This article introduces the straightforward concepts of multimeters and explains exactly how to usage them for basic measurements. Multimeters are one of the most useful electrical and also electronic aids available to us. Properly they are our eye to see electricity. The capability to use a multimeter is important if you require to know what is walk on electrically. A multimeter is, as the name suggests, a meter qualified of lot of functions. A an easy meter will enable us come measure and also test AC voltages, DC voltages, DC polarity, resistance and also often current. More advanced meters additionally measure frequency, capacitance, transistor gain, and/or inductance.

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Analog vs Digital Multimeter

Multimeters come in plenty of shapes and also sizes. However there space basically two types:

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The basic differences are outlines in the adhering to table:

Analogue metersDigital meters
1. Suggest with a reminder that moves across the face of the meter.1. Screen the measured worth in actual digits (numbers).
2. Not as precise as a specifically calibrated digital meter.2. Generally regarded as an ext accurate than analogue (only if they have actually been appropriately calibrated).
3. Deserve to require some practice to conveniently read exact voltages, although they are really useful in reflecting that a voltage is present.3. Simpler to read specific values 보다 on analog meters. However this is frequently an end kill when all you require to understand is if a voltage exist or not.
4. Particularly suited to measuring voltages that differ quickly. The pointer closely follows the voltage together it varies up or down quickly.4. Display misleading outcomes if the measure up voltage different quickly. This is due to the fact that most digital meters require a 2nd or an ext to review the measured voltage. If the voltage different greatly during this time, then the reading will be wrong.
5. Just require a battery as soon as measuring resistance.5. Call for a good battery to occupational on every settings.

If girlfriend don’t own a meter, or cannot readily borrow one, then it is time come invest in one. A basic meter will more than likely be enough for her needs. That is one that just reads AC and also DC volts, resistance and DC current. The selection between analogue and digital is yours, and will rely on access as much as her budget and preferences. The is no recommended to salary too much money because that your very first multimeter, as your usage of it may not be justified. But a meter the does the basics is really usful.

If you should purchase a multimeter, here is a attach to Amazon’s range in USA or UK orAustralia. Disclosure: If girlfriend buy through these Amazon links Geoff receive a little commission from every sale.

Digital meters space commonly easily accessible in most electronic stores. Analogue meter are regularly regarded together “old technology”. However in many cases an analogue meter may be the just meter easily accessible that is functioning (since they don’t need batteries to read voltages). Both types of meters will certainly be disputed in this chapter. If you have actually a meter, please have it v you together you check out this article. Check out the instructions because that your specific meter to be aware of the functions. Where possible use her meter to carry out the exercises as useful examples.

Measuring Voltages on your Multimeter

No issue what type of meter girlfriend have, you need to know about what type of voltage you are measuring. The an initial choice is between AC and also DC. As a guideline, common sources are:

For AC: transformers, alternators (often erroneously called generators), residence wiring, irradiate sockets, strength outlets (wall sockets).

For DC: batteries, solar panels, cars, electronic equipment.

Once you have figured out if you will certainly be measuring AC or DC, you need to choose this on your multimeter. Describe your meter instructions. Many meters will certainly not be damaged by selecting AC rather of DC, or DC rather of AC. But the meter won’t read correctly, if in ~ all.

The following step is come consider about the magnitude of the voltage you will certainly be testing. Then select on your meter a selection that is bigger 보다 that voltage.

Example 1: You want to measure up the voltage in ~ the wall outlet. It need to be 220 or 240 volts, select the 250 or 300 volts range on AC.

Example 2: You want to measure up the voltage that your auto battery. It need to be 12 volts. Select the 15, 20, 25, 30 or 50 volt selection on DC, (depending on your meter’s ranges).

If you room not sure what the voltage should be, then start on the highest range.

