonably expect to get
high quality work in their own field, that went out in the '60s +'70s

http://www.wsws.org/articles/2002/jul2002/wein-j27.shtml

googling for weinstock and closure got me 15,600 hits.

DG

"Chris Nellist"  wrote in 
message news:Xns96CC9B8C71FE1pnellist@195.92.193.157...

> Hi, I am an electronics newbie and owing to my own
> stupidity I need a new fuse for my multimeter.
>
> Maplins say they are waiting for the right fuses
> to arrive from the Far East.
>
> My question is, do I really need the specific fuse
> they recommend, or can I use another one instead?
>
> The meter is a UT-70A (digital) by Unitrend.
>
> The manual says get an "identical" fuse, then gives
> a colon, and specifies 250V and 500mA. It also says
> phi5X20(mm), which I assume just means 5mm in diameter
> and 20mm long.
>
> Maplins say the only fuse that will do is the one
> with their product code N65CA.
>
> I would be grateful if someone could tell me
> whether another fuse would be OK - i.e. one that
> I might actually get hold of tomorrow rather
> than waiting for indefinitely! :)
>
> I only use the meter for hobby electronics, so
> if the fuse blows at 400mA instead of 500mA, that
> would be OK with me. But I don't know what other
> specifications it might be stupid to ignore.
> Especially given that only a small number of fuses
> appear to be recommended for use in multimeters.
>
> Many thanks,
>
> Chris


May I suggest www.farnell.com 532861   This is a ceramic fuse and so will 
cope with more nasty faults and protect you better.

"Sparks" <this@is.invalid> wrote in news:43219b36$0$38044$bed64819
@news.gradwell.net:


>
>>
>>
> 
> And don't try to measure amps in the mains again ;-) 
> 
> 

Us old Plessey AVO8 needlebenders used to ferget to go off the 50 A range
before going back to the real world of HT.

Good cutout, but not *that* good.

mike

In message , Chris Nellist 
 writes

>Hi, I am an electronics newbie and owing to my own
>stupidity I need a new fuse for my multimeter.
>
>The manual says get an "identical" fuse, then gives
>a colon, and specifies 250V and 500mA. It also says
>phi5X20(mm), which I assume just means 5mm in diameter
>and 20mm long.
>

So you just need a 20mm 500mA fuse

Does it have an "F" or a "T" on it to indicate fast or slow blow ?

Maplins should have those in stock, as for exact replacement, they're 
just covering their arses


-- 
geoff

In message <43219b71$0$1286$ed2619ec@ptn-nntp-reader02.plus.net>, John 
Rumm  writes

>Chris Nellist wrote:
>
>> My question is, do I really need the specific fuse
>> they recommend, or can I use another one instead?
>
>You need the right rating. I can't think of any reason you need a 
>special "multimeter fuse" (if there is such a thing) unless it is a non 
>standard physical size.
>
>> The manual says get an "identical" fuse, then gives
>> a colon, and specifies 250V and 500mA. It also says
>> phi5X20(mm), which I assume just means 5mm in diameter
>> and 20mm long.
>
>How about:
>
>http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=FF00332&N=411
>
>> Maplins say the only fuse that will do is the one
>> with their product code N65CA.
>
>Could be because they don't list 500mA 20mm glass fuses in their fuses 
>section. So in a sense that may be the only one they do that is 
>suitable.
>
>> I would be grateful if someone could tell me
>> whether another fuse would be OK - i.e. one that
>> I might actually get hold of tomorrow rather
>> than waiting for indefinitely! :)
>
>I would have no worries about substituting the CPC part I linked to above.
>

Cost of 5 fuses -70p ?

cost of delivery ... what, a fiver ?

(I have never placed an order under the free delivery amount, and end up 
with loads of crap which I never use)

-- 
geoff

In message <4321cbaf$0$12183$cc9e4d1f@news-text.dial.pipex.com>, James 
Salisbury  writes

>
>"Chris Nellist"  wrote in
>message news:Xns96CC9B8C71FE1pnellist@195.92.193.157...

