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MARTIN LORTON: Hello, YouTubers, and welcome to this Quick Tech video; where we're going to have a look
at the pros and cons of analog versus digital multimeters
In this comparison, we're going to have the Fluke 87 series
5 versus the Mastec M7040
Now, the reason I've selected the Fluke is because it does have a fairly nice
update speed on the digital display and a really nice
fast, bar graph. So, it makes a fair comparison against something like an analog meter
because a digital meter uses a bar graph to try and
get as close to the needle on an analog multimeter. Many other, digital
multimeters attempt to do this with their bar graphs but
they're often very slow and jumpy, and come nowhere close to trying to represent
an analog needle or analog representation of a voltage.
Now, one of the first advantages to be noted with a digital meter versus an
analog one is the robustness because an analog meter has
a needle and a coil to represent its reading
it can be very sensitive and delicate to vibrational harsh
shocks. So, where as most digital multimeters can take a fair
knock, and some are rated for being dropped from fairly high heights without any issue
An analog meter, if it is dropped or vibrated very hard will
either go out of calibration or it will actually damage the analog needle
and the actual unit itself. These can, however, be put in boxes
or cases. This one does have a protective, rubber case around it.
and if it was put in a case with some, shock-absorbant sponge and a good
cover, that certainly would alleviate that issue to some extent.
The next, obvious challenge between these two meters is actually taking a reading
from each of their displays. We've obviously got a digital representation here
and an analog via this needle on the analog meter.
Now, if I switch on my power supply, it will be interesting to see how quickly you can guess
what the actual reading is, and then we'll go through the challenges on both meters.
So, as I switch that on, you'll see that the needle
swings up to a value, but quite clearly you can quickly take
a fairly quick and accurate reading off the digital meter. 7.09 volts.
Once we get to the analog meter, there are a few challenges
that we have to overcome. However, I'm going to show you a demonstration a little
later which will clearly show the advantages of having a needle display
a reading versus a digital read out. One of the first challenges you have
to overcome with the analog meter is that you have to select your range. Now
this might be the case for some digital meters which aren't auto-ranging
but for all analog meters, you're going to have to select the range ahead of time
and make sure you do it correctly
If you select a scale that is too sensitive, so if I went down to have this on 10 volts
and I was measuring 100 volts, I would have a huge
deflection on the needle and potentially damage the workings of the needle
and the internal protection of this meter might not cater for that. That's something
we're going to have a look at in later videos in comparison with digital meters
Once you've got your scale selected correctly, we then have to
decipher what's happening with the actual needle. In this
case, we need to understand there are several scales for
either measuring resistance, DC volts and current,
AC volts, and then even micro-amps, milli-amps
and logarithmic displays as well. So, we first of all
we must decide which scale we're on. In this case, it's this bottom scale
over here. We've got it set to the 10 volt scale
so on the meter over here, we can see we've got a 250
a 50 and a 10 scale for DC voltage
We then have to go and say, right, we are now
between the six and the eight on the scale up here
So, that means we're on about seven. The other challenge you need to deal with
when trying to get an accurate reading off of your analog meter
is that the needle is offset from the actual scale itself
and you can get something called an "error of parallax" Where you're looking down at the
meter at an angle and you're not lining the needle up
with the actual graduation on the actual scale itself. What some meters have
to try and compensate for that and help you, is this little, silvered
or mirrored scale at the back. And what you need to do is
close one eye and line up like a gun sight
the needle with it's reflection in the actual mirrored part
of the scale to make sure that you're looking at the actual graduation
correctly. So, that's certainly on disadvantage where you certainly
going to get a reading straight off from your digital multimeter.
Cerftainly, one of the most obvious challenges as well is that, although this is analog
and, in theory, can give you a higher resolution on your
reading, that can be very difficult to accurately read
off a fine reading on these graduations. Whereas
a digital multimeter can give you readings down to several decimal places
which are quick and easy to read off, and you're not going to get that kind of resolution
on an analog multimeter. Accuracy can also be a
challenge. Once you're switching between the ranges, I've certainly found
on some analog meters, that it will be accurate on some of the ranges but then
slightly out on others. That may differ between the more
expensive meters. You do have a little adjustment screw over here
once you've made an adjustment for one scale, you might find
you're slightly out on another scale. I'm going to demonstrate one example where
an analog meter and the needle position may hold an advantage
against trying to understand or decipher what's on a digital display. We've got a situation where, let's say
you're on site and you've got multiple devices and you've got to pick up
test points on multiple devices and check that they have the same reading
You might not have the meter immediately in front of you, it might be off to the side
while you're trying to probe these devices in a cupboard. So, let's say we're trying to
look for a test voltage of 1.5 volts. If I just simply
plug in to my power supply right now, you'll see that we've got the 1.5 displayed
on the digital display and on the analog display, we have to
use a top scale, which is showing 150, which we have to divide by 100
to get the reading, but once we are familiar with
the position of the needle, if we are doing multiple tests, it might be easier
to decipher. So, let's pull out. I go to the next device, plug
in. Pull out,
go to the next device, and plug in. If I'm off to the side,
it might be easier just to quickly note the position of the needle, rather than
digits which are jumping around on a digital display. This will vary
from situation to situation and, in some cases obviously, the digital meter will have an advantage
but there are certainly some cases where a quick reference and look-up
of the position of the needle on an analog meter is far easier to decipher
than trying to understand what is happening with the changing digits on a digital display.
