EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: wintech on July 22, 2019, 08:15:35 pm
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Why do I need more than 1 multimeter?
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oh
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It's not unusual to want to measure more than one voltage or perhaps a voltage and a current all simultaneously
Take the average LED - it has a very specific characteristic curve of voltage versus current. You might want to rig up an experiment to measure these values and plot a graph like the one in the datasheet.
I have 2 bench model DMMs plus 3 handhelds layig on my bench plus some more on the shelves in the closet. I think WANT got ahead of NEED but that's not a problem.
Three meters is a realistic number.
Transistor base voltage, base current and collector current. Maybe another for emitter voltage if there is a degeneration resistor.
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On a practical basis, maybe you want to measure both the input voltage and the output voltage of a circuit? Hard to do with a single meter.
But once you get a second one - you'll want a third. And a fourth... and by then you will have heard of some of the classic vintage handhelds and bench meters, and you'll want some of those, and next thing you know, you will be posting in the TEA thread under the Test Equipment section.
And of course, multimeters are just a gateway drug - next you'll be collecting oscilloscopes, signal generators, and all sorts of gear. Heaven forbid you discover nixie tube gear...
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Multiple parameter monitoring.
A perfect example: Input line regulation on a voltage regulator. Or load current regulation also on a VR.
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Thanks for the advice! :)
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The correct answer is you do not need them if you asked that question.
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I needed at least 3x MMs, to reconfirm any readings with MM. I actually have 5x MMs.
Yes, I do confirm at least 3 times with different MMs for each readings. Recently 5x times. Because any of them might go faulty.
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Sometimes the type of work also defines having more than one meter. For example, if you live in a house and have a very good and high precision multimeter for electronics work, you will rarely want to take it to inspect something outside on the dirt, mud or wet area - for that task a more suitable meter can be a simpler, less precise and perhaps water/dust proof meter.
That also does not count the occasional need for measuring high currents on regular equipment - in this case, a current clamp is better suited for the job.
Obviously that, as others have mentioned, as time goes by the more the merrier. :)
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It can depend what meter you start with. If you start with a handheld, you *might* be able to get by with just that since it can easily follow you to whatever you're working on.
If you start with a bench meter, you're more than likely going to still need a handheld since not everything you'll want to measure will be at the workbench.
I managed through decades of hobby fun with just a handheld, albeit the best one I could afford when I bought it. I only recently added a bench meter for the convenience of not having to unwrap cords, find a place to set the meter, etc.
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I have a whole range of meters. I have a couple old analog meters that I got decades ago when I was starting. I hardly use them any more but they are like old friends and they keep me company at my work bench.
I have a bunch of cheap meters which I got because they were cheap and they are good enough for basic work with batteries or mains where I do not need precision. And I have some better ones, including a massive bench meter which is more useful for precision work.
I find it useful to have a cheap meter at hand rather than have to go up or down two floors to get a meter just to test a battery or other simple task.
A couple of months ago I was doing some mains work and I forgot to change ranges and I blew up a cheap meter. Thank goodness for that.
Yes, I could get by with fewer meters but I find it convenient to have a bunch of them with different qualities and capabilities.
I find it amazing that there are households with no tools. I feel I should have a basic tool kit in every room of the house.
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In truth you only need one multi-meter. All you have to do is move the probes around to measure voltage differences. Same is true for current, just use appropriate shunt resistors and measure the voltage across the shunt resistor. Granted it takes a bit longer but it still takes time to read voltages and currents from several multi-meters and you can always get a ball park measurement with a scope.
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The reason you need two multimeters, is that with three multimeters you can verify (to some measure of reliability) that all four of them show consistent values for the same measurement, and that the fifth and sixth are not too far off.
To be honest (and I'm not TEA yet!), I need two because I'm likely to break one by doing something dumb, and because I occasionally want to measure two voltages or a voltage and current at the same time. Plus, a third, cheapie one, would be nice to take with me, when I go meet friends about electronics, so I can keep my good ones at home.
