EDAboard.com | EDAboard.de | EDAboard.co.uk | WTWH Media

Need fuses for Multimeter

Ask a question - edaboard.com

elektroda.net NewsGroups Forum Index - Electronics Components - Need fuses for Multimeter

Goto page Previous  1, 2

Tom Del Rosso
Guest

Thu Feb 01, 2018 1:48 am   



oldschool_at_tubes.com wrote:
Quote:

Until Radio Shack closed their doors, they DID have a decent selection
of fuses, switches, and certain other parts. They were lacking with
capacitors and semiconductors though. Yea, their prices were a little
high, but they were convenient....


Since it is for a meter, and because you had trouble finding it, I
assumed it was an HRC and not a common fuse. Sorry.

Ralph Mowery
Guest

Thu Feb 01, 2018 1:50 am   



In article <2i647dla33h4gegvdpqbqn6k5ugu9qeein_at_4ax.com>,
oldschool_at_tubes.com says...
Quote:
Fuses that have a higher voltage rating are fine to use in the low
voltage applications. They only work on the curent. In those
inexpensive meters with fuses only rated for 250 volts, they could be
dangerous at higher voltages. We were shown a trainging film by the
Fluke salesmen. They showed what could hapen if you had a low voltage
fuse and had the meter set for ohms or amps and put it across a 480 volt
line with plenty of curent. The fuse would arc over and the leads would
melt down. You would too if you were holding the leads. They make some
special fuses for them to get the higher CAT ratings.


Ok, that makes sense. Apparently the element inside the fuse must melt
for a wider gap on higher voltage rated fuses. Which would occur because
of the type of metal used and/or shape of the wire. I have seen fuses
with that element looking wavy, so I suppose that has something to do
with it. This is all mostly just a guess, but something has to make that
gap wider to prevent arc-over.

I can see arcing at voltages above 250 V. I have worked on lots of old
tube tv sets, and have seen the B+ high voltage jump across tube socket
pins and other places. Most of the time the voltages were from 300 volts
up to nearing 600 volts. Apparently these meters are not really suited
for that higher voltage tube gear, even though both the AC and the DC
ranges go to 1000 V.

I do find the 32 V limit on some of those fuses sort of an oddball
figure though. Any voltage from 32 to 100 V is not going to arc much.
Even 120 V AC line voltage really does not arc very much. Most of the
arcing I have seen has been over 250 V. The CRT anodes on old CRT tv
sets were notorious for arcing, but that was several thousand volts. I
have seen (and felt) the arcing from electric livestock fences (that
bites, and always makes me use my worst vocabulary). Those fences are
generally 2000 to 6000 volts.

Anyhow, this has been an interesting thread. I learned more about fuses,
which I have used for decades but never given much thought to them,
other than selecting one that is the right amperage and fits the holder.
It is likely I have used automotive fuses on tube gear that were not
rated for the voltage. Now I will be more aware of that.

Speaking of arcing. There is a youtube video where a main high tension
line on a tower is disconnected, and that forms am arc that keeps
growing taller. (Called a Jacobs Ladder). If I recall, the voltage is
something like 500,000 volts. The guys open 3 switches on the tower (3
phase), and that arc occurs. Those switches are probably one of more
feet of gap, but at that voltage it dont seem to matter. That's an
awesome video.....




There is a lot more to the fuses than meets the eye..

I don't know about the low voltage fuses, but wild guess for the 32
volts is most of them were used in cars and trucks where 24 volt
batteries were the highest and the 32 was some safety factor.

The 250 volt is good for common house voltages in the US.

My Fluke meter has 2 fuses in it and they are both rated for 1000 volts.
One is for 11 amps and I don't recall the lower curent one. That is so
it will meet the CAT 3 requirements. If you have not heard of the CAT
requirements, you should look it up on the internet. I don't know wht
the voltage ratings are for my old Simpson 260, but should look one day.
I do have abox of fuses that will fit in my Fluke but they are only
rated for 600 volts AC. As I don't work around anything but around the
house I would use them if one of the origional ones blow. If I was
still working and around the 480 vot 3 phase stuff that had 500 amp or
more fuses in it, I would only replace with the origional type.

I do have a hand full of the Harbor Freight 'free' voms scattered around
the house and cars. Good enough for quick checks. They are really very
accurate for the price (usually less than 1 % off the Fluke) as I
compaired them with some of the Fluke meters.

I do remember drawing arcs of several inches off the old black and white
TVs. I think they ran about 10 to 12 thousand volts.

