How to use your trashy meter without blowing it up (much)

how to use your trashy meter there's a lot of snobbery in electronics about what meters are good and what meters are bad never is going oh fluke it's got to be fluke if you're starting off in electronics i actually recommend getting yourself one of these little dinky meters they're only about five pounds five dollars whatever garber free i believe just gives them away free as a gimmick very cheap uh in reality they're a perfect meter for getting used to in the first place because it means if you have a terrible instant and you do somehow connect the mains across it while it's set to resistance and it blows the metered pieces replacing the whole meter will cost less than replacing the fuse in your fluke the flux are good though for if you're doing industrial electronics or poke around in mains wiring in your home you don't want to use these meters that's when you want to use something more up markets like a fluke or one of the many other brands are made to the same standard so let's take a look at these meters i'm going to show you how they work first and then i'm going to show you how to use the ranges because i can remember buying my first meter from tandy and it wasn't it was an analog meter and it had little holes for all the different probe settings and i didn't have a clue when i was young i managed to blow up very very quickly it just stopped working went all wonky but then now i know uh what that probably was but not to worry so these meters are very simple inside they just have one calibration pot don't touch that uh they have a chip in this case it's a blob cover covered with a blob of resin covering the chip and then little uh stacks of resistors to set ranges and on the back of it there's a rotary knob that just wipes contacts around and as it wipes from round it does a couple of things that selects different resistors and it also chooses the position of that the decimal point in the display it moves according to the range as it's set things worthy of note in here there's a little fuse that fuse in this case is a 250 milliamp quick profuse f250 milliamp it's a 20 millimeter fuse if you get one of these meters it's worth getting a pack of fuses they're very cheap uh just a little glass fuse is fine for these ones uh for because you'll be using it with low voltage uh otherwise if you accidentally blow it and it's very very easy to do particularly in these meters because there's a bit of a weakness but it's also a useful feature as well i'll show you that afterwards but if you blow it it's just easy to change it there's also on the 10 amp range the high current range there is this big wire link that you should know about between the 10 amp connector and the common connector if you accidentally leave the meter in that range and then you stick it across a power supply or a battery you'll basically you'll be shorting it out through this wire link these things are super accurate for for their cost they're actually very good um the accuracy is achieved purely through using precise values of resistors and this a tiny bit of calibration this big shunt here for measuring high current all they've done is they've put a shunt in of a known size and then they fine-tuned it by just crimping it with their what looks like a pair of side cutters just crimped a little bit regularly until they've narrowed it down to get a precise value of resistance actually then gets the desired result um very simple inside very cheap they're good so let me show you what actually happens when you use these then i'll show you actually how to use it so that little chip let's zoom down this just a little tiny bit little chip just measures a very low voltage everything it doesn't matter if you're measuring resistance or you're measuring current or you're measuring the diode it's always just looking to measure as a voltage and to select a different ranges all it's doing is it's moving along resistor taps to actually change the ratio of the test leads versus what's actually going into this and the meter can also measure the ac and the dc voltage you can measure the different polarities so for the voltage it's very simple it's just a resistive divider usually for ohms it uses a known current passing through whatever resistor you connect say for instance this 10k resistor it plus is a known current and then the probes actually measure the voltage across it and by calculating based on the known current and the voltage it can work out the value of the resistor so that's it's just measuring the voltage across the resistor again if you have an unknown current in the current range it uses known resistances and it depends the range you select which resistance it is it simply determines that current by measuring the voltage across the known resistance uh and again it's the voltage goes to digital display and it knows it can actually display what the current is the diode test such a useful thing i have to say you'll find that uh 99 of your use of this meter is probably the 20 volt range and the diode and continuity test i use those ones all the time it's like almost never deviate from using those it's kind of rare to use other ranges but what you have with the diode test it uses a known voltage three volts passing through a resistor so it passes one current between the the leads at one milliamp of current and then when you actually place it across things for continuity if it detects it's below about point one volt like almost a dead short circuit it'll beep but it also displays the voltage so if you place these probes across a diode it will show the forward valve the forward voltage that diode which is a very good way of testing these it's a way of testing if a diode's working what type of diode it is and if there's a short circuit that is it there's really it's a very simple system it uses it's all just measuring voltages right let's do some tests i'm going to zoom back out here a bit do i need to zoom back out no i shall not zoom back out i shall stay where we are let's start with voltage so as i said earlier the range i use almost exclusively is 20 volts dc if you're measuring say if you're measuring above 24 20 volts say 24 volts you're going to have to move up to the range higher you want the range that's just slightly higher than the voltage you're measuring so in this case i'll put it 20 volts i shall bring in a dc supply that is approximately 12 volts we'll clip that on and i shall energize the supply and it displays 11.9 volts now if i chose a higher range it would still display the 12 volts but it's displaying a lower resolution a lower number of digits and if i go up to the highest range which is 500 volts it will just display it's not accurate even accurate that range but it will display the that uh it will display 12 volts well it is accurate enough but there won't be any decimal places so by using the lower voltage the one that's closest you're going to get the greatest accuracy 11.99 here if you go to a too low range say for this 2 volt the 2 000 millivolt range it will just display a one that means it's out of range it can't measure that it's not going to damage the meter but it just can't measure it it's important to note that there are there's a dc voltage range and there's an ac voltage range if i