Important Multimeter functions?

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rmeldo

Senior Member
Hi,

This might be of interest to others as well.

I am trying to choose a multimeter that will serve me for a long time and I am trying to balance price and features. So I am asking for people's opinion on what features a multimeter should have.

I am not trying to choose a cheap one. I would like a fairly complete one. However if there is a function which I could expect to use only once in ten years and it it is expensive to buy then I will happily discard it.

I have seen on this forum a 2 channels oscilloscope and I will probably get one, so I don't need those features in a multimeter.

Also I am sure that things could be measured with a picaxe circuit, but if I am in the middle of debugging a project it would be impractical for me to put it aside, build my own instrument, and then go back to the original project.

Here is a list of features that multimeters could have, according to the Digikey.co.uk website:

Volts AC/DC
Amps AC
Ohms
Temperature
Continuity
Diode test
Hertx
Farads
THD (I don't even know what this is)
dB
Inductance
Logic
Transistor gain
Transistor leakage


Could people give their opinions? Also advice on specific brands/models would be welcome.

Thanks

Riccardo
 
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Rickharris

Senior Member
Volts
Amps to 20 amps
Frequency can be useful

temperature reading is useful

I have never used the transistor or diode testing functions on the multimeters I have used.

As an addition get good test leads
 
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BCJKiwi

Senior Member
Recently purchased a QM1538 which seems to be readily available - got mine from Jaycar.

Has all you want (and all I can see I'll ever need) in a multimeter.
Popped a few fuses measuring amps as the normal Amp range is up to 500mA so the 10A range needs to be used if there is a risk of > 500mA being measured - (500mA is less than my old meter).
Also has basic data logging and the thermocouple included.

Recently had issues with car battery and the Auto electrician was very scathing about my 'cheap' multimeter insisting that it would be way off but when he hooked up his $$$$ Fluke special Automotive meter, they read exactly the same - good enough for me!

Manuka has also recommended this in the past (for data logging I think).
 
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westaust55

Moderator
THD = Total Harmonic Distortion - but is it THDv or THDi ?

But unless you are trying to find the level of waveform distortion caused by a motor into the rest of the circuit (for example) then it is not likely to see much use.

Volts, amps (to at least 10A) and ohms are the functions I use. One of mine has transistor test mode but never been used.
 
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hippy

hippy

Ex-Staff (retired)
Continuity (audible), Resistance, Volts AC/DC, Diode test, Amps AC/DC, are all I use ( in order of most used ) but would like to have Frequency, Capacitance, Inductance. The rest I've never had a need for.

You can get all that and more in a reasonably cheap multimeter. Hold and Auto-Range are also handy.
 
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BeanieBots

Moderator
Your choice really depends on how far you want to take things and if you want to do general, analogue or digital.
I'd go with Hippy's comments for the bulk. Especially continuity (audible).
Accuracy is important. At least 3.5 digits but more importantly accurate.

The rest is of little use. Just about nobody uses hfe. If you can't read the product number and look it up in the datasheet, put it in the bin! If you need the exact hfe of THAT tranny, your design is wrong!

Current is nice but not essential. I once did a survey at a large company where they used Fluke 77 and Fluke 79 as standard. Out of the 80 odd that I tested, only 3 had an intact fuse. That's because many people forget to switch back to volts after current and then measure volts which pops the fuse. A replacement fuse will cost ~£5:eek:

Capacitance and inductance are nice but not very accurate unless they are dedicated measuring instruments. Again, like hfe why would you ever need it.

In short, 3.5 digits, auto-range, Continuity,Volts,Resistance,amps,diode-drop.
For all else, get a dedicated measuring device if you need it.
Get one decent multimeter and another cheap one.
Also worth having a good analogue meter if you want to play with much 'control' related electronics.

EDIT:
The one suggested by Boriz looks like a good choice.
Good accuracy/price and all the important bits.
Your second meter should only cost about ~£5.
 
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Pekari

Senior Member
rmeldo, I have in using AC/DC ampers up to 20 A (Fused), hFE, Capacitance, beeper etc. all funktions which I have in multimeter, but I don't have all funktions which are in your list.

