Testing Electric Equipments with Multimeters-A Complete Guide

Beside its important electricity parameters multimeters can also help you to find issue with electric equipments like capacitors, circuit breakers , relays, fuses and many more. Obviously you,ll need some trainings and safety guidance before doing these things but here we,ll guide you for some basic check ups. By learning some basics of multimeter you can easily check if home supply outlet fuse is working or blown out by sudden spike in voltage? And you really don,t needs to be electrician or engineer to learn these basic faults.

Tools needed for this are a digital/analog multimeter, quality test leads and safety gloves. As you know electric circuits work on a specific path, just like the roads where we travel for our destinations from one path to another. When a flowing charge in a circuit find a hurdle or path break, it will result in supply breakdown or shutdown of device in other words.

We,ll explain it by simple steps that how you can check fuses, cct. Breakers , capacitors and some other necessary equipments.

How to test a Fuse with a Multimeter

Before common use of circuit breakers fuses were the only source to save circuit from surges and overloads, even today in cars and older buildings we have fuse protected supplies. Fuse is basically a piece of wire which is constructed by alloying more then one metal. It,s basic purpose is to melt earlier and break supply in case of spikes, surges and overloads. They build fuses with such material which has melting point lesser then copper or silver wires so it can cutt off supply to protect circuits.

To test a fuse follow these steps,

  1. First of all turn on multimeter and set it to continuity checking range. Also put test leads to relative sockets.
  2. Now take of fuse from where it,s installed to make sure no interuption while testing.
  3. After adjusting multimeter,s setting you can test fuse by connecting probes on opposite points of fuse.
  4. Carefully listen to meter, it should give beep sound to ensure that fuse is in good condition.
  5. You may aslo check a fuse by ohms readings, for this set its range to resistance parameter.
  6. If meter produced no sound during test or you got OL reading in ohms range that means fuse has blown out and needs replacement.

How to test a Car Fuse with Multimeters

Car fuses are bit different from general fuse we get in our home outletes or even at some industrial applications. Mostly unlike general fuses you can,t bring it out from its installation point in engine or car dashboards even under seats, so you have to test it as it is. Some blade shaped fuses could be de attach easily through a nose plier from their box for further analysis.

Suppose you are at some remote location far outside your town and suddenly car headlights goes out of order or car ac went out of power. In this scenario a digital automative multimeter can help you in finding possible fuse faults. Follow the steps mentioned below to check car fuse by yourself.

  1. First of all identify your car fuse location, mostly you,ll find it somewhere around dashboard. Or you may reach it through finding fuse box location by manual.
  2. Now turn on your multimeter and set it to dc volts, as you have to check dc voltage passage through fuse.
  3. For this purpose connect black or common probe of multimeter to negative terminal of battery. You may also connect it to some metal part near it.
  4. Now tell one of you companion to turn on engine, that,s important because this will allow all fuses to go into working condition.
  5. After this connect positve or red probe of multimeter to one point of fuse and see readings on lcd. Repeat it by connecting probe to other fuse point and note results.
  6. If it,s giving 12v reading on both points that means fuse is in working condition. On other hand if you get 12v on one point and 0 on another that will clearly indicate that fuse has blown out or malfunctioning.

How to test a Capacitor with a Multimeter

There are several methods to test health of a capacitor and it can be done through analog meter and digital multimeter. We,ll discuss all methods by steps given below.

By Digital Multimeter

  1. First of all take an accurate multimeter and set it to ohms range minimum at 1000 kilo ohm.
  2. Now disconnect that capacitor from its circuit and make sure that it has been discharged well.
  3. Then connect multimeter probes respectively to capacitor negative and positive points.
  4. If capacitor is fine the meter will give some reading initially and then turns to over limit or OL. Which means that capacitor is ok.
  5. If there,s no change in reading then probably capacitor you,re checking is in dead state.

