Hello, I'm writing this guide because I've seen alot of nice old electrical meters for sale on ebay but most of the people selling them dont know how to test them, so have no idea if the meter they're selling is working or not.

This guide will tell you how to test a few different kinds of old voltmeters (which measure voltage) and ammeters (which measure amps).

If you test your meter and the needle moves; it works! This means it will probably get more bids and sell for more! I have often been put off buying vintage electrical meters because the seller didnt know how to test them so had no way of knowing if they worked or not.

Important! : unless it says otherwise on the face of the voltmeter allways test them with DC (direct current) from a battery, testing them with AC (alternating current from mains electricity) will almost certainly burn them out and destroy thier insides.

Preliminary checks and Equipment:

• First check the needle moves, shake the meter gently and the needle should wobble then go back to its orriginal position, which is hopefully zero but many of these old meters are slightly "off". Some have zeroing knobs to fine tune where the needle is before an electric current is connected to the meter. If the needle doesnt move, it might be broken but dont give up yet we've only just begun! Also some meter's needles only move properly when they are held vertically or at an angle.

• Next check your terminals are clean [But wait, whats a terminal? Dont worry that will be explained for each meter.] Sometimes it is impossible to clean the terminals completely because the metal has corroded too much. Having unclean terminals will decrease conductivity, almost to zero if they are very dirty. You can clean them with brasso if the meter has brass terminals or if the terminals are another metal, cleaning them with a slightly damp peice of kitchen roll/strong tissue (put you back into it! give them a good hard scouring!) should do the job, make sure they are dry before you test the meter!

• Another note about terminals; if you connect the - (negative) to the + (positive) and vice versa, the needle will move backwards, this shouldn't cause any problems, just switch round your wires and it should move correctly!

• Okay Now you should be ready to go, heres what you need to test your vintage meter:

A battery- 9 Volt batterys are best unless your meter measures very low levels of voltage, than perhaps you should stick with an ordinary AA battery. Also check your batteries arent flat before you begin!

Two wires- With about 1 or 2 cm of exposed wire at each end

Crocodile clips- are optional but helpful!

Heres my testing kit:

There are many different kinds of electrical meter and each one is tested slightly differently, heres a few different kinds often seen for sale on ebay and how to test them!

Pocketwatch Voltmeters

There are some very common voltmeters, test these by connecting your battery to the short lead comeing from the top of the voltmeter and one of the terminals at the bottom.

The terminals in this case are the "plug" on the end of the lead and the "feet" or spike on the bottom of the meter.

The voltmeter to the left in the picture has two terminals on the body at the bottom and one on the lead whereas the one on the right has two on the lead and one on the bottom, either connect one bottom terminal and the lead from the top to your battery, in the case of the one on the right, or for the one on the left, connect one of the plugs from the lead to one wire from your battery and the other wire to the single terminal spike on the bottom.

Changing between the two terminals on the bottom of the left meter and the two terminals of  the lead on the right one will give you different readings, they change the level of sensitivity for use with very high or low voltages. For example; connecting the lead and terminal "B" on the left voltmeter measures between 0 and 120 volts, and terminal "A" measures between 0 and 12 volts.

The positive and negative terminals are usually marked but if they arent, the bottom feet/spikes are usualy + (positive) and the lead - (negative). Just use trial and error to find which is which if you want!

Sometimes the wire inside the lead will be broken, but I will adress this problem at the end!

"Classical" Voltmeters / Ammeters

These meters can differ greatly from one to the other but all work in a very similar way. Firstly some of the differences you may notice between these meters:

• Some measure Voltage and others Amps (or amperes its the same thing as amps only an older spelling/wording)
• The needles positioning can be quite different: some come from the top others the middle and more commonly the bottom (the meter depicted above had a needle coming from the top)
• Number of terminals: is usually 2 but the meter in the picture has 3 and I've seen many with 4 terminals! (but they're more likely to be mulitmeters) [How do I test 4 terminal meters? I dont have a 4 terminal meter yet I'll write about them once I have one]
• Metal: The majority of these are brass but some are silver metals, copper, and newer ones arent even metal they're bakelite.

Okay thats about all the differences (appart from obvious ones like difference in measurement range) Lets test it!

Oh also if you didnt guess already, the terminals are the little bits of metal sticking out on the sides of the meter (sometimes the back) Often they will have a nut or screwthread attachment to hold your wire in place.

Its best to use a 9 volt battery for these because thier measurement range is often high.

For meters with 2 terminals connect the positive and negative wires from you battery to the corresponding terminal, they should be marked on the face of the meter, but if they arent it might not matter which terminal you connect which wire to! The meter depicted gives an accurate readout of amps no matter which terminal you connect the positive or negative wires to!

For meters with 3 terminals one terminal should be marked 0 or maybe 1, you should connect the corresponding wire to this terminal (or either lead, like I said in the last paragraph sometimes it just doesnt matter which way round its connected!) then another lead to one of the other two terminals. As was the case with the pocket watch voltmeters, changing between terminals changes sensitivity and the range of the readout. On the meter depicted above one terminal reads 0 and the other two 1 and 10, so connecting the - (negative) wire to 0 and the + (positive) wire to 1 measures between 0 and 1, I get a reading of 0.4 "amperes" when I connect a partially run-down 9 volt battery.