Some multimeters have a memory (hold button) and light in display but I don't know is those necessary.
 
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ercotronic

Member
BeaniBots has touched on a very important factor. Imagine if those 80 meters he had tested were 'cheap' meters without a fuse in the current testing loop, being in an industrial setting means that the meters were probably being used at single and three phase mains voltages. The instantaneous fault current would probably run into many thousands of Amps
and you would be relying on whatever protective device lay 'upstream' of your meter to protect you. The meter in your hand could turn into a plasma cloud and be the most spectacular thing youv'e seen.......or more to the point would ever see again!!.

If there is a remote possibility that the meter will be used at mains potential do yourself a favour and get a fused meter. The higher the category rating the better the meter should be in terms of safety.
 
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Rickharris

Senior Member
Not sure how cheap you mean but the £5.50 meters I quote above are fused in current ranges. - Kids generally blow them as BB says.

The good old AVO 8 had a mechanical resettable breaker - Popped it many times :)

Even in your worst case scenario there are plenty of componants inside that act as a fuse!
 
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manuka

Senior Member
It's horses for courses guys. Although crazy money can be thrown at professional DMMs,they may well keep working in difficult situations (dropped from a rooftop/ being run over by a sparkies van/ zapped by 11kV etc). For general electronics work those Jaycar QM1538s are still my favourites however, although (after ~ 6 years) they're apparently being runout. But even a DSE US$5 cheapie can do the job in many cases- see my one at work => http://www.instructables.com/id/S5Z2VGDFMMCVR28/ Stan
 
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Dippy

Moderator
Good point, though I have yet to see a multimeter without a fuse?
Ebay cheapies maybe? Dunno, I'd be surprised.
I have however seen idiots trying measure volts when the DMM is connected up to measure current. Oooh nasty! And a fuse doesn't cancel out moronity :)

All the points posted above are very valid.
Before I disappear again can I just add a couple of things as 'food for thought'.

1. Practicality.
One of the things that drives me nuts (as I am impatient) are the DMMs that require you to:-
a) Have to unscrew a panel to change batteries.
b) Ditto fuses. I right pain in the arm esp when they are tiddly pozidriv screws.

2. Quality.
For general purpose rough-stuff I'm sure there a multitude of Cheapies out there that are good enough and covered in functions to suit most tasks. Jack of all trades.
But if you want quality and a machine you can rely on to give accurate (as opposed to 'precise') results then, I'm afraid, you will have to save up your pocket money and get a 'proper' make. Or a make that is supplied by the Big Boys like Farnell etc. Remember, they don't want warranty hassle, so , generally, they will have selected good gear. Just look, you can always buy elsewhere.
Many suppliers are just cheap box-shifters and don't give a hoot.
I'm not saying, however, that you have to pay a fortune for something good. Just be canny.

3. Fuse sizes.
Some DMM have fuse holders for fuses that are either expensive or harder to get. Check it. I think I have a Maplin Gold like that, not sure.
 
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Andrew Cowan

Senior Member
http://www.maplin.co.uk/Module.aspx?ModuleNo=4393&&source=14&doy=2m11

I have that Maplins gold one - can do everything want. I like the capacitance feature - it is handy being able to read the capacitance of tinyy capacitors that don't have their values clearly printed on them.

The only downside is the main fuse (10A) is a huge thing that costs £4.99. I use a £2.99 multimeter for measuring high current, and this for measuring anything more.

I once shorted a 7.2V r/c battery across a cheap (unfused) multimeter on the current mode. It lit up and smoke poured out the side, so I unplugged the battery. It still works fine, though - it doesn't seem to have been affected.


Volts AC/DC - all multimeters have this. Any expensive multimeter will probably be accurate enough.
Amps AC - I have never needed amps AC- all multimeters have amps DC.
Ohms - All have this - make sure it has a continuity test. My multimeter can measure up to 2000M - I have never needed more than 20M.
Temperature - I use my cheap multimeter for this - it is fun, but not really needed.
Continuity - You NEED this.
Diode test - Never use it - apparently you can test some LEDs with it, but I use an LED tester.
Hertx - I use it occasionally, but a scope is much better.
Farads - I like this for measuring capacitors which have their values written on them in code (the ceramic ones).
THD - No idea
dB - Wy would you want this?
Inductance - I have it - it is useful when you take a coil out of some old equipment, eg a computer, and you want to file it.
Logic - Not a must - most people use a separate logic probe. I don't have one - I tend to just use a voltmeter.
Transistor gain - I have it - I never use it. Use the dtatsheet!
Transistor leakage - Again - I don't think I would ever use it.