You mentioned the Jachobs ladder. I have made them out of old neon sign
transformers and some furnace igniter transformers and some rods about 2
feet tall.

bud--
Guest

Fri Feb 02, 2018 6:25 am   



On 1/31/2018 5:50 PM, Ralph Mowery wrote:
Quote:
In article <2i647dla33h4gegvdpqbqn6k5ugu9qeein_at_4ax.com>,
oldschool_at_tubes.com says...
Fuses that have a higher voltage rating are fine to use in the low
voltage applications. They only work on the curent. In those
inexpensive meters with fuses only rated for 250 volts, they could be
dangerous at higher voltages. We were shown a trainging film by the
Fluke salesmen. They showed what could hapen if you had a low voltage
fuse and had the meter set for ohms or amps and put it across a 480 volt
line with plenty of curent. The fuse would arc over and the leads would
melt down. You would too if you were holding the leads. They make some
special fuses for them to get the higher CAT ratings.


Ok, that makes sense. Apparently the element inside the fuse must melt
for a wider gap on higher voltage rated fuses. Which would occur because
of the type of metal used and/or shape of the wire. I have seen fuses
with that element looking wavy, so I suppose that has something to do
with it. This is all mostly just a guess, but something has to make that
gap wider to prevent arc-over.

I can see arcing at voltages above 250 V. I have worked on lots of old
tube tv sets, and have seen the B+ high voltage jump across tube socket
pins and other places. Most of the time the voltages were from 300 volts
up to nearing 600 volts. Apparently these meters are not really suited
for that higher voltage tube gear, even though both the AC and the DC
ranges go to 1000 V.

I do find the 32 V limit on some of those fuses sort of an oddball
figure though. Any voltage from 32 to 100 V is not going to arc much.
Even 120 V AC line voltage really does not arc very much. Most of the
arcing I have seen has been over 250 V. The CRT anodes on old CRT tv
sets were notorious for arcing, but that was several thousand volts. I
have seen (and felt) the arcing from electric livestock fences (that
bites, and always makes me use my worst vocabulary). Those fences are
generally 2000 to 6000 volts.

Anyhow, this has been an interesting thread. I learned more about fuses,
which I have used for decades but never given much thought to them,
other than selecting one that is the right amperage and fits the holder.
It is likely I have used automotive fuses on tube gear that were not
rated for the voltage. Now I will be more aware of that.

Speaking of arcing. There is a youtube video where a main high tension
line on a tower is disconnected, and that forms am arc that keeps
growing taller. (Called a Jacobs Ladder). If I recall, the voltage is
something like 500,000 volts. The guys open 3 switches on the tower (3
phase), and that arc occurs. Those switches are probably one of more
feet of gap, but at that voltage it dont seem to matter. That's an
awesome video.....




There is a lot more to the fuses than meets the eye..

I don't know about the low voltage fuses, but wild guess for the 32
volts is most of them were used in cars and trucks where 24 volt
batteries were the highest and the 32 was some safety factor.

The 250 volt is good for common house voltages in the US.

My Fluke meter has 2 fuses in it and they are both rated for 1000 volts.
One is for 11 amps and I don't recall the lower curent one. That is so
it will meet the CAT 3 requirements. If you have not heard of the CAT
requirements, you should look it up on the internet.


The fuses are not just voltage rated. The fuses Fluke uses are rated for
interrupting on circuits with high available fault current.

The available fault current rating is very familiar to electricians
working on power circuitry, like where you used to work.

"Category rated" meters need to be used on high capacity power equipment
- you must have used them where you used to work.

Why use the right fuse, and in particular Cat rated meters:
https://www.youtube.com/watch?v=Hp1JdVwbN_U
and
https://www.youtube.com/watch?v=P35HRYHFz7c

"Arc flash" has been recognized as a danger, and provisions are creeping
into the US National Electrical Code, and it is a particular issue with
OSHA. "Personal Protective Equipment" may have to be worn when access
covers are removed, and some equipment is not safe to work on live.

The smartest electrician I have met was on a trouble call to a food
plant. He wanted to measure the motor current on a moderately large
motor. The only place to do that (and a good location) was the motor
starter. It was in a 480V motor control center - a frame with module
spaces that motor starter "buckets" were installed into. He opened the
door and put a clamp on ammeter on the motor lead, absolutely common
practice. It is not known what happened next, but there was an arc
flash. He was in the hospital for quite a while. Some of his injuries
were from copper vapor condensing on his skin. He looked younger after
the plastic surgery. Among the damage to the plant - one of the high
voltage primary fuses to the supply transformer for the building blew
and its fuseholder was damaged and had to be replaced.