>> I only use the meter for hobby electronics, so
>> if the fuse blows at 400mA instead of 500mA, that
>> would be OK with me. But I don't know what other
>> specifications it might be stupid to ignore.
>> Especially given that only a small number of fuses
>> appear to be recommended for use in multimeters.
>>
>> Many thanks,
>>
>> Chris
>
>May I suggest www.farnell.com 532861   This is a ceramic fuse and so will
>cope with more nasty faults and protect you better.
>

Again what's the delivery charge ?

Doh

He could prolly buy another meter for the cost of delivery from Farnell 
or CPC

-- 
geoff

raden  wrote in news:5boV6jabJfIDFwhh@ntlworld.com:


> In message , Chris Nellist 
>  writes
>>Hi, I am an electronics newbie and owing to my own
>>stupidity I need a new fuse for my multimeter.
>>
>>The manual says get an "identical" fuse, then gives
>>a colon, and specifies 250V and 500mA. It also says
>>phi5X20(mm), which I assume just means 5mm in diameter
>>and 20mm long.
>>
> So you just need a 20mm 500mA fuse
> 
> Does it have an "F" or a "T" on it to indicate fast or slow blow ?


Yes - an "F". It has got "F500mAL250V".
 

> Maplins should have those in stock, as for exact replacement, they're 
> just covering their arses


Having looked again at the catalogue, I think the GJ87U
would fit the bill. I'd be very grateful if someone could
confirm! (This would avoid me having to pay shipping costs
to Farnell's for such a cheap component).

http://www.maplin.co.uk/Module.aspx?ModuleNo=25433&doy=9m9

For some reason the Maplin's person on the phone told
me this had a voltage rating of 60V, whereas it's
actually 250V.

Not that I plan on going near potential differences
anything like as high as 60V.

Thanks to everyone for replies and help.

Chris

In message , Chris Nellist 
 writes

>raden  wrote in news:5boV6jabJfIDFwhh@ntlworld.com:
>
>> In message , Chris Nellist
>>  writes
>>>Hi, I am an electronics newbie and owing to my own
>>>stupidity I need a new fuse for my multimeter.
>>>
>>>The manual says get an "identical" fuse, then gives
>>>a colon, and specifies 250V and 500mA. It also says
>>>phi5X20(mm), which I assume just means 5mm in diameter
>>>and 20mm long.
>>>
>> So you just need a

Fast blow

>>20mm 500mA fuse
>>
>> Does it have an "F" or a "T" on it to indicate fast or slow blow ?
>
>Yes - an "F". It has got "F500mAL250V".
>
>> Maplins should have those in stock, as for exact replacement, they're
>> just covering their arses
>
>Having looked again at the catalogue, I think the GJ87U
>would fit the bill. I'd be very grateful if someone could
>confirm! (This would avoid me having to pay shipping costs
>to Farnell's for such a cheap component).


Yeah - some people seem to have lost the sense of proportion of the 
delivery costs vs the cost of such a cheap item


>
>http://www.maplin.co.uk/Module.aspx?ModuleNo=25433&doy=9m9
>
>For some reason the Maplin's person on the phone told
>me this had a voltage rating of 60V, whereas it's
>actually 250V.


I'm not an expert on fuses, but the fuse rating is a function of current 
and time. Although most 20mm fuses I see are 250v rated, I don't see the 
relevance, especially if it's hidden inside a multimeter

go for it


>
>Not that I plan on going near potential differences
>anything like as high as 60V.
>
>Thanks to everyone for replies and help.
>
>Chris
>


-- 
geoff

raden  wrote in news:H4EqyspqEgIDFw1z@ntlworld.com:


> In message , Chris Nellist 
>  writes
>>raden  wrote in news:5boV6jabJfIDFwhh@ntlworld.com:
>>
>>> In message , Chris Nellist
>>>  writes

....