Andrew
 
hippy

hippy

Ex-Staff (retired)
Maplins sell a whole range of multi-meters ...

http://www.maplin.co.uk/Search.aspx?menuno=11808

The one I have is the second blue one (GW18U). If buying now I'd probably choose the one below for the Capacitance and Frequency measuring.

Mine's lasted over a decade and has been very reliable ( still using the original battery ! ) so a little extra cost isn't much over that period of time. Sometimes more isn't always better; look at how it works and how it feels as you'll be using it a lot. I don't like the third blue one because it has a slide-switch on-off, my personal taste, others may prefer it.

Don't forget that Tech-Supplies carries a reasonable cost DMM (TOO030) so it's easy enough to add one to your next order !

http://194.201.138.187/epages/Store.storefront/?ObjectPath=/Shops/Store.TechSupplies/Products/TOO030
 
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eclectic

Moderator
Not adding much, but ...

you will definitely need to measure two or more values concurrently,

1.Get a couple of cheap analogue meters, so that you can see changes and trends.

2.Get a couple of cheap digital meters as spares.
Frying a Fluke is a disaster! Zapping a cheapie is less worry.

3.Find the meters with the cheapest fuses, then buy a pack of fuses.

4. Following Rick's Leads(!):

Either buy a selection of leads, for example:
http://www.rapidonline.com/Cables-Connectors/Connectors-Single-Pole/Test-Probes/Professional-test-probe-set/67870

http://www.rapidonline.com/Cables-Connectors/Connectors-Single-Pole/Test-Probes/PMS-0.64mm-Surface-mount-test-equipment-set/72769


Or, make your own, using connectors and flexible silicone cable.
Just one example of many:
http://www.rapidonline.com/Cables-Connectors/Connectors-Single-Pole/Test-Probes/KLEPS-30-Safety-test-probes/72765

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alband

Senior Member
Currently I'm using this:
http://www.maplin.co.uk/Module.aspx?ModuleNo=44679
and confess I have used the transistor function (for fun).
One very useful feature it has is measuring resistance down to 200ohms - doesn't sound useful, but at that scale it has to provide 3V (low ampage though) to get an accurate reading i.e. it's great for testing LED's, i've used it more that the voltage function. Make sure you get one with a very large "ohmage" (is that right?) range.

This on hasn't got capacitance though and I've needed it on occasion.
It also ironically but so usefully has a low battery indicator.

Let us know which one you settle for.
 
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rmeldo

Senior Member
What a good and comprehensive discussion

Thank you all very much.

This is turning us to be quite complete.

It looks like the not common features (the one that force a either/or choice) are:


AMPS AC: not that needed unless you do work with the mains or you want to check the power consumption of your microwave (say)

TEMPERATURE: I definitely need this for my current project and afterwards I can see the need for it every now and then.

CONTINUITY - NEEDED. and it must be audible
Diode test - Never use it - apparently you can test some LEDs with it.

HERTZ - Occasional use. (in motors/generators, RC circuits)

FARADS - good for measuring capacitors which have their values written on them in code (the ceramic ones).

THD - This is to do with

dB - (I presume sound) Very specialised. Why would you put a mcrophone in a multimeter? A dedicated instrument might be a better choice. (but I might be missing the point here)


INDUCTANCE - it is useful when you take a coil out of some old equipment, eg a computer, and you want to file it. This is definitely something which appeals to me. I am planning to do some salvaging as my company is getting rid of 5 old PCs and I am planning to open them up and see what I can scavenge. I will try and get this function


LOGIC - Not a must - most people use a separate logic probe. could also just use a voltmeter.

