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Electrical instruments

Postby DIYvirgin1975 » Wed Jun 18, 2008 7:09 am

Can you please tell me what the following instruments are used for:-

ohm meter
multi meter and
neon screw driver
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Postby kbrownie » Wed Jun 18, 2008 11:51 am

Used for following measurements
ohm meter=insulation resistance, continuity,polarirty
multi meter=a few things, resistance,continuity being common
neon screw driver=not recomended for electrical measurements
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Postby chris_on_tour2002 » Wed Jun 18, 2008 12:38 pm

ameter measures amps in a circuit
voltmeter measures volts
ohm meter measures resistance
multi meter does all the above plus function for detecting continuity
neon screwdriver tests to see if a circuit is live, not always reliable not recommended - use a meter instead.

if you don't know what the above equipment is for or how it is used then i'd advise that you leave well alone. electrical work is dangerous - if you are about to carry out any electrical work and don't know what you are doing then get in a pro.
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Postby ericmark » Wed Jun 18, 2008 7:05 pm

The ammeter is used to measure current. To connect it normally requires the wire the to item being checked to be diverted through the meter. Often a current transformer is used and the meter itself is a voltmeter. There are clip on varieties where only a temporary connection is required. Electrician use the clip on both to check the current being used is within the limits for the circuit and to see if something remote is working.
The voltmeter of course measures volts and is used to measure volt drop. It helps in identifying faults.
The Ohm meter is split into three types the non special is used to check bulbs etc to see if they are OK. But there is a special low ohm meter that must draw 200ma during its test and is used to check earths. The versions built into appliances testers can sometimes test with as much as 25 amp and they are used to test earth wires. The High ohm meter will use 500 volts to test and is used to test insulation again in appliances testers there is also sometime an ohm meter able to test at 2500 volt but these are reserved for when re-building class 2 equipment and are not often used.
The multi meter is as the name suggests an combination of meters and vary in design many being made for special jobs like the ones made for the motor trade.
The neon screw driver as such is not recommended but there are other similar testers which can test if power exists and can work on such low currents that they can use the human body as an aerial measuring with very low currents does however result in incorrect readings and some skill is required to interpret the results. As a result they do not help the DIY person.
One item you have missed is the prover unit. When we want to ensure any item is not live we need to ensure the tester is working and there is a box which produces 230 volt so the tester can be tested.
Many of the meters sold in DIY outlets are really designed for extra low voltage work and often the leads are not good enough for mains work. In fact a set of leads to GS38 which is the standard required for mains work can cost more than you buy whole meter for at a DIY shop.
Having seen a series of your posts and I think it is time you bought some books and learnt the basics. The internet of course can help and even using the bit size series on the BBC web page will help.
Remember a little knowledge is dangerous.

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