>>Having looked again at the catalogue, I think the GJ87U
>>would fit the bill. I'd be very grateful if someone could
>>confirm! (This would avoid me having to pay shipping costs
>>to Farnell's for such a cheap component).
> 
> Yeah - some people seem to have lost the sense of proportion of the 
> delivery costs vs the cost of such a cheap item
> 
>>
>>http://www.maplin.co.uk/Module.aspx?ModuleNo=25433&doy=9m9
>>
>>For some reason the Maplin's person on the phone told
>>me this had a voltage rating of 60V, whereas it's
>>actually 250V.
> 
> I'm not an expert on fuses, but the fuse rating is a function of current 
> and time. Although most 20mm fuses I see are 250v rated, I don't see the 
> relevance, especially if it's hidden inside a multimeter
> 
> go for it


Many thanks!

That's me sorted!

Chris

Chris Nellist wrote:

> Hi, I am an electronics newbie and owing to my own
> stupidity I need a new fuse for my multimeter.
>


Then why not make a resetable electronic fuse? there's ample room in a
meter to fit one in circuit.

Plenty of books in the library or online for this sort of stuff.

When I used to repair TV/Videos fuses became an expensive game when it came
to locating faults and just when you thought you solved the problem the
ruddy fuse would blow.

So i made an electronic fuse to combat this till I knew the fault was
solved.

Will Dean wrote:


> Personally, I'm glad that our economy is no longer so crap that decent 
> electronics graduates are working in chain-stores.


Don't think that was the case then. Maplin was not a chain store then - 
that shop in Westcliff was the whole empire (we are talking '79/80 ish 
here - remeber the catlogue with concord on the front?).

There was usually one pre-graduate doing a "year out" type of thing - 
but the rest were electronics enthusiasts who seemed to like working there.

With regard to positions for electronics grads these days - I would say 
there are far less than in the early 80s. Software has crept into and 
replaced many of the traditional electronic engineering places, and 
analogue or high power RF work is very much reduced.

-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

John Schmitt wrote:


> Next time ask for a hammerfour.


or a dickfour... ;-)


-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

Chris Nellist wrote:


> Having looked again at the catalogue, I think the GJ87U
> would fit the bill. I'd be very grateful if someone could
> confirm! (This would avoid me having to pay shipping costs
> to Farnell's for such a cheap component).
> 
> http://www.maplin.co.uk/Module.aspx?ModuleNo=25433&doy=9m9


Yup that looks OK. It seems odd they don't list that in their 20mm glass 
fuse section...

(Still the catalogue has never been the same since they took all the 
pinouts out of the IC section! ;-)



-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

In article ,
   Chris Nellist  wrote:

> Maplins say the only fuse that will do is the one
> with their product code N65CA.


That's a 25mm (1in) Standard types are 20mm and 1 1/4in.

-- 
*Virtual reality is its own reward*

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article ,
    wrote:

> I've just noticed my Fluke fuse has blown this morning, can't remember
> when I last measured mA. It is 5mm. dia. and 20mm. long. My Fluke says
> 2A. maximum on the Amps input. Just adjust yer fuse to suit the full
> scale.


You seen the prices of genuine Fluke fuses?

-- 
*Filthy stinking rich -- well, two out of three ain't bad

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Mike,............... 'ave you seen the price of an AVO these days?
They're over 500 Quid.  I just don't know how they can knock 'em out
for that price.
Chris

mcbrien410@aol.com wrote in news:1126381292.747540.223360
@o13g2000cwo.googlegroups.com:


> Mike,............... 'ave you seen the price of an AVO these days?
> They're over 500 Quid.  I just don't know how they can knock 'em out
> for that price.


You sure? I had to have a look and prices seem to vary from about 65 to 
225?

Ther are issue variations, too.

The electric protection must have been bulletproof, but it still popped out 
a button to disconnect.