Transistor gain - Seldom (never) used. Use the dtatsheet!
Transistor leakage - Again - I don't think I would ever use it.


A point that was made is the PRECISION. I agree and I am sure there is a trade off between number of functions/price/accuracy.

Also the cost of spares should be looked at (fuses) in terms of "cost of ownership".


One feature which wasn't on my original list is the connectivity to a computer.
Could anyone elaborate on this?

Also, what about auto range? Nobody mentioned it. Should I conclude it is not that important for hobbists?

Someone also mentioned a good set of test leads. Any advice? What about "crocodyle" style ones?


Regarding candidate models for purchase I looked at the ones suggested in the forum, but also at the digikey website.

What do people think about the Amprobe ones, the AM-240 (£24.61)and the 33XR-A (£49.25)?



Again,

Thanks to you all

Riccardo
 
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eclectic

Moderator
riccardo.

Where are you?
Then people can give you more specific product advice.

And leads: what do do want to connect to?
"Crocodiles" may be too big.
Do you require SMD connectors, or hooks or pins or ......?

e.
 
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Dippy

Moderator
"A point that was made is the PRECISION. I agree and I am sure there is a trade off between number of functions/price/accuracy."

And , as you know, Precision DOES NOT necessarily = ACCURACY.
19.2344555546464 Volts is PRECISE.

But as Stan pinched my Horses For Courses I had better agree.

How 'good' do you want? How big is your wallet?
Cost does not necessarily equate to quality I agree, but there is a higher probability that it will :)
If you want a single instrument to be 'really good' do you buy Fluke or one from the "50p Beijing Anonymous Multimeter Company Ltd"?

Do you want something you can trust or something that is just 'good enough'?

If you designed an MPPT power supply , and had some problem and posted here that you measured 3.6volts, do you want to be confident that the figure is good?
IF so, spend the extra, unless you have chum with a good one to compare.

If you do AC measurements will you need true RMS?

I've never heard of Amprobe. They may be fine. Buy a few and tell us. I daresay there are gallons of rebadged stuff from the same factory e.g. a bit like Draper, Roebuck. etc.

I like floppy 'silicone' test leads, but that's my problem :)

But that business with piddly-Pozi unscrew panels for battery and fuse chang drives me mental. In my collection I have 3 Maplin ones, they are like that with harder-to-find fuses and it gets on my nerves.
 
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BeanieBots

Moderator
Auto range IMHO is ESSENTIAL. Nothing more irritating than having to let go of something you are tesing because the meter needs to change range.

Fuses: These cost £5 for a reason. They are ULTRA fast. They save the meter when applied to volts on current setting. Fit a 20A car fuse (as suggested in one post) and the current sense resistor will evaporate long before the fuse even notices it is over-current. It is possible to 'modify' the fuse holder to take smaller (physically) fuses which are a bit cheaper but make sure you use the correct type.

Measuring inductance: Only useful if you make your own passive cross-over networks for audio. Most DMMs measure inductance at 1kHz. What frequency do you need the inductance to be at? Use a dedicated meter if this is important to you.
PC power supplies only have one inductor and it's 100uH. (saved you the bother). The rest of the magnetics is Transformer and common mode choke. The only use the transformer would have is in a similar psu. Cheaper to buy a new one. The common mode choke is 200uH @ 50/60Hz.
Making your own inductor/transformer. Probably get more accurate results from the datasheet and counting the turns.
RF inductors: a DMM cannot measure these.

Capacitance: Maybe. Better to learn the code. Same for resistors but Ohms is very useful feature, especially a low range for testing cable resistance, dry joints.

Leads: First thing I do with cheap meter leads is cut off the naff probes and replace with quality clips.
 
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Dippy

Moderator
Autoranging... very good point BB.

"These cost £5 for a reason."
- yes, there sure is a reason and it ain't the speed.
Other types of fast fuses are available for pennies.
I cannot be convinced it is anything but a ripoff. (Don't try, check out the 'trade' prices).
 
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papaof2

Senior Member
Amprobe is a US brand of long standing. They were there in the early days of clamp-on analog AC ammeters.