It can be a problem at lower voltages too. A downtown building had a
mere 208/120V service, but high available fault current with 4 or 6
supply conduits. The service 'burned down' (no one around). Some of the
service wires burned back into the conduits, with a few welding
themselves to the conduit. (The were attached to the utility transformer
vault bus bars with "cable limiters", a combination lug and fuse - fuse
was blown.) Some of the wires burned back and remained live.

Some of you probably have exposure to high capacity power equipment,
like where you used to work.

Phil covered some of this also.


Quote:
I don't know wht
the voltage ratings are for my old Simpson 260, but should look one day.
I do have abox of fuses that will fit in my Fluke but they are only
rated for 600 volts AC. As I don't work around anything but around the
house I would use them if one of the origional ones blow. If I was
still working and around the 480 vot 3 phase stuff that had 500 amp or
more fuses in it, I would only replace with the origional type.

I do have a hand full of the Harbor Freight 'free' voms scattered around
the house and cars. Good enough for quick checks. They are really very
accurate for the price (usually less than 1 % off the Fluke) as I
compaired them with some of the Fluke meters.

I do remember drawing arcs of several inches off the old black and white
TVs. I think they ran about 10 to 12 thousand volts.

You mentioned the Jachobs ladder. I have made them out of old neon sign
transformers and some furnace igniter transformers and some rods about 2
feet tall.



Ralph Mowery
Guest

Fri Feb 02, 2018 9:15 pm   



In article <mMRcC.852$9%2.323_at_fx36.iad>, null_at_void.com says...
Quote:

My Fluke meter has 2 fuses in it and they are both rated for 1000 volts.
One is for 11 amps and I don't recall the lower curent one. That is so
it will meet the CAT 3 requirements. If you have not heard of the CAT
requirements, you should look it up on the internet.

The fuses are not just voltage rated. The fuses Fluke uses are rated for
interrupting on circuits with high available fault current.

The available fault current rating is very familiar to electricians
working on power circuitry, like where you used to work.

"Category rated" meters need to be used on high capacity power equipment
- you must have used them where you used to work.

Why use the right fuse, and in particular Cat rated meters:
https://www.youtube.com/watch?v=Hp1JdVwbN_U
and
https://www.youtube.com/watch?v=P35HRYHFz7c

"Arc flash" has been recognized as a danger, and provisions are creeping
into the US National Electrical Code, and it is a particular issue with
OSHA. "Personal Protective Equipment" may have to be worn when access
covers are removed, and some equipment is not safe to work on live.

The smartest electrician I have met was on a trouble call to a food
plant. He wanted to measure the motor current on a moderately large
motor. The only place to do that (and a good location) was the motor
starter. It was in a 480V motor control center - a frame with module
spaces that motor starter "buckets" were installed into. He opened the
door and put a clamp on ammeter on the motor lead, absolutely common
practice. It is not known what happened next, but there was an arc
flash. He was in the hospital for quite a while. Some of his injuries
were from copper vapor condensing on his skin. He looked younger after
the plastic surgery. Among the damage to the plant - one of the high
voltage primary fuses to the supply transformer for the building blew
and its fuseholder was damaged and had to be replaced.

It can be a problem at lower voltages too. A downtown building had a
mere 208/120V service, but high available fault current with 4 or 6
supply conduits. The service 'burned down' (no one around). Some of the
service wires burned back into the conduits, with a few welding
themselves to the conduit. (The were attached to the utility transformer
vault bus bars with "cable limiters", a combination lug and fuse - fuse
was blown.) Some of the wires burned back and remained live.

Some of you probably have exposure to high capacity power equipment,
like where you used to work.



Where I worked was in a very large plant. The primary feed came in from
2 directions so we would not loose power if just one of them failed.

From there it was cut to 13,200 volts and feed to other parts of the
plant where much of it ws converted to 480 volts 3 phase. We were
always working on 480 volt circuits that could have up to 500 amp fuses
feeding them. We used either Fluke meters or the good old Simpson 260
and the old analog Ampprobe . No 'hobby' or consumer grade meters in
the plant.

One fellow at work was just turning on a 480 3 phase breaker for the
motor starter in one of the motor control centers. It was only about 10
or 20 amps as I recall. Good thing the door was closed on it at the
time. There was a major melt down. It took out the buss bars behind
it. Those were rods about an inch or more in diameter. Hollow, not
solid. We had to replace the whole MCC. That was about 50 circuits
ranging from a few amps to about 50 amps in that particular MCC.