This certainly becomes more apparent when you have a fluctuating signal
Now, if this signal is not fluctuating too much, the Fluke
copes not too badly because it's got a nice representation on its bar
graph at the bottom of the display. As you can see, what they're trying to do
is indicate that you have got some fluctuation and try and emulate what the needle is doing
on an analog multimeter. I'm now going to switch from the signal generator. Which is
going to generate a pulse every two seconds, which goes somewhere between about
three and a half, close to four volts and up to just over six volts
This could be a simulation of, let's say,
an intimate connection on a piece of wire or a signal coming through
on some piece of electronics. If you look at the displays, it's very difficult to
try and pick up and understand, even with the bar graph in this case,
what's going on on a digital multimeter. You've got two problems here. You
have got the digits which need to settle and you brain needs to understand what they represent
and it's going through an auto range and having to stop and think
and autorange to try and settle on the correct range and therefore
the display is just jumping around. Whereas on the analog display
it's far easier to see that we've got something varying between these two values
and a little closer look will show us that we're going between just below four
volt and just over six volts on the display.
This can be overcome to some extent on a digital meter once we go into a manual range
So, if I select the correct manual range, we see
then we get a little deflection on the actual bar graph on the bottom which shows us we've got
a deflecting voltage and then we do get the display
just about showing us what the two voltages are, but none of this
the brain has to stop and compute what the digits are displaying and, as I said, for some
folks that may be natural, for other folks, you may find it's far
easier to pick up what the analog needle is showing rather than that changing
digital display. Again, another example of where an analog needle
may give you a far easier understanding of what a reading is doing
versus a digital display is, let's say if you're measuring sensors.
Let's say we take a temperature sensor. Let's say we need to quickly react to
a rising temperature sensor or whether it's dropping in temperature
If we have a look at this and we've got the reading displayed on these two meters
If we need to take an action with, let's say, the temperature going up, all you have to note,
on the analog display, is a movement
one of two movements. Whereas, often on a digital display, you're going
to have the jumping figures and your mind is going to have to compute
is that number increasing or decreasing? So, it's far easier to decipher
that the temperature is going up just because you're noting
the movement of the needle and you've got a far great, wider view
in effect of what's going on, rather than this narrow view changing
digits. Next, we'll have a look at measuring resistance
Now, on your analog meter again, the one thing you need to do is set the appropriate range
first off. In this case, we're going to check
a resistor that has a measurement of 60 ohms.
Now, if I go and put my probes straight on the actual resistor and do a measurement
if we have a look at the way the needle works, it actually
starts off at infinity and moves down to our
zero ohm mark. So, that's the one thing we note. As opposed to an increasing value
we've got a decreasing value
When I put the probes on the resistor, we'll see that this is representing somewhere around
70 odd ohm. So, what's the problem?
On an analog meter, because you've got a battery driving the
measurement and several ranges which use the same scale
you need to calibrate the meter each time you take a resistance reading.
Now, this meter happens to have a continuity tester, so with the low
test, you're going to get a buzz while I calibrate the actual probes
There's a dial here, so I can calibrate it to zero
*prolonged beep*
So, there you go, it's calibrated to zero, and now I'm ready to take the measurement
If you've got your eye correctly
lined up on the needle, you'd see that it's got a reading of about 60 ohm on
the display
Next, I'm going to test a resistor which is 6000 ohm or 6 K
I've gone and changed the actual setting on the selector over here to times
100 for the scale
and again, if we look at that, it is showing us something around
5 K. So, what didn't I do? Again
as I said, when you change your selection range, you have to put your leads together
Zero the display and then you're ready to go and take your
reading. Now, the one advantage of that is that you're always
calibrating for losses in your leads but it does become a hassle in that you need to calibrate
every time you change your range to make sure you get your reading correct.
And, there we go again, if you line up your eye correctly, we're now reading 6 K.
The obvious point there is that trying to show an accurate or the resolution
on an analog scope can be a challenge
Especially once we get up to a higher scale. On the lower scale, you can see your graduations go
from zero, one, two, five, ten. So, you've got a reasonable
amount of resolution and range there for your final resistance levels
but certainly not to any great accuracy or resolution
Once we start getting to these higher readings, you're going to have a large
change in resistance for small movement on the needle because you just don't have the
resolution. So, again, if I'm taking this and trying
to understand exactly what that is, I would know that it's around
6 K. Where if I go to the digital meter
it pops up straight away and I can see we're at
6.07 K which is certainly something I wouldn't be able to see
on the analog meter. Right, so those are probably some of the key
differences and things to be aware of analog versus digital meters
but I'm sure I've gone and missed some. I'm sure some folks out there
that have been using analog meters for a long time and have come up against some other challenges or
or advantages of using an analog meter versus a digital
If that's the case, certainly, please post your comment below. And of course, in today's world
the digital meters, even the cheaper ones, have a lot more functionality
whether they can record things like min-max average, to data logging
have an auto hold facility. So, there are many advantages to
going digital, but nonetheless the analog world still has something
to show. Anyway, thanks very much for watching, and I'll catch you soon for the next video.
Cheers.
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