The meters from 30+ years ago were very durable stuff. I rebuilt one that a refrigeration repair guy ran over with his van (probably at least a $150 OOPS! in 1972 dollars). I replaced the broken parts of the Bakelite case and straightened the meter needle. The meter is still working. It has AC amps ranges to at least 30, plus 300 & 600 AC volts ranges (maybe an ohms range, but I've never used it for anything but AC volts & amps).

John
 
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Pekari

Senior Member
I will NOT recommend a multimeter with auto range and WITHOUT manual range. Sometimes you can't measure a value if it is changin range all the time...:(
 
hippy

hippy

Ex-Staff (retired)
I think one thing very clear is that what's essential and what's an irrelevancy ( or even a waste ) depends very much on what the person using it is going to be doing or needs.

Most of my use is in "confirming" rather than testing or development so I don't really have a need for highly accurate and expensive kit. I'm usually just wanting to check if the resistor is orange-red-brown or brown-red-orange, if it's 47uF or 4.7uF, which is the anode of a LED, does this connect to that, and is it something like +5V going into a PICAXE.

One feature which wasn't on my original list is the connectivity to a computer.
Could anyone elaborate on this?

You're usually going higher up in price so it's a question of does it offer anything you need, and is it worth the cost ? That depends on what you're doing. It's never been anything I've needed.

Also, what about auto range?

Useful, not essential IMO, but does save messing about. It's also handy if there are icons where a 10K resitor shows as "10 K", not as 0.100 and you have to work out what that means dependig on range selected.

Someone also mentioned a good set of test leads. Any advice? What about "crocodyle" style ones?

Really depends on what you are connecting to. Handy for when you want to keep 0V in place and test voltages elsewhere ( a croc-clip lead from the probe does that job as well though in most cases ).
 
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Andrew Cowan

Senior Member
I find my non auto-range meter great - I don't like auto range meters, as the decimal point keeps changing. With non auto range meters, you change it yourself.

Probes - I have two sets - one with sharp spikes - usesful for measuing on PCBs and other cramped spaces, and another set with croc clips - useful when connecting to wires. I find even minature croc clips too targe for connecting to PCBs and IC pins etc.

You definitly want one set of spikes for poking at IC pins.

Andrew
 
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papaof2

Senior Member
"One feature which wasn't on my original list is the connectivity to a computer.
Could anyone elaborate on this?"

Some meters have an RS232 port and can send readings to the serial port of a PC. The next level up of "connected" meters can be controlled by the PC: set the range, take a reading. Great for monitoring changes over time (voltage stability of a supply, current draw of a device, resistance change of an LDR during the day, etc).

Even Radio Shack sold serial-enabled DMM in the distant past - along with the ProbeScope, which had a tiny LCD display on the side of the probe and a serial link to a PC for displaying the waveform (bandwidth might have been 2MHz).

John
 
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wojeepster

New Member
I use multimeters for automotive usage, house wiring, and electronic kits and things and I am in love with my fluke 177. It does almost everything. It has the usual ac volts, dc volts, HZ, Ohms, Capacitance, diode check, ma, and Amps 10A, it also has min max avg, hold, range, backlight and a bargraph so it can work as an analog meter when checking for example a throttle position sensor, I also have an amp clamp that goes with it so I can measure up to 400 amps ac or dc. about $200 without clamp. I use a cheap $3 meter to check transistor gain I bought at harbour freight. fluke 179 has temp probe. It is hard to go wrong with a fluke.
 
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Dave E

Senior Member
Personally, I do not like autoranging. You should know the ballpark range of anything you are testing. Also, if you don't ALWAYS look at the range every time you look at the display then you are only assuming that you know the range. Bad idea IMHO. That assumption has bitten me more than once.

Same thing with continuity tests. They may be quick and easy but what are you actually looking for and what is the meter actually telling you. Use the resistance measurement then you know what you are measuring. Are you reading through a motor winding or relay coil then to ground or reading straight to ground? Some continuity testers will read the same for both of the very different situations.