Then there were the low 24 volt circuits ar about 20 milliamps. Nothing
to get excited about. Just had to really keep in mind what we were
working on .


Guest

Fri Feb 02, 2018 11:07 pm   



On Wed, 31 Jan 2018 18:11:30 -0500, Ralph Mowery
<rmowery28146_at_earthlink.net> wrote:

Quote:

The initial item was cheaper on Ebay, and with free shipping, Thats all
I paid, and checking out was much quicker too. I dont know why anyone
even bothers with Amazon. They're crooks....





A while back I ordered some coffee off Amazon. It shipped from Target.
I looked at the Target site and it was less from them, so from then on I
go to the Target web site. Would go to Target, but it is about 30 miles
one way from here.

I live in a small town so not too much around here. Even with some
shiping charges, it is less expensive for me to order things.

Really came out a while back with Best Buy. Ordered a 60 inch TV tht
had free shipping. Two people came out and set it up. They turned it
on,but said they could not mess with the cable TV as per company policy.
They carried off the packing material and offered to carry off the old
TV. All that service was free. The nearest BB is about 30 miles away.

While I do order from Amazon, I also check other places for the best
price.


Years ago, I ordered a few books and DVD movies from Amazon. That was
before they started playing all their stupid games. Back then, I was
able to look at the item, see it's ACTUAL price and shipping, and
checkout easily without any minimum order or requirement to join their
damn "club". Back then Amazon was mostly just there to sell books and
recordings.

I am the kind of person who hates money games both online and in brick
stores. I once shopped at a Walgreens store that required membership to
their "rewards club". I only went in there to buy a cold drink (soda) on
a very hot day. The soda was on sale for something like 79cents. When I
got to the checkout I was asked for my rewards card. I told them I did
not have or want one. I was then told that this soda would cost me about
$2, without the rewards card. She handed me the sign up form. I quickly
looked it over and said "sorry, I dont give out personal information,
due to the risk of identity theft". She said, ok, but then you dont get
the sale price. I replied "and then you dont make a sale", and I walked
out of the store and have never gone back to any Walgreens store since.

I guess Amazon is now the online version of Walgreens, and from what I
understand, I would have to pay them to join their bullshit "club". NO
THANKS!

Even though I'm retired, I have a lot of things to do and even if I am
not real busy, I have projects to do, friends to visit, and personal
things that need to be accomplished. I do not have the time or the
interest in playing these money games, which waste my time. When I shop,
I make a list, grab what I need and want to exit the store as quick as I
can. While I like saving money, as do most people, I am not selling my
identity for a bag of free potato chips or to save a few pennies. If
people knew how much money those stores make off selling their mailing
lists, they would have a panic attack, when they realize all they get in
return is a couple bucks worth of savings from time to time.

I too live in a rural area, and our local town has little for shopping.
We have a dollar store (I like that place). We have 2 grocery stores
which have fair prices. We have a Shopko, that place has outrageously
high prices. And we have a local ripoff hardware store that charges 2 or
3 times what the item would sell for at most other stores. Our local
lumber yard is the same, very over priced. That's about all we have for
stores.

The nearest larger city is 55 miles away for me (each way). That's the
only place I can go to shop at electronic stores, home improvement
stores, or buy anything beyold the very limited things in our small
town. There is however a Walmart about 25 miles from here. Either way,
its costly for fuel and time consuming to go to those stores. So, if I
need some special thing, I add it to a list and try to limit my trips to
the big city to once a month. Or I go to that Walmart. Otherwise I am
stuck paying the very high local prices, or shopping online. I do a lot
of business on Ebay. At least Ebay puts the price upfront including the
shipping and I dont have to play stupid games. Ebay also does a decent
job of dealing with defective items and other problems for the most
part.

Goto page Previous  1, 2

elektroda.net NewsGroups Forum Index - Electronics Components - Need fuses for Multimeter

Ask a question - edaboard.com

Arabic version Bulgarian version Catalan version Czech version Danish version German version Greek version English version Spanish version Finnish version French version Hindi version Croatian version Indonesian version Italian version Hebrew version Japanese version Korean version Lithuanian version Latvian version Dutch version Norwegian version Polish version Portuguese version Romanian version Russian version Slovak version Slovenian version Serbian version Swedish version Tagalog version Ukrainian version Vietnamese version Chinese version Turkish version
EDAboard.com map