(We could straighten the needles by swinging it to get the needle up the 
other end, and at the critical moment apply reverse HT on the 50A range.) 
And if the needle did fall off, well it was an Admirality cost-plus 
contract.

Gawd help the poor taxpayer

mike

mcbrien410@aol.com wrote:

> Mike,............... 'ave you seen the price of an AVO these days?
> They're over 500 Quid.  I just don't know how they can knock 'em out
> for that price.


I 'spect they make their profit on the AVO T-shirts and flip-flops, 
children's toy electrical tool-kits in a blow moulded case, and the 
exclusive licensed men's colognes "A Touch Of Flux" and "Burnt Selenium".

Owain

mike ring wrote:


> You sure? I had to have a look and prices seem to vary from about 65 to 
> 225?


Not if you are talking the "original" model 8.

Have a look at RS stock code 653-020.... 700 quid exc VAT for the basic 
model. Another 50 if you want it calibrated! They want 109 extra on top 
  of that for the case.



-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

In article <4323af4c$0$1324$ed2619ec@ptn-nntp-reader02.plus.net>,
   John Rumm  wrote:

> Not if you are talking the "original" model 8.

> Have a look at RS stock code 653-020.... 700 quid exc VAT for the basic 
> model. Another 50 if you want it calibrated! They want 109 extra on top 
>   of that for the case.


They do, however, turn up on Ebay regularly often in mint condition. Go
for maybe 150 quid.

-- 
*Why do we say something is out of whack?  What is a whack?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Dave Plowman (News) wrote:


>>Not if you are talking the "original" model 8.
> 
> 
>>Have a look at RS stock code 653-020.... 700 quid exc VAT for the basic 
>>model. Another 50 if you want it calibrated! They want 109 extra on top 
>>  of that for the case.
> 
> 
> They do, however, turn up on Ebay regularly often in mint condition. Go
> for maybe 150 quid.


Must admit I have never quite understood the big attraction with Avos. 
Yes OK they are class 1 accuracy, and have a nice big meter movement, 
but are they really *that* good to command such a price? Or is there 
something they will do (besides keep heavy doors proped open) that I 
have missed?



-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

In article <43243f5b$0$22943$ed2619ec@ptn-nntp-reader01.plus.net>,
   John Rumm  wrote:

> > They do, however, turn up on Ebay regularly often in mint condition. Go
> > for maybe 150 quid.

> Must admit I have never quite understood the big attraction with Avos. 
> Yes OK they are class 1 accuracy, and have a nice big meter movement, 
> but are they really *that* good to command such a price? Or is there 
> something they will do (besides keep heavy doors proped open) that I 
> have missed?


They were simply the UK industry standard.
Although I do have one it rarely gets used - I've got a smaller Taylor for
things where a simple analogue meter might help diagnosis.

-- 
*Beauty is in the eye of the beer holder...

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In message , "Dave Plowman (News)" 
 wrote

>In article <43243f5b$0$22943$ed2619ec@ptn-nntp-reader01.plus.net>,
>   John Rumm  wrote:
>> > They do, however, turn up on Ebay regularly often in mint condition. Go
>> > for maybe 150 quid.
>
>> Must admit I have never quite understood the big attraction with Avos.
>> Yes OK they are class 1 accuracy, and have a nice big meter movement,
>> but are they really *that* good to command such a price? Or is there
>> something they will do (besides keep heavy doors proped open) that I
>> have missed?
>
>They were simply the UK industry standard.


I think the operative word is 'were'.
They were outclassed on performance twenty years ago.

The price probably doesn't reflect the quality of the meter but the cost 
of the calibration and the tractability back to standards.

The average 'certified' electrician will be paying 100s to get their 
existing equipment calibrated each year.

-- 
Alan
mailto:news2me_a_2003@amacleod.clara.co.uk

In article ,
   Alan  wrote:

> >> Must admit I have never quite understood the big attraction with Avos.
> >> Yes OK they are class 1 accuracy, and have a nice big meter movement,
> >> but are they really *that* good to command such a price? Or is there
> >> something they will do (besides keep heavy doors proped open) that I
> >> have missed?
> >
> >They were simply the UK industry standard.