Analogue MeterDigital Meter
If the meter pointer only moves a tiny bit, then choose a smaller range. Proceed to select a smaller selection until the reminder is midway or higher.If the readout reads 0.01 or a comparable very low reading, select a lower range until a much more meaningful analysis is displayed.
If the tip goes off the scale (all the method over the right-hand side) then you require to quickly remove the probes, pick a greater range, then measure againIf the range selected is as well high, many meters will screen OL or -1 or comparable indicating overload or out of range.

Some (more expensive) digital meters have actually a feature called “auto-select” or “auto-ranging”. This means that the meter will immediately select the appropriate range for the voltage you are measuring. With these meters, all you require do is choose AC or DC.

WHICH PROBE WHERE?

Every meter has two probes. One black color probe and one red probe. The black color one is generally associated to the negative(-) or common terminal of the meter. The red probe is generally connected to the positive(+) terminal the the meter.

To avoid electrical shock when measuring voltage or current, always hold only the plastic insulation on the probes.DO no touch the steel pins

Measuring AC

When measure AC, the doesn’t matter which probe goes come the step (sometimes known as “active” or “hot”), and which probe goes to the neutral (sometimes well-known as the “cold”. That is, AC has actually no polarity (see the post on AC and DC for an ext details).Exercise 1: To measure up the voltage in ~ a wall surface outlet, insert one probe in one hole and the other probe in the other hole. That doesn’t issue which probe go where. Try it v your meter:

Select AC volts, 250 or 300 volts range (depending on your meter’s ranges).Being certain not come touch the metal points that the probes, placed one probe in one of the holes in the wall outlet. Placed the other probe in the other outlet hole. Her meter need to read somewhere close to what the voltage need to be (110, 220 or 240 volts).Now, quiet being sure not come touch the steel points that the probes, swap the probes over. That is, eliminate both probes indigenous the outlet holes, swap lock over and carefully re-insert them. Your meter have to read the same as that did before. This mirrors it doesn’t issue which method the probes go once measuring AC.Measuring DC

When measure DC, you have to put the red probe come the positive(+), and also the black color wire come the negative(-) the the voltage gift measured. If girlfriend mix this up and reverse the wires, climate the meter will review backwards. The is, top top analogue meters, the reminder will quickly move turn off the left-hand side of the scale. If this happens, no permanent damage normally occurs, merely reverse the method you have actually the probes. On digital meters, all that happens is that a “-” sign appears in former of the numbers indicating a negative voltage.

Exercise 2: To measure the voltage of a car battery.

Select 15, 20 or 50 volts DC on your meter.Place the red hopeful probe ~ above the battery confident terminal.Place the black negative probe on the battery negative terminal.A an excellent battery should read in between twelve and fourteen (12-14) volts.

A usual use for a multimeter is come detect which lead from a battery or power supply is positive and also which is negative. When you don’t recognize which is which, organize one probe on one of the leader to it is in tested, and then momentarily touch the various other lead through the other probe. If, on an analogue meter, the reminder moves off to the left, then swap the probes over. When the meter reads correctly, the red probe is linked to the optimistic wire (or positive battery terminal). Top top a digital meter, if the “-” sign appears, then reverse the probes because that the red lead to be connected to the positive.

Exercise 3: detect the positive end of a small flashlight battery.

Analogue MeterDigital Meter
Ensure the red probe is linked to the optimistic terminal that the meter.Ensure the red probe is linked to the hopeful terminal of the meter.
Select DC volts, and also the 3 or 10 volts range (or whatever your meter has).Select DC Volts, and the 2 volts selection (or every little thing your meter has).
Connect the black result in either end of the battery. Momentarily touch the red probe versus the other finish of the battery.Connect the black lead to either end of the battery. Touch the red probe against the other end of the battery
If the meter reads correctly, go on come the next step. If the tip moves off to the left, change the probes around. The is, affix the black probe come the end you just momentarily touched through the red probe. Now touch the an initial end through the red probe. The meter need to now read correctly.If the meter reads effectively (i.e. No “-” sign), go on come the following step, if a “-” sign appears, readjust the probes around. That is, attach the black probe come the end you simply touched through the red probe. Now touch the very first end with the red probe. The meter should now check out correctly
The end linked to the black color probe is the negative(-) wire. The other end is positive(+).The end linked to the black probe is the negative(-) wire. The other finish is positive(+).