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One for the lab. One "safe" one for the work on mains voltages. One to keep in the car. One in the kitchen drawer to check batteries. One for the wife to destroy. Another for the kids to destroy. It just goes on and on. Fortunately most of these "needs" can be met with the free or nearly free low end meters.
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Why do I need more than 1 multimeter?
Because I can´t remember where I left the other one. :-DD
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In addition to all of the above reasons, you will probably find that there are some ranges and/or ratings that you will need that are not found on one meter or that if they are, that two or more separate meters can cover this for a fraction of the cost.
The correct answer is you do not need them yet if you asked that question.
FTFY ;D
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If you have to ask why you need something then you probably don't need it. When you come across a situation where you need multiple meters you'll probably know.
Personally I have a bench meter and a handheld and that's all I regularly use. I also have an old Nixie tube meter I pull out once in a while just because it's cool and I keep a Harbor Freight freebie in my car for emergency use.
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If you have to ask why you need something then you probably don't need it. When you come across a situation where you need multiple meters you'll probably know.
I still think it is a valid doubt. For at least two decades I got by with a single multimeter, making voltage and current measurements one at a time. Due to the cost of these instruments back then, it never occurred to me to even consider buying a second one. I certainly needed it then, but I couldn't wrap my head with the idea of having more than one (not to mention a Fluke). Only when I moved here to the US (testgear heaven) is that I actually found out the price point intercepted my comfort level. I now have about 20: some inherited from my late father, others bought on the cheap, with several old crushes (Flukes 8020A, 8060A) while others have unique features (LED, 4 wire measurements, 500000 counts) that make up for interesting uses.
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... I now have about 20: ...
:o
Is there any chance now, that you've properly developed a unique swimming style in your sea of DMMs ? :-DD
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Why do I need more than 1 multimeter?
One to perform a measurement. Two or more to make simultaneous measurements. It can also be handy owning different models with different features or accuracy or having a spare as a sanity check (https://en.wikipedia.org/wiki/Sanity_check) for measurements.
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Well, it's one for the money
Two for the show
Three to get ready
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and four for the cat ... or something...
You can burn my house
Steal my car
Drink my liquor
From an old fruit jar
Well do anything that you want to do
But uh-uh, honey lay off of my DMM.
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... I now have about 20: ...
:o
Is there any chance now, that you've properly developed a unique swimming style in your sea of DMMs ? :-DD
:-DD Yes, that sounds really a great idea!
I have a strong suspicion these DMMs mate and have offsprings when I leave them all together in their box. I couldn't have possibly bought so many! ::)
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Why do I need more than 1 multimeter?
Why not?
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Only one meter ???????
Are you sure you belong on this site ? :)
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Well there is still a benefit to having only 1 multimeter. When you measure something being 10V you accept it as being 10V
If you have 2 multimeters and one shows 10V and other shows 9.998V... so which meter is accurate. Now you need a 3rd one to check, but then that meter shows 9.999V. And this is how volt nuttery starts.
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... And this is how volt nuttery starts.
Starts - and continues .... (and, no, it never ends.)
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Well there is still a benefit to having only 1 multimeter. When you measure something being 10V you accept it as being 10V
If you have 2 multimeters and one shows 10V and other shows 9.998V... so which meter is accurate. Now you need a 3rd one to check, but then that meter shows 9.999V. And this is how volt nuttery starts.
With that logic, why not have none? You just estimate and you can't be proven wrong.
Three. That is my magic number. Normally, I measure with my lone "good one" (UT61E). The other two are cheap DT820's. They are generally for when I work with power related. In those cases, I like to know Vin-Vout, or V & I at the same time. I also have a few ADS1115 boards (16 bit DAC) along with a few INA219 boards (12 bit DAC) that can be hooked up quickly to take on the V&I measurements.
As to volt-nuts... I think I recovered from it. I came to accept - well, until I get a 64 kilo-bit DAC with +-1% accuracy, I would not be truly happy with the results. But some old German guy call Heisenberg or something like that - this fellow poured cold water on the idea of really really really accurate measurements...
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It's good to have at least two multimeters, for example to measure input and output voltages , or to measure current while also measuring voltage.
You could also have two multimeters for various functionality you might need.