> I think the operative word is 'were'.
> They were outclassed on performance twenty years ago.


For many AC measurements - or anything which required a high impedance
device - many more years earlier. I've got a homemade (Heathkit) valve
voltmeter which is over 30 years old. 


> The price probably doesn't reflect the quality of the meter but the cost 
> of the calibration and the tractability back to standards.


It's just the cost of making something so old fashioned.


> The average 'certified' electrician will be paying 100s to get their 
> existing equipment calibrated each year.


I've got some ways of calibrating DVMs, and they don't drift that much -
if well made. In some ways, calibration is a bit like CORGI etc
membership. Just to satisfy the suits.

-- 
*All those who believe in psychokinesis, raise my hand *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In message , "Dave Plowman (News)" 
 wrote


>
>I've got some ways of calibrating DVMs,


While you may have some accurate ways of calibrating (or checking the 
calibration of) a multi-meter I guess the average electrician doesn't. 
Was that resistance measurement really 2 ohms or  was it actually 4 ohms 
but with a partially fried ranging component?


>and they don't drift that much -
>if well made.


If not subjected to (accidental) abuse the underlying DVM part of the 
equipment may not drift that much in a well made piece of modern 
equipment. Any form of accidental abuse may outwardly give an indication 
that no damage has been done because the meter still gives a reading but 
one or more of the ranges may be widely inaccurate. How many 
electricians are proclaiming installations are safe and are writing 
certificates while still using equipment that has never been checked for 
accuracy since they purchased it.


> In some ways, calibration is a bit like CORGI etc
>membership. Just to satisfy the suits.


In some respects yes,  if taken to the extreme ,  but also regard a 
regular calibration in the same way a road vehicle MOT test. Many faults 
are not identified until someone else checks out the equipment.

-- 
Alan
mailto:news2me_a_2003@amacleod.clara.co.uk

In message , Alan 
 writes

>In message , "Dave Plowman (News)" 
> wrote
>
>>
>>I've got some ways of calibrating DVMs,
>
>While you may have some accurate ways of calibrating (or checking the 
>calibration of) a multi-meter I guess the average electrician doesn't. 
>Was that resistance measurement really 2 ohms or  was it actually 4 
>ohms but with a partially fried ranging component?
>

How often would a sparkie want to measure more than whether 230V was 
there or not with a DVM ?


-- 
geoff

In message , raden  
wrote

>In message , Alan 
> writes
>>In message , "Dave Plowman (News)" 
>> wrote
>>
>>>
>>>I've got some ways of calibrating DVMs,
>>
>>While you may have some accurate ways of calibrating (or checking the 
>>calibration of) a multi-meter I guess the average electrician doesn't. 
>>Was that resistance measurement really 2 ohms or  was it actually 4 
>>ohms but with a partially fried ranging component?
>>
>How often would a sparkie want to measure more than whether 230V was 
>there or not with a DVM ?
>


Do you mean that they don't actually do earth bonding tests etc. It may 
not be performed with the 4 LIdl special offer DVM but it should be 
with equipment that is calibrated if they are going to issue a 
certificate saying that the installation is safe..



-- 
Alan
mailto:news2me_a_2003@amacleod.clara.co.uk

"Alan"  wrote in message 
news:n3KJBdGfMhJDFwpw@amacleod.clara.co.uk...


>
> In some respects yes,  if taken to the extreme ,  but also regard a 
> regular calibration in the same way a road vehicle MOT test. Many faults 
> are not identified until someone else checks out the equipment.
>


Not sure if that's a good analogy.  A good car mechanic will have some 
sympathy with the car and sort important things out before an MOT.  Recovery 
vehicles are exempt from MOTs.