 Practical points come Note

1) The meter reads the voltage in between the two probes, no necessarily the full voltage in the circuit. This may seem like a reasonable statement, yet many human being have been trapped by not expertise the difference.

2) Looking at the calculation voltage that a HiFi amplifier is best done with an analog meter.

Exercise 4: that doesn’t matter if you usage the left or best channel, but you need to use the positive and negative terminal that the one channel.

Select AC and also the 50 volt range on her meter.Connect one probe to the negative speaker terminal.Connect the other probe to the confident speaker terminal.The meter pointer have to dance up and also down with time with the music. How far the needle moves will rely on the volume control.

This is not a an extremely practical means of measure the output, however it does provide an amazing display. To appropriately measure the output capabilities of her HiFi amplifier you need other check equipment.

Measuring Resistance on her Multimeter

A valuable feature of multimeters is their capacity to measure up the resistance in a circuit. Back the exact resistance in a circuit may not be helpful to you, regularly knowing the loved one resistance is. Example: understanding the precise resistance that your clothes iron isn’t important. But knowing the there is part resistance (that the the heating element) tells you the it must work. No resistance indicates a damaged connection which demands to be fixed.

The best method known to damage your meter is to shot to measure up high voltage (like 220 volts AC) while tho on the resistance range.Always certain the strength is rotate off and disconnected before measuring resistance

The an approach of setup your multimeter for measuring resistance is various for analogue and also digital meters. Therefore, we will look at each separately.

 Analogue Multimeter Digital Multimeter
1. Choose resistance. This is regularly signified by the Ohms prize “Ω”.1. Select Resistance. This is regularly signified by the kilo-Ohms price kΩ.
2. Calibrate the meter. To perform this situate the “Ohm’s Adjust” knob, a small control favor a volume control. Organize the metal points the the black and also red probes together so the they touch each other. If they room still touching, move the “Ohm’s Adjust” regulate until the needle aligns v the much right-hand side of the scale. This should be “0” top top the ohms scale (normally the height scale).2. Digital meters space pre-calibrated so no additional calibration is required
3. Place the probes across the resistance to it is in measured. For most resistance dimensions it doesn’t issue which probe goes where – that is, that is no polarity conscious3. Ar the probes across the resistance to be measured. For many resistance measurements it doesn’t issue which probe goes wherein – the is, it is no polarity conscious
4. Check out the variety of ohms from the meter. The optimal scale typically is the range to review for resistance. Assume the needle is pointing in ~ “15”. If the variety was Ω x 1, climate you space measuring 15Ω. If the variety is Ω x 10 climate you space measuring 150Ω. An in similar way Ω x 100 = 1500Ω and also Ω x 1K = 15,000Ω or 15kΩ. If the needle is close come the left-hand side of the scale, choose the following range.Example: the variety is ~ above Ω x 1. The needle is pointing at 1200. Readjust the range to Ω x 10 for the needle to point at 120.4. Read the number of ohms native the meter. The numbers displayed indicate the resistance in Ohms. Digital meters normally measure in Kilo-ohms (KΩ). Because of this if the meter is mirroring 1.5, it way 1.5KΩ, or 1,500Ω, no 1.5Ω. Take note of the little symbols denote the variety (if displayed). This is especially important top top “auto-ranging” meters. There is no noting that it is Ω, KΩ or MΩ girlfriend can easily be mis-led right into a false reading
5. If the resistance in the circuit gift tested is an extremely high, or no circuit at at all, climate the needle won’t move. That is, the needle remains on the left-hand side of the scale, reflecting infinitive(∞) ohms5. If the resistance in the circuit gift tested is an extremely high, or no circuit at all, climate the meter will try and phone call you. There space various methods to suggest this condition. Some display screen OL, definition “Open Loop” or “Over Load”. This method the resistance is for this reason high the is taken into consideration to be no circuit in ~ all, or at least outside the range of measurement. Some meters flash 1.999 to suggest this condition.Check to watch what your meter does v both leads unconnected.