For example, my main multimeter is a Uni-T UT61E. However, I also bought a Uni-T clampmeter, to measure AC and DC currents without breaking the wires that power devices. As a side functionality, it's also a 2000 count multimeter capable of measuring voltage, resistance, continuity... and it's good enough for some basic measurements.
Then, I also bought a LCR meter, because I wanted to have something capable of measuring inductors... and this one can also measure voltages and resistors and so on...
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The correct number of multi-meters to own is always n+1, where n is the number you currently own...
For more quality advice, visit the TEA thread... :-+
Additionally, in the first sentence above, you can replace "multi-meters" with any of ( oscilloscopes | power supplies | LCR meters | spectrum analyzers | logic analyzers | signal generators | rubidium standards | network protocol analyzers | data acquisition mainframes | pulse generators | insulation testers | modulation domain analyzers | etc) and it remains equally true. >:D
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The correct number of multi-meters to own is always n+1, where n is the number you currently own...
I would like to challenge that. My current status is at n+2.
In addition to my current holding, I would like to add a bench meter with 4 wire measurement and something like the Uni-T 210E for a DC current clamp meter. Why? ... Because I don't have them. ;D
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When measuring a component, if reading is out of expected value, then I wonder, if it s it the component or MM. Then I want to try with as many MMs as possible to confirm which is at fault. More MMs, merrier the confirmation.
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Some situations could require 5 DMM's and perhaps a webcam to record simultaneous event data. More never hurts (unless your significant other knows how to drop-kick..)
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While i do probably have too many multimeters i do agree that the actual useful benefit of having more does tend to fall off after the 3rd one.
Having 3 of them lets you notice if 1 of them is going out of calibration because you will see 2 meters agreeing and one disagreeing.
Also 3 meters is the minimum for reasonably measuring the efficiency of a power supply. You need 2 meters to be current meters on the input and output. Those can't be be easily disconnected and moved around because moving the probes away breaks the circuit, while shorting the circuit back together affects measurement because the meter was causing a voltage drop different to the short. But the voltage can be a single meter since you can just poke the input and then poke the output with the probes without affecting anything.
But there still are reasons to go to >3 multimeters. Like measuring power supply efficiency without having to move a multimeter around, or having multimeters with extra special features for a given task. Like able to measure very small voltages or currents, having lots of digits (like 6.5 or more), having high impedance inputs, having a really nice continuity beeper in it, being small and rugged for field use... etc. You can't get all of these features in one meter
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Only one meter ???????
Are you sure you belong on this site ? :)
I thought two are minimum for signup on the forum....
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I agree multiple meters are useful to measure voltage and current simultaneously.
So why can't they build a meter that can do both at the same time?
And why would anyone need more than 1 scope? >:D
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I agree multiple meters are useful to measure voltage and current simultaneously.
So why can't they build a meter that can do both at the same time?
And why would anyone need more than 1 scope? >:D
Because using several MMs are good fun, and feel great. You can also compare readings of different MMs for the same component. :D
And not all MMs have all the capabilities in one. Some MM do not have capacitance, some dont have NCV, some dont have hFE ... some MMs have Capacitance reading limitation to 1000 nF ..... blah blah.
Having more than 1 scope gives more flexibility. I have 1 base scope, and 3x portable ones. I carry the portable ones to the shed, car and out in other locations in my pocket or bag. Cannot do that with 1 desktop scope powered by mains.
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All the above reasons, and MORE* coming (*meter/s in your 'posession')
and do you really need another phone or the latest shiny adware magnet one? Meters are more fun, survive drops better and no Facebook BS
My two probes worth: different meters sport different features, Min Max and Low-Z and Auto Low-Z I find very useful in many iffy situations,
basic logging is nice too, to keep unattended tabs on a tedious or intermittent head banger, |O
I find owning a 'few' meters (nose growing.. :o) with ALL the various functions scattered amongst them,
is a cheaper and better bet, than having one or two expensive 'all in ones', sometimes with too much smarts on board ::)
and not really the 'jack of all trades' you think you have
and here's an important FYI for the pocket > some cheaper decent meters excel at being sacrificial,
i.e. they just won't spark out or die like expensive ones tend to sometimes do
I think three multimeters plus a clamp meter is a good minimum to have, and cut off point (good luck with that..)