For meters with 4 terminals I do not own one of these yet! so cant tell you exactly how it should be tested! Just try connecting each terminal to each of the other terminalswith the wires from your battery, or the terminals marked with the corresponding polarity (+ or -), and see what happens! More often than not these meters measure amps and volts! So they should sell for more than a regular volt or amp meter!

Panel meters

The defining features of these meters are that the terminals are almost allways on the back and they have a flat square front with 4 holes in the corners for mounting on a panel; usually in a car or aeroplane.

Its important to note that some measure between -30 and +30 amps, these are made for cars, unfortunatly I dont know much more about them!

To test these meters just connect the wire from your battery to the corresponding terminal on the back:

Look closely, the + (positive) terminal is marked, so no confusion with this meter!

Many of these meters measure very low levels of amps or volts (the hint that they measure low voltages/amperes is they will say milliamperes or millivolts on the face or only range from 0 to 1 or 2) so its a good idea to use the AA batteries, maybe even just one AA.

Vintage Multimeters

Multi-meters measure both volts and amps, often at different levels. I think the one above may have been used in schools or colleges and it is mounted in a wooden box. Often on the old ones there are 4 or more terminals (6 in the picture above, 3 on each side) and fequently they are screw thread type terminals. Most of the time one terminal will be marked with a polarity, connect the corresponding wire to that terminal then change between all the other terminals with your remaining wire to get different read-outs from the dial.

Unscrew the "nut" part of the terminal then screw it back down on the exposed end of one of the wires to connect it and see if it does anything!

Becareful which terminal you connect each wire to, each terminal will be for measuring different voltages or amps, for example on the meter depicted above one terminal was labeled 15 volts and the other 1.5 volts, so for measuring low voltages use the 1.5 and for higher voltages the 15 volt terminal.

Is my voltmeter really broken?

Look at the voltmeter below; It is a pocket watch voltmeter, its broken: the lead and ring have been broken off the top and the pointer from the needle has been broken off, prising open the back (which you can do with a small screwdriver) revealed alot of rust and corrosion and before I took the lense out of the front and polished it, it was black inside probably from water damage. Definately broken. But it still looks cool!

So you've tried connecting up wires and terminals, switiching the wires round incase you got the polarities mixed up, trying different batteries incase yours were flat, but that needle still doesnt move. If you're feeling ingenious and invnetive you can try this:

That picture isnt so great at showing it but here what you can try with a pocket watch style voltmeter:

• Take off the back, there'll be a small rim which you can prise the back cover off by with a small flat-headed screwdriver, dont do it too hard or you may risk accidentally jamming that screwdriver into the delicate workings inside the meter, which isnt a good thing.

• Once the cover is off on the kind of pocket watch voltmeters that have 2 plugs on the end of thier lead, you should be able to see where the leads join to the wires coming from the mechaism inside the voltmeter.
• Take off the insulation tape on them and try connecting the battery to one of them and the terminal spike on the bottom, if the voltmeter's needle moves now it means theres a break inside the lead.
• Remember to replace the tape, often it will no longer stick because the aged glue will have become dry and uselss, so you need to replace it wil electrical tape or a few layers of regular tape
• Now, for repair: You could try replacing the lead if you have some flex (that wire with the fabric on the outside, like the kind used on the voltmeter already) Soldering it directly to where the original leads were soldered, or you could leave the orriginal authentic leads on the voltmeter for decorative purposes and let the buyer of your volt meter decide what to do.

• On the other kind of pocket watch voltmeter, with two terminals on the body and one "plug" on the lead, do the same to remove the back.
• Now find where the lead conects inside, it should be held in pace by a knot or a strip of metal bent around it.
• Just after where it's held, there should be some bare wire where its soldered to a very thin and delicate wire inside, use a crocodile clip to carefully connect a wire from your battery to the exposed bit of wire from the lead or blob of solder holding the thin wire in place, dont break that tiny thin wire or you're screwed.
• Connect the other wire from your battery to one of the two terminals at the bottom (try both) and the needle should move! If it moves it means theres a break inside the lead
• Now, for repair: You could try replacing the lead if you have some flex (that wire with the fabric on the outside, like the kind used on the voltmeter already) If you are going to do this cut the voltmeter's wire outside the case, where it goes into the hole at the top, it shouldnt be broken below there. That will give you enough wire to solder your replacement wire to inside the case, be careful not to bend the remaining wire too much or it could break lower down! And dont forget to insulate everything you solder with some electrical tape!

If after all those tests it still doesnt work, your battery could be flat if you forgot to check that when I told you to!

Well, thats all the information I can give you for now! Hope it helps you buy or sell a working vintage voltmeter!

This will be updated if I get any more voltmeters unlike the ones I have written about here! Keep checking for more volt or amp meter information here!

Farewell.