Some common terms

Short Circuit: as soon as there is zero resistance in the circuit, the is stated to be a “short” circuit. This is shown on all meters by reading “0” (zero ohms) – or close to zero ohms.

Open Circuit: when there is so lot resistance the the meter can’t it is registered it, that is said to it is in “open” circuit. This usually indicates that over there is no connection between the probes.

Note: when there is an open circuit, the meter have the right to sometimes imply some resistance (often measure up in Mega-ohms). This is normally caused by touching the probes with your hands, and also the meter is in reality measuring her skin resistance.

Practical uses of measure Resistance

As discussed earlier, understanding the precise resistance in a circuit is frequently not as crucial as understanding if there is a circuit at all, if there is a quick circuit, or if over there is an open circuit. Shot the complying with exercises as examples.

Exercise 5: check a bring about see if it is faulty or not. This can be a lead from your HiFi, a power expansion lead or a microphone lead.

Select Resistance and also the Ω x 1 scale. If utilizing an analog meter, calibrate the to check out 0Ω when shorting the probes together.Check the command for quick circuits. Using only one finish of the lead, place a probe on every connection. Your meter must read prototype resistance, saying there is no circuit between the two probes. If her meter shows close 0Ω, (a short circuit), then it requirements to be addressed or replaced. The most common places for “shorts” to show up are in the plugs at either end.Check the lead for continuity. Making use of both ends of the lead, location one probe ~ above the same suggest at each end. Her meter should present a brief circuit (0Ω). Currently do the same for the other connection on every end. If on either link you perform not acquire a quick circuit, climate there is no a consistent circuit in the lead whereby there must be. It probably way the lead is broken. The normal means to fix this is to reduced 10cms off either end of the lead, check that the lead now has continuity, and then rejoin the connecters. This is recommended since the greatest wear ~ above the lead is wherein it bends at the exit of the plugs. If after replacing the end there tho is no continuity climate it is probably ideal to replace the lead.

Note: some stubborn leads will certainly only show an open up circuit after ~ bending the lead severely at either end. This says the command is broken but quiet making intermittent connection. It also should be cut much shorter and re-joined.

Exercise 6: check a light bulb to check out if it is OK. If a flashlight doesn’t work-related it is an excellent to understand if the batteries space flat, if there is a poor connection or the bulb is blown.

Select resistance and the Ω x1 range. If utilizing an analog meter, calibrate it to read 0Ω once shorting the probes together.Place a probe ~ above each link on the light bulb. Your meter should display a circuit. Frequently it shows the resistance is virtually zero ohms, this is normal and also suggests a an excellent light bulb.

Note: the resistance that a light bulb increases considerably when strength is applied. This is because, just like most resistances, the resistance increases with temperature.

If the light bulb checks the end OK, choose DC volts on her meter and also check that the battery are additionally OK.

Exercise 7: examine if a fuse is blown or not. If girlfriend think a fuse is blown, the best means to understand for certain is to remove the fuse (with the power off!) and test it v your multimeter.

Select resistance and also the Ω x1 range. If utilizing an analog meter, calibrate that to review 0Ω when shorting the probes together.Place a probe top top each finish of the fuse. Your meter should display a brief circuit (no or very low resistance). If over there is really high or infinitive resistance, then the fuse is blown.

Measuring current on your Multimeter

Most multimeters have actually the basic to measure tiny amounts that DC current. Some meters also allow the measure up of AC current. Return the measure of DC present is defined here, the procedure for AC present follows similar principles.