Upon getting there, the meters photographed with the owner in a mug shot holding up today's newspaper,
then emailed to EEVblog Admin as a requirement to join the forum ;D
The correct number of multi-meters to own is always n+1, where n is the number you currently own...
I would like to challenge that. My current status is at n+2.
In addition to my current holding, I would like to add a bench meter with 4 wire measurement and something like the Uni-T 210E for a DC current clamp meter. Why? ... Because I don't have them. ;D
I keep meaning to get one every few months when I remember or see posts here about it, for those iffy AC and DC mA measurements
(and because I don't have one, therefore I plead guilty Your Honour, and throw myself at the mercy of the EEVblog Court.. :scared:)
and always the local oz sellers are either out of stock
or want $700 for one :o so when queeried about that, they reply it's currently out of stock but keeps the Ebay listing going = :wtf: + :palm:
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I'm off to check out the other post too > Re: Why do I need more than 1 oscilloscope?
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I just got a used Unit-e meter from a pawn shop for 7.50 usd. The milliamp fuse was blown but other than that it works good.
Miles ahead of the cheap Chinese 830 type meters.
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When you take a small boat to sea, you take one compass or three but never two.
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Why would one need more than 1 scope? Well you need a 2nd scope to fix the 1st scope when it breaks of course. ;D
Yeah its a bit harder to justify, but i do have a good reason for having two scopes. One of them is a high performance 4GHz scope running windows. While the performance is certainly nice there are down sides such as the inputs being more sensitive to damage, slow waveform update rates, slow boot times, clunky to set up, big, noisy, power hungry... etc So next to it i also have a old Agilent MSO6000. It might not sound as impressive at 300MHz and 2GS/s, but its a fast booting quiet scope with very good waveform update rates and is quick to set up. And because of that most of the time i end up using the smaller scope for convenience.
With how good digital scopes are getting its harder to justify keeping around old analog scopes around, but one wouldn't throw out a perfectly working scope right?
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Some of you need to visit this old popular thread -> Show your Multimeters (https://www.eevblog.com/forum/chat/show-your-multimeter!/)
Quote from an example post from that thread.
Courtesy of ModemHead, all used & repaired. :o
(https://www.eevblog.com/forum/chat/show-your-multimeter!/?action=dlattach;attach=67776;image)
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The correct answer is you do not need them if you asked that question.
This is great!
I was a car mechanic and you couldn’t have enough tools. Now my mechanic days are behind me but my love of tools and equipment is still strong.
Sent from my iPhone using Tapatalk
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Until you learn to use the one you have, you don't really need another one. Unless the one you have is unusable, of course.
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I was making test documentation for a ontified body, doing temperature test of a component, logging data. You can use specialised equipment for it, but DMM is just more versatile, and you only need the setup every once in a while. So I was measuring voltage, current, temperature with a soldered in thermocouple, ambient temperature with a PT1000. All with 4 calibrated multimeter, 34465A, every x second sample taken. Few pages describing the test setup, complete with pictures, architecture etc.
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All the above reasons, and MORE* coming (*meter/s in your 'posession')
and do you really need another phone or the latest shiny adware magnet one? Meters are more fun, survive drops better and no Facebook BS
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I'm off to check out the other post too > Re: Why do I need more than 1 oscilloscope?
What!??
Where's "Why do I need more than 1 oscilloscope?" :-BROKE >:D
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All the above reasons, and MORE* coming (*meter/s in your 'posession')
and do you really need another phone or the latest shiny adware magnet one? Meters are more fun, survive drops better and no Facebook BS
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I'm off to check out the other post too > Re: Why do I need more than 1 oscilloscope?
What!??