disconnect this i recommend disconnecting the leads before changing to other ranges if i select it to 200 volts ac but then i apply dc instead it's going to be all over the place it's going to display 25 volts that 12 volts if you ever get weird results like that make sure you're in the correct voltage dc or ac because the same that thing happens in the other direction and the reason for that is because when it's measuring ac voltage it's a very crude circuit that's just averaging the positive and the negative cycles uh at 50 or 60 hertz it's not it's just creating a very rough value it's in these meters they're not super accurate in that way good enough for 50 60 hertz uh but not not as good as a professional meter for specialist applications certainly with the high frequency power supplies you can't use the ac range because uh it will it just it will skew it completely because it will be too high of frequency for it right let's bring initiations firmer this doesn't look like a transformer it looks like a fluorescent lamp ballast but that's because it was made by a fluorescent ballast manufacturer it's a slimline transformer 240 volt in 12 volt out let me plug this in at this point i should say that you shouldn't really use these meters you can use them on 240 volts but they don't have the correct electrical safety ratings for that if i stick it in that's set to 500 volts ac it will display the 240 volt supply i've got here but it's not i wouldn't recommend it because uh you're relying on the protection of the circuit it's not so bad i've got a three amp fuse in this one but if you're probing around the distribution board and you've got things wrong particularly if you've got the current range and you stuff these leads in it could make the the whole meter explode that happens however let's go back to the 200 volt range i've got my 12 volt output here and there it is it's measuring the ac output 12.8 volts because it's not loaded down however watch what happens when i turn this accidentally to dc voltage 20 volt range and you'd think that would still read something even in the ac it doesn't the reason it doesn't it go it pretty much displays zero the reason for that is because it's averaging out the voltage uh inside and because the meter is actually going the transformer is putting out positive 12 volt and then negative 12 volts it's continually swapping polarity the average is zero that's why you get that zero if you choose the wrong range i shall unplug this now slide out the way even for batteries like say this 1.5 volt battery the 20 volt dc range is good because uh it's still accurate enough that you you could go down to the 2000 millivolt range but it's a bit harder to read because it removes the decimal point you have to work out that that's 1.3 volts but if you set at the 20 volt range it's still accurate enough it's going to give you two decimal places 1.3 volt for that battery also note the plarted the little negative will appear if i connect the positive lead to the negative terminal it will still display the voltage but it will display as a negative voltage that just indicates that the the positive lead the red lead is more negative than the black lead at this point i should i should have done this earlier in fact uh the lead positions here this is where you've got a bit of a weakness in this meter if you look at the fluke let me grab the flick again the fluke has the common the black lead this one is also marked common here the black lead always goes into the common most of these meters then you've got the other ranges you've got the volt ohm and diode in this case you've got volt ohm diode and milliamp then you get 10 amp and 300 milliamp you've got the current ranges the reason they normally keep the current ranges separate is because when you actually put them into the current ranges it by the way it measures the current it puts a very low value resistor or a dead short across it if i was to probe across the 5 amp connection this or 10 amp depending on the type of meter you'd just measure you'd see the shunt it's really important to remember to make sure the lead's in the right place in almost all instances you will have it in the the black in the common and the red and the volt oh milliamp if you put into the five amp one you will uh or the 10 amp one you're going to basically you're not going to get readings but you're going to short circuit everything you put this across it's worth knowing that what's the next range resistance when you're measuring resistance you have a series of ranges again 200 ohm 2000 ohm 20k 200k and 2000k but nice if they said two meg on there because that'd be more easier to deal with i'll just put this lead out the way here so say for instance we've got a 10k resistor brown black orange brown black and three one zero and three which is one zero and three zeros so ten thousand ohms the closest range to that that's a usable is about twenty thousand ohms when you're testing resistors it doesn't matter which way around the leads go make sure you don't hold both leads on like this because if particularly with higher value resistors your just your hands holding it can potentially skew the result that uh reading so if i then hold this on either side it will say 10.15 or thereabouts that's the 10 000 ohms and if i set it to say a higher one it would still measure it but it would be to lower accuracy so you kind of want the lowest setting possible if you go too low this is in the 2000 ohm setting uh it's not going to read it because it's out of its range and it will just display the one again some meters display ol a bit of controversy there some people say it means overload or whatever but it's not actually really overloading them here is a 100k resistor just for reference purposes let's put up the 200k range again and stick this meter across it and it's displaying 98.5 approximately there's always going to be a slight extra resistance in the leads or the contact point if i grip it with my fingers and hold it you'll see the reading goes way off because i'm actually some of the currents actually flowing me through me and that's skewing the reading next range current okay say for instance you have an led let's bring the power supply back in again i shall power this this is a bonus thing of this meter that i quite find quite useful here's the led and a resistor in series very pretty uh one of the nice features about these meters is that you don't have to change the leads into different positions when you're measuring the current however that's also a bit of a curse because if you accidentally turn around to that even with the probe in the normal place if you set it to the current uh it's basically going to put a resistor quite a low value resistor across the uh the leads and if you're probing about batteries or power supplies it can actually damage the resistors or blow the fuse in the meter that's why i say you should get more make sure you get fuses i've set it to the dc current range there is no ac current range in this meter i've set it to the 20 milliamp range because that is a known area if in doubt uh set it to the higher current range well let's start off let's set it in the 200 milliamp range if you go higher if you go to the 5 amp range you will have to change the lead over to that dedicated high