Through Analog Multimeter

Testing a capacitor by analog multimeter is much same as by digital ones except its results observation method. Same as in dmm set multimeter range to ohms and connect its probe to capacitor points. Now keenly observe the needle movements by which we,ll asses about capacitor,s condition. If in start needle remains at low ohms value and grdually moves to infinite ohm value then the capacitor is in perfect state.

A damaged or open capacitor will not show any movement on meter,s screen. A short or burnt capacitor will give a minor ohm reading. It,s an old and perfect method to check capacitance condition.

Testing Capacitor by Capacitance meter( Dmm feature)

  1. Some of latest digital multimeters come with capacitance finding feature, we recommend you to buy a dmm with capacitance feature if you have to test capacitors frequently.
  2. Same as before remove capacitor first from the circuit where it was installed.
  3. Capacitor should be fully discharged for a more trustworthy results.
  4. Now set multimeter range on capacitance function.
  5. Check whether the probes are in right socket for capacitance test.
  6. Now connect multimeter,s leads to capacitor terminals, black with negative and red one with positive terminal.
  7. Check reading on screen, it should be equal or near to capacitor,s actual value. Suppose if capacitor is 40 uf then it should be somewhere 37 , 38.
  8. If you get reading far below the capacitor rating or no value at all that means capacitor is weakened or dead and has to be replaced.

How to test a Circuit breaker with a Multimeter

Circuit breaker is a type of electrical switch, they provides safety to appliances and circuits from short circuits, spikes and overload currents. You can say it a modern form of fuse in terms of safety but they are not like fuse which are for one time use only. Once the fuse has burnt you can,t use it again. But it case of breakers they can be used multiple times by a simple reset. To ensure their smooth operation suspected cct. Breakers should be checked timely. Kindly follow steps below to test a cicuit breaker with a multimeter.

  1. First of all make sure to do all safety steps properly, like wearing a shoe, insulation gloves and there is no water presence around electric panel where breaker is installed.
  2. Multimeter for this purpose should have safety ratings according to requirements like CAT 2 or CAT 3.
  3. Now turn on meter and set it to relative AC voltage range, suppose if we are testing a 220v system range should be set to 400v.
  4. Turn off all lights and loads running through that cicuit breaker.
  5. Connect red prong of multimeter with one of cct. Breaker point and black or neutral prong with ground screw along metal bar in panel.
  6. It should give reading around 200 to 230 volts according to voltage level.
  7. Now repeat it with other point of cct. Breaker and see results, the lower point of breaker should give valid voltage reading when breaker is at on state.
  8. Now turn of breaker and check results by connecting probe to lower screw point, it shoud give no reading at off state.
  9. If at on state you get no voltage reading then it,s time to replace that circuit breaker.

How to test Relays with a Multimeter

Relays are a type of electrical switches which are used to control devices or machineries through power logic. Usually they are consist of two contacts, normally open and normally closed. We can control them through control commands given by plc or other automation systems by energize deenergizing method. If you found an issue with relay or it,s malfunctioning it could be checked easily with help of a digital multimeter.

Follow these steps to test a relay with multimeter,

  1. Firstly locate the suspected relay and bring it out by disconnecting it from circuit or device.
  2. Generally a relay has five points, two for supply either 12vdc or 220vac. In other three points one is common, one is NC and other is NO.
  3. Now turn on your multimeter, set it on ohms range.
  4. Connect multimeter to relay coil points, it should give 50 to 130 ohm for surety that electromagnetic coils are ok. If you get an out of range readings then it,s time to replace that relay.
  5. Then letting meter to ohms setting connect multimeter probes to normally open points, it should give overlimit or OL reading.
  6. Now check normally close points and if the results are zero or close to zero then relay is absolutely fine at de energized position.
  7. Now is the time to energize relay from its power source and test it again.
  8. In energized state NO points should give a reading zero or near to it, NC points should have OL results to validate that relay is functioning properly.

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