When we measure voltage, we are measuring the distinction in voltage native one probe come the other. That is, we measure the voltage throughout a certain resistance.

Example: here we have actually two 1.5 volt

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batteries linked in series to provide 3 volts across the resistance (a irradiate bulb). By place the probes as shown we deserve to measure the voltage (3 volts) throughout the irradiate bulb.

To measure the existing in a circuit we have to measure the present flowing v the resistance. We have seen that we can’t simply location the probes throughout the resistance, as this gives us the voltage no the current. For this reason what is the secret?

In the write-up on The Dreaded Ohms Law, we learned that the present flowing with a collection circuit is the exact same throughout the whole of the circuit. Thus if we deserve to measure the existing flowing with any part of the circuit, us are effectively measuring the current flowing v the resistance. That is, the present flowing through the resistance is the same as the existing flowing v the wire, i beg your pardon is the exact same as that flowing with the batteries (to usage our example).

So exactly how do we perform all this? We might cut the wire in between the battery and the irradiate bulb.

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Then affix one probe to every of the reduced ends, v the multimeter selected to measure up DC current. This would work-related as we room measuring the existing flowing v the cable (and the multimeter). Since it is a series circuit, we are also measuring the existing flowing with the irradiate bulb and the batteries.

However it is not always wise to cut wires unnecessarily. In ours example, an apparent place to rest the circuit and also insert ours probes would certainly be in ~ the finish of among the batteries. Many battery holders have actually a feather to assist make a great contact. That is normally feasible to separate the batteries and also insert a small piece that cardboard to isolate the battery from each other. Then it is a matter of just placing a probe on either side of the cardboard.

Whichever method it is possible to rest the circuit, it is in ~ that allude that the probes must be inserted.

Which probe where?

When measure AC current, that doesn’t issue which method the red and black probes go. ~ above DC that does matter. The black color (negative) probe need to go on the confident side of the break. That is, it have to go top top the side of the “break” the is closest come the hopeful of the power supply (or batteries). If girlfriend mix this up and also reverse the wires, then the meter will check out backwards. The is, ~ above analog meters, the pointer will conveniently move turn off the left-hand next of the scale. If this happens, no permanent damages normally occurs, just reverse the way you have the probes. On digital meters, all the happens is that a “-” sign shows up in former of the numbers indicating a an unfavorable current, however the value is correct.

Practical Points to note

1. Once measuring AC present (if your meter has actually that selection), be very careful no to touch the steel points that the probes.This is since most frequently when measure up AC, that is at dangerous (high) voltages.

2. Beware of her meter’s limitations. Plenty of meters only enable the measure of very tiny DC currents. Regularly 25 milli-amps(mA) is the maximum. Many meters likewise have the volume to measure up 10 Amps. To do this you normally need to move the red probe come a various socket on the meter. This is regularly 10 amps AC only, not DC. Be sure to review the manual closely to recognize what girlfriend meter can and can not do.

3. Countless digital meters allow a best of 200mA. If this limit is exceeded, a fuse in the meter will probably need replacing. That is way to have actually a an excellent stock of replacement fuses on hand.

4. Inserting the probes between two battery is an easy way of checking the charging current being delivered to Ni-Cad batteries.

SUMMARY

To avoid electric shock once measuring voltage or current, always hold just the plastic insulation top top the probes.DO no touch the steel pins

When measuring AC, the doesn’t issue which way the probes go.

When measure up DC voltages, the red positive probe goes to the hopeful side of everything is gift tested.

When measure resistance, ensure there is no power applied to the resistance gift tested. It doesn’t issue which means the probes go.

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When measure current, the is necessary to break the circuit in an suitable place and insert the probes in collection with the circuit under test. The black probe goes come the confident side the the break.

So there you go, take a multimeter and start “looking” at electrical energy – but do the carefully!