current shunting side but uh i don't really make sure what if you do that switch it back afterwards just it solves problems you'll find this out possibly the hard way you may blow up your meter don't worry about it if you do so this uh i want to measure the current through this led so you break the circuit you actually put the meter in series with your circuit now the led is lit the current's flowing through the meter and it's showing 13.7 milliamps i can actually switch up to the 20 milliamp range it'll give me a bit more actually 13.62 milliamps with that it's worth mentioning that if because this puts a resistor in series to actually measure the voltage across the resistor when it's measuring current you have to be careful with where any resistance in the circuit is going to affect the current flow significantly that's particularly important with things like lots of leds and very low value resistors a limited current as soon as you add the meter in it can actually show a lower reading because the meter itself has added to the circuit resistance there is a way around that you can actually measure in circuit without interrupting it if you know the value of that resistor you can measure the voltage cross and that will ah you can then multiply i equals voltage divided by resistance and voltage measure divided by resistance that will show you the current flowing through the circuit but that's only for it's not so critical in this application next and the last range one of the most useful it's the one that my meter spends the other half of its time in is the diode and continuity test there is uh i'm going to mention dave jones here dave jones says if it's got a gain test on it it's a meter basically speaking i tend to yeah i i the only time i've ever stuck a transistor in this gain tester is just to see if it worked i never use that do you guys use the gain test i've never done it anyway the diode and continuity test is very useful you get meters that have discontinuity but they don't uh have the beeper this one has the beeper and this is where me and dave disagree now this beeper has the decisive if you touch leads like that or scratch them it has to be a certain time before it beeps and then it does so decisively my preferred meter here with this big big display it is more instantaneous and it's scratchy this is what dave calls a scratchy tester because it beeps instantly and if there's any bad connection it hisses and crackles and scratches right i prefer that because it's faster and also it shows even to get a good connection it's still crackling buzzing it means that there's actually a bad connection it can give you a little bit more information but it doesn't sound as slick and dave's going for the slickness as he does then that's just his preference uh it's fine you know this decisive it does sound better without that scratchiness i just find this uh slightly less useful than uh that so continuity the beeper is important because it means if you get a circuit board let me grab a circuit board let me grab this high voltage power supply if you're proving about doing continuity sometimes if you have to keep taking your eyes off what you're looking at to actually look at the display then you can lose track of where you were in the circuit board that's why the beeper is quite handy because you can probe about and you can follow circuitry along and just find your way about it without actually having to look up at the meter the beeper will only go if it detects a fairly decisive uh short circuit i'm not sure if it would even work with this resistor it will display a random value for the resistor actually displays a close value to the resistor rating now here is one of the most useful functions the diode setting actually passes a three volt supply at limited current uh which means that for testing leds you can actually just without necessarily relying on getting a display it will make an led light up that is very very useful the meter itself will only probably display about two volts but it puts out three volts some meters don't do that they can't test leds i prefer the ones that contest leds that's a win for this one but watch this this is a standard silicon diode it's measuring the voltage dropped across the leads uh if i put it the wrong way around so no current flows through you'll get nothing if i put it the other way around you'll see the forward voltage drop of the semiconductor junction which is about 0.6 volts 592 millivolts and from that you can actually determine if this is a schottky diode if it was about point if it was say it displayed 200 volts at 200 millivolts 0.2 volts that would be a short k this one is a a silicon at about 0.6 and that also lets you test these diodes if if both ways round showed open circuit the diode would possibly open circuit if both ways round showed just continuity beeping both ways round it would mean the diode had gone short circuit and that is about it this one also has a little tone output i think i've never really used that but as i say on this meter here i tend to use diode and continuity and the 20 volt dc range are the two ranges that this meter spends most of its time on and of those because i'm always tracing circuit boards out it's almost always in the continuity test so i do recommend getting one of the peeper this uh meter incidentally came from uh cpc in the uk it only cost about five pounds i'm going to show you a feature that makes it slightly better than this one with that dangerous shunt across the high current range let's pop this open it also comes with a cute little rubber holster which gives a sort of cheap fluke-like appeal without actually the cost of a fluke i do use fluke at work i recommend if you're probably about an industrial equipment uh fluke is useful because it is pretty good quality and also uh it keeps the health and safety narcissists off your back because they see the fluke and they say oh well he must be a professional so very similarly inside but note how are the two fuses one of them is soldered in this is a five amp fuse and this one is in series of that shunt there that also has a sleeve over it and that is just an extra layer of protection in case someone does poke the leads in they're also ceramic fuses which means if you do have an instant if you were to poke it into a distribution board and short it out then most likely these ceramic fuses would break the the fault current i still don't recommend using for that uh this one the fuse that says quick flow 500 milliamp but again it's a ceramic fuse very good it's just that little nice feature it's a proper peeper it's a got this extra fuse it just makes this a pretty good meter it does mean that this one this does 10 amps but this one only does 5 amp that's probably because they're reaching the cable and the fact that this one does actually comply with british regulations because it's from a prominent supplier cpc is part of farnell as part of a element 14. but there we go these meters don't be ashamed of these meters they're absolutely perfectly fine they're a very good starter meter but as you get more into electronics you may decide to go up market and choose something a bit posher or with other features like capacitance and things like that but as a starter meter these little ones are absolutely perfect