In article ,
   Alan  wrote:

> If not subjected to (accidental) abuse the underlying DVM part of the 
> equipment may not drift that much in a well made piece of modern 
> equipment. Any form of accidental abuse may outwardly give an indication 
> that no damage has been done because the meter still gives a reading but 
> one or more of the ranges may be widely inaccurate. How many 
> electricians are proclaiming installations are safe and are writing 
> certificates while still using equipment that has never been checked for 
> accuracy since they purchased it.


Well, yes. But assuming that damage happened just after annual calibration
and certification there could be many many installations not checked
correctly.

At one time the accurately calibrated speedometers in police traffic cars
where checked for calibration daily...

-- 
*Experience is something you don't get until just after you need it.*

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In message , Alan 
 writes

>In message , raden  
>wrote
>>In message , Alan 
>> writes
>>>In message , "Dave Plowman (News)" 
>>> wrote
>>>
>>>>
>>>>I've got some ways of calibrating DVMs,
>>>
>>>While you may have some accurate ways of calibrating (or checking the 
>>>calibration of) a multi-meter I guess the average electrician 
>>>doesn't. Was that resistance measurement really 2 ohms or  was it 
>>>actually 4 ohms but with a partially fried ranging component?
>>>
>>How often would a sparkie want to measure more than whether 230V was 
>>there or not with a DVM ?
>>
>
>Do you mean that they don't actually do earth bonding tests etc. It may 
>not be performed with the 4 LIdl special offer DVM but it should be 
>with equipment that is calibrated if they are going to issue a 
>certificate saying that the installation is safe..
>




How many of them would even know to null out the resistance of the 
probes ?


-- 
geoff

On Fri, 09 Sep 2005 21:42:28 GMT, raden  wrote:


>In message , Chris Nellist 
> writes
>>raden  wrote in news:5boV6jabJfIDFwhh@ntlworld.com:
>>
>>> In message , Chris Nellist
>>>  writes
>>>>Hi, I am an electronics newbie and owing to my own
>>>>stupidity I need a new fuse for my multimeter.
>>>>
>>>>The manual says get an "identical" fuse, then gives
>>>>a colon, and specifies 250V and 500mA. It also says
>>>>phi5X20(mm), which I assume just means 5mm in diameter
>>>>and 20mm long.
>>>>
>>> So you just need a
>
>Fast blow
>
>>>20mm 500mA fuse
>>>
>>> Does it have an "F" or a "T" on it to indicate fast or slow blow ?
>>
>>Yes - an "F". It has got "F500mAL250V".
>>
>>> Maplins should have those in stock, as for exact replacement, they're
>>> just covering their arses
>>
>>Having looked again at the catalogue, I think the GJ87U
>>would fit the bill. I'd be very grateful if someone could
>>confirm! (This would avoid me having to pay shipping costs
>>to Farnell's for such a cheap component).
>
>Yeah - some people seem to have lost the sense of proportion of the 
>delivery costs vs the cost of such a cheap item
>
>>
>>http://www.maplin.co.uk/Module.aspx?ModuleNo=25433&doy=9m9
>>
>>For some reason the Maplin's person on the phone told
>>me this had a voltage rating of 60V, whereas it's
>>actually 250V.
>
>I'm not an expert on fuses, but the fuse rating is a function of current 
>and time. Although most 20mm fuses I see are 250v rated, I don't see the 
>relevance, especially if it's hidden inside a multimeter


The 250V is the maximum that the fuse is rated to break.

At voltages above it's rating a fuse may arc and continue to pass
current instead of opening and clearing the fault.

If a 32V fuse (as used in cars) is fitted, the meter is set to
current, the leads are connected across 240V, and the fuse did not
clear but arced, serious personal injury or death could result.