Where's "Why do I need more than 1 oscilloscope?" :-BROKE >:D
Well, since you asked for it ... >:D
(https://www.eevblog.com/forum/testgear/why-does-everyone-have-twenty-oscilliscopes/?action=dlattach;attach=201083;image)
-> Why does everyone have twenty oscilliscopes? (https://www.eevblog.com/forum/testgear/why-does-everyone-have-twenty-oscilliscopes/)
-> Do you collect oscilloscopes? (https://www.eevblog.com/forum/chat/do-you-collect-oscilloscopes/)
Words of warning, cause you may ended up joining the TEA (https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/) cult ... :-DD
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Anyone with that many oscilloscopes above, is past having to justify having them
to jealous people
and time to get a few more multimeters to fill those bench cavities
I do have a simple query: what's the deal with the vertical positioned DSO in the top left corner?
A measurement trick I'm not aware of, the unit has horizontal trace issues, 'space, the final frontier..'
or the owner had one too many beers ? ;D
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To me the coolest looking scope there is the red one in the middle! I didn't know that lab T&M gear came in such nice colors! :-DD
(automotive and portable certainly are part of the rainbow)
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The orange multimeter is thinking... \$\Omega\$
"just what do they hope to achieve parking my butt here amongst the big boys
...with no leads?" :-//
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This thread is amusing. For me:
Multiple multimeters: measuring so many things at once. I had 5 on a test rig the other day. One measuring input current. Two measuring output voltage. Two measuring output current. Then I needed to test a bias point on the circuit >:( ... plus they look nice all lined up like an army.
Multiple oscilloscopes: Bar the exceptional case with BravoV above with a lot of very nice newish scopes, this happens for most people when they have old analogue scopes. It starts of as an "oh I need a scope and that one is cheap". However the things are so bloody unreliable even if there are romantic aspirations about how excellent they are. So you buy one scope, fix it. Works! Woohoo. Then you find out there's a dodgy switch or the HT gives out right in the middle of something. Then you find out you can't get parts for it any more apart from some guy half way across Europe who has a stash of rare parts which cost you a kidney. So you're at a hamfest and you see another one for a reasonable price which you hope will live up to your expectations. "Yeah of course it works mate" says the guy taking your cash. Get home and it does work. Apart from one minor function you are going to need. So you then have two scopes and cannibalise one to fix the other. Then an attenuator packs in or you find it won't cal and the process starts again. After a few months you turn into me who has had 44 oscilloscopes in the last 20 years, 35 of them in the last three years. Then there's a sudden click in your mind, you sell all the damn things vowing never to touch an analogue again so you buy a Rigol because it at least mostly works. Plus you made a ton of cash selling all those scopes off to people after that hell you just went through. Life is good. For a while. Then you realise you need X-Y mode and the Rigol one sucks balls. So you look on gumtree and find a cheap analogue crate just for X-Y. Then you remember how fond you were of a user interface that isn't buried in menus. Then the analogue fear of failure kicks in and you start stuffing them on the watch list on ebay. :scared:
I haven't worked out if this is a mental illness or not yet.
Now multiple power supplies ... that's another one. I've got 4 supplies with 7 outputs and several little meanwell switchers and it's never enough.
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Cheap multimeters are so capable these days with 6000 or even higher count meters for less than $20 USD that you're crazy not to have at least 2, preferably at least 4 so you can do input and output measurement of both voltage and current simultaneously.
Get "a good one" if you want, but for the majority of people "4 cheap ones" is better than "1 good one" if you ask me.
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Problem is, you can only know what the real voltage is if you only have one meter. If you have many meters you can never be sure!
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If you have lots of good Flukes you can be sure. These two are 20 years apart. Left one cal 2018. Right one cal never!
(https://imgur.com/D1FWYqf.jpg)
Sometimes they all agree!
(https://imgur.com/uChqn9H.jpg)
>:D
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Problem is, you can only know what the real voltage is if you only have one meter. If you have many meters you can never be sure!
You can never know the "real" voltage. You can only know it to within a range. With only one meter, you know only the assumed value and the assumed nominal range. The assumption is that your meter is working and in spec. I am sure all of us at one time or an other damaged our tools before. So that assumption is an iffy one.
With two meters, you can test that assumption, make the error range shorter, as well as increase that confidence. With many meters, you can do statistical analysis to get to an even narrower range of probable error. But, you can never get to zero error.