Channel: bigclivedotcom

Views: 103,188

Rating: 4.9695172 out of 5

Keywords: how to use, cheap, multimeter, meter, electronic, hobby, beginner, starter, first, fluke, cpc, farnell

Id: -QDW0LRQVrY

Length: 23min 12sec (1392 seconds)

Published: Sun Oct 03 2021

Reddit Comments

[u/nemom]

From the description:

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Your first multimeter can initially seem a bit daunting with all the modes, but the only way to learn is to get one and play with it. I damaged my first meter when I was young by using it on the incorrect range. You can damage these cheap meters, but at the cost you don't have to worry about it too much.

I probably made this video too long and complicated, but it's useful to know how things work as well as how to use them.

The very cheap meters sold for around 5 $/£/€ are usually pretty accurate for their cost and very usable. Once you've mastered using one you can move up to something with more features or more suitable for industrial work. These cheap meters are NOT suitable for poking around in distribution boards or industrial equipment with high fault current.

Meters have a category rating as follows:- Cat I - electronic use (these cheap meters) Cat II - electrical appliance, but not fixed wiring or distribution boards Cat III - general electrical maintenance in panels and machines Cat IV - utility level work with very high fault currents

For industrial work I recommend Fluke as it appeases the clipboard warriors. There are many other brands suited to industrial use too. Beware cheap meters with fake category ratings. The Fluke meter in the video is an original American made unit, and was my first ever real industrial meter. It cost a lot, but has lasted well.

I recommend getting these meters from a prominent supplier in your country to ensure they comply with local regulations. The one I demonstrated is from CPC/Farnell and definitely better quality than the eBay imports.

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