>
>go for it
>
>>
>>Not that I plan on going near potential differences
>>anything like as high as 60V.
>>
>>Thanks to everyone for replies and help.
>>
>>Chris
>>

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In message , Jim Michaels 
 writes

>>>For some reason the Maplin's person on the phone told
>>>me this had a voltage rating of 60V, whereas it's
>>>actually 250V.
>>
>>I'm not an expert on fuses, but the fuse rating is a function of current
>>and time. Although most 20mm fuses I see are 250v rated, I don't see the
>>relevance, especially if it's hidden inside a multimeter
>
>The 250V is the maximum that the fuse is rated to break.
>
>At voltages above it's rating a fuse may arc and continue to pass
>current instead of opening and clearing the fault.
>
>If a 32V fuse (as used in cars) is fitted, the meter is set to
>current, the leads are connected across 240V, and the fuse did not
>clear but arced, serious personal injury or death could result.
>


Err ... how exactly ?

If you're measuring something with a DVM, you're only either touching 
the probes and/or the dial. The fuse is there to protect the DMM guts

-- 
geoff

On Wed, 14 Sep 2005 19:52:21 GMT, raden  scrawled:


>>If a 32V fuse (as used in cars) is fitted, the meter is set to
>>current, the leads are connected across 240V, and the fuse did not
>>clear but arced, serious personal injury or death could result.
>>
>
>Err ... how exactly ?
>
>If you're measuring something with a DVM, you're only either touching 
>the probes and/or the dial. The fuse is there to protect the DMM guts


Which could explode and kill and\or mame humans in the vicinity if the
correct fuse isn't fitted, possibly.....
-- 
Stuart @ SJW Electrical

Please Reply to group

In message , Lurch 
 writes

>On Wed, 14 Sep 2005 19:52:21 GMT, raden  scrawled:
>
>>>If a 32V fuse (as used in cars) is fitted, the meter is set to
>>>current, the leads are connected across 240V, and the fuse did not
>>>clear but arced, serious personal injury or death could result.
>>>
>>
>>Err ... how exactly ?
>>
>>If you're measuring something with a DVM, you're only either touching
>>the probes and/or the dial. The fuse is there to protect the DMM guts
>
>Which could explode and kill and\or mame humans in the vicinity if the
>correct fuse isn't fitted, possibly.....


Yeah - inside a DVM case - really

it's not a bloody landmine, it's a glass tube, stuck inside a plastic 
case

-- 
geoff

On Thu, 15 Sep 2005 00:10:41 GMT, raden  wrote:


>In message , Lurch 
> writes
>>On Wed, 14 Sep 2005 19:52:21 GMT, raden  scrawled:
>>
>>>>If a 32V fuse (as used in cars) is fitted, the meter is set to
>>>>current, the leads are connected across 240V, and the fuse did not
>>>>clear but arced, serious personal injury or death could result.
>>>>
>>>
>>>Err ... how exactly ?
>>>
>>>If you're measuring something with a DVM, you're only either touching
>>>the probes and/or the dial. The fuse is there to protect the DMM guts
>>
>>Which could explode and kill and\or mame humans in the vicinity if the
>>correct fuse isn't fitted, possibly.....
>
>Yeah - inside a DVM case - really
>
>it's not a bloody landmine, it's a glass tube, stuck inside a plastic 
>case


Ignorance can be fatal

When checking out a meter tail.

240V x  5,000a =  1.2 MegaJoules/second.

This is equal to 409grams of TNT exploding per second.

Which is equal to a Claymore Landmine exploding every 1.6 seconds.

The plastic case will make very effective shrapnel!
Not to mention the burns from the arc flash and the spray of molten
copper from the test leads.

For more information...

http://www.ferret.com.au/articles/ca/0c02ebca.asp
http://www.arcadvisor.com/faq/what_are_arcflash_hazards.html
http://www.bussmann.com/library/indcon/Electrical%20safety%20and%20arc%20flash.pdf
http://www.galco.com/techdoc/FLKE/Test_Instruments_PPE_APP.pdf

and starting on page 5...
http://www.eh.doe.gov/paa/oesummary/oesummary2004/oe2004-14.pdf

Safety is not a trivial issue.
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