When I was college age, I would probably say DMM's are like girl friends, the more the better. But that view would of course be very politically incorrect today...
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This thread is amusing. For me:
Multiple multimeters: measuring so many things at once. I had 5 on a test rig the other day. One measuring input current. Two measuring output voltage. Two measuring output current. Then I needed to test a bias point on the circuit >:( ... plus they look nice all lined up like an army.
Multiple oscilloscopes: Bar the exceptional case with BravoV above with a lot of very nice newish scopes, this happens for most people when they have old analogue scopes. It starts of as an "oh I need a scope and that one is cheap". However the things are so bloody unreliable even if there are romantic aspirations about how excellent they are. So you buy one scope, fix it. Works! Woohoo. Then you find out there's a dodgy switch or the HT gives out right in the middle of something. Then you find out you can't get parts for it any more apart from some guy half way across Europe who has a stash of rare parts which cost you a kidney. So you're at a hamfest and you see another one for a reasonable price which you hope will live up to your expectations. "Yeah of course it works mate" says the guy taking your cash. Get home and it does work. Apart from one minor function you are going to need. So you then have two scopes and cannibalise one to fix the other. Then an attenuator packs in or you find it won't cal and the process starts again. After a few months you turn into me who has had 44 oscilloscopes in the last 20 years, 35 of them in the last three years. Then there's a sudden click in your mind, you sell all the damn things vowing never to touch an analogue again so you buy a Rigol because it at least mostly works. Plus you made a ton of cash selling all those scopes off to people after that hell you just went through. Life is good. For a while. Then you realise you need X-Y mode and the Rigol one sucks balls. So you look on gumtree and find a cheap analogue crate just for X-Y. Then you remember how fond you were of a user interface that isn't buried in menus. Then the analogue fear of failure kicks in and you start stuffing them on the watch list on ebay. :scared:
I haven't worked out if this is a mental illness or not yet.
Now multiple power supplies ... that's another one. I've got 4 supplies with 7 outputs and several little meanwell switchers and it's never enough.
OCD affected serial naggers may call it 'hoarding' :blah: :blah:
but whatever it is, rest assured YOU ARE NOT ALONE ! :scared:
fwiw: I reckon it's the easy access of finding wish/want gear on the internet and getting it shipped asap
and yeah, having to fix gear that one needs to use to fix gear can be a pain, and easier to just get another in the meantime,
and then finding time to fix all the broken ones in one hit, source parts etc (wishful thinking on sourcing 'finding time' parts)
Then there's the trap of casual surfing on Ebay and other sites to 'see what's around' and 'what ones gear is worth to sell off' :-//
and then you spot something with low bids or no bids, local pickup..mint condition :o
and well, need I continue.. ? :-[ :palm:
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It aint hoarding if you use them tools. :-DMM
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Well id say collecting test equipment is still a better hobby than collecting most other things like stamps or baseball cards.
The resulting pile of equipment does come useful every so often even if the piece of specialty gear in question was not powered on for the last year or two. Also the process of it is pretty exiting as you celebrate a little inside every time you score a piece of gear for a great bargain price, then comes the tense wait for it to get here as you have second thoughts about how hard it might be to fix. Then the thing finally arrives, taking it apart and looking at whats in there and how it works, sometimes getting everything apart and back together is a bit of a mini puzzle. Sometimes it just needs a new fuse, other times its an adventure of tracking for the spare parts. And then it finally WORKS again and its a great sense of accomplishment. You proudly clean it to make it look as new as possible, give it any missing feet and put it up on a shelf.
There is also plenty of progression since quite a lot of times you need other gear to fix or calibrate whatever you bought so you have to gradually bootstrap yourself up the chain, giving you a nice sense of progress trough it all. And it doesn't stop once you have every major category of instrument, there is always an instrument out there with more performance than what you got, so it also becomes a matter of upgrading your gear collection to reach new heights of GHz,TOhms, nV, pA etc....
Tho if you are going for a collection of gear similar that of the TheSignalPath youtube channel then you will need some pretty deep pockets.