I got started with a Fluke. Used it several times a day, 5-7 days a week for almost 13 years. Used it with 480 Vac 500 amp (with a clamp on attachment), 5 Vdc, 3000 Vdc at miliamps (with high voltage attachment). I have dropped it, kicked it, steped on it, got it wet, cat barfed on it, took it apart to clean out the barf, left it in my car for a year... It is now over 20 years old and it worked today just like the day it was bought. It has never needed repair. I have since purchased another one. It is 10 years old. I have used others but have always gone back to the Fluke. And no, I do not or have not ever worked for Fluke.

As for accuracy, I can make an accurate volt meter with about $10 worth of parts but I will check its accuracy with my meter.

I do agree that an analog dial type meter is handy when viewing changing signals. A DMM just doesn't hack it in that situation.

Which ever meter you choose. READ the manual and understand it. Especially the input impedence. When measuring the voltage of a home receptacle it is not too important but working with electronics, it is very important. Get a meter with at least 10 megaohm impedence. This is the resistance you are putting in parallel with any curcuit you are measuring. Remember that. It will save you a lot of hair pulling and head scratching later.

Even if you must save up a while longer to get a good meter, do it. Buy you a good one and it will last your life time. And remember, you will be counting on that meter to tell you what is going on in every circuit you test so get a meter that you will have confidence in.

If you are like most people that are comfortable around electricity you will be called upon to figure out why the toster won't work or if the car battery is dead or not or which breaker feeds which receptacle or how many amps does the washing machine pull or is the heating coil in the hair drier bad or is the flashlight not working because the batteries are bad or is the bulb bad or is the switch bad..... So get a meter that does read AC as well as DC in both amps and volts. You will need it eventually.

Sorry if this sounded more like a rant. Its just important to get a good meter. It will be your eyes into electricity.

Dave E
 
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rmeldo

Senior Member
Thanks everyone.

I think I have more than enough information to make my decision.

Now the difficult part comes: reading manuals, comparing specs and prices.

I write from the UK, Brighton. There is abranch of Maplin in town (just found out). I will certainly pay them a visit.


Riccardo
 
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BeanieBots

Moderator
Small world. I used to use the Brighton Maplin but they've balls'd up the road system so much now that it is quicker & cheaper to buy online. I'm about 4 miles from that store!
I think there's still parking in Shoreham. Only a 5 mile walk:mad:
 
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boriz

Senior Member
Good luck finding what you want. I can’t remember the last time I went to a Maplin store and got what I needed. I ask for 10 transistors, they have only 3, I ask for 10 resistors, they have only 4, etc..

They used to offer to post the remainder for free, now you have to pay, (Scam!). Also, the catalogue used to be a wonderful resource, full of useful info, data, and even application circuit diagrams. Now it’s more like an Argos catalogue.

BTW. I used to use the transistor tester on my meter frequently. Sometimes to establish the pinout, and also to compare the measured hfe with the expected hfe so I can get an idea of the transistors condition. I say ‘used to’ because I now have a better alternative. I have two testers from here. This component analyser and this LCR meter. Both dead useful. Add that to the 2 dual-CROs I have and I’m ready for just about anything.
 
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moxhamj

New Member
Re Dave E "I have dropped it, kicked it, steped on it, got it wet, cat barfed on it, took it apart to clean out the barf, left it in my car for a year".

One day I will find a Fluke in my xmas stocking *sigh*.

When I was a kid I went into an electronics store and the salesperson was demonstrating how robust the fluke was, opened the shop door and chucked it out on the road, whereupon a car drove over it. It still worked! Not sure if that one went into the "shop soiled" bin afterwards.

Better value than the Monty Python gentleman's suit. You can spill red wine on it. You can crush it. You can rip it. But it'll ruin it.
 
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Marcwolf

Senior Member
One hand feature that I have used on my unit every so often is data logging.

My multimeter has an RS232 interfacer that I can plug into the computer I used for my PICAXE programming. I have found it handing for monitoring voltages and discharge rates over a period of time..
 
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inglewoodpete

Senior Member
Auto Power Down

After speed reading this thread, I can't see a mention of 'Auto Power Off' or 'Auto Power Down'.

That's a feature that my next multimeter must have.

I'm not a fan of autoranging either but it has its uses for steady voltages/currents etc.
 
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