EEVblog #1067 - Analog vs Digital Multimeters

[glarsson]

Car speedos and aircraft instrumentation are designed so a pilot or driver can take a quick glance and roughly see if everything is ok or not.

Agreed for aircraft. For cars you do not need the speedometer to get a rough measurement of your speed.  Just look out throug the windshield!

[Fungus]

For my hobby I have a 100k, 60k and 10k DMM, but in my boat I still have this 60 year old AMM from my dad which is perfect there:
- Never empty battery (biggest advantage for a meter hardly used)
- Excellent to see if there's a voltage or if the battery is full or empty

It is so convenient if you just need basic functions and no precision 

Amazingly enough: You can power a digital meter from the boat battery itself, no need for a separate battery to power it!

If your analog meter falls in the sea, will you go looking for another old meter or will you install one of these for $2?

[Fungus]

Car speedos and aircraft instrumentation are designed so a pilot or driver can take a quick glance and roughly see if everything is ok or not.

Agreed for aircraft. For cars you do not need the speedometer to get a rough measurement of your speed.  Just look out throug the windshield!

The same thing could be said for aircraft.

Look out of the window: Are the houses getting bigger when they shouldn't be? Yes: Increase engine power.

[glarsson]

No. Clouds, darkness, fog, etc make it impossible to judge speed correctly. You can still safely fly an aircraft if instruments are used. The same can not be said about a car.

[mdijkens]

For my hobby I have a 100k, 60k and 10k DMM, but in my boat I still have this 60 year old AMM from my dad which is perfect there:
- Never empty battery (biggest advantage for a meter hardly used)
- Excellent to see if there's a voltage or if the battery is full or empty

It is so convenient if you just need basic functions and no precision 

Amazingly enough: You can power a digital meter from the boat battery itself, no need for a separate battery to power it!

If your analog meter falls in the sea, will you go looking for another old meter or will you install one of these for $2?

Of course I have a power monitor in my boat that monitors both batteries voltage, capacity, wear and in-/outgoing amps.
But that doesn't help you much if you need to fix something. If something doesn't work anymore you want to be able to figure out where the problem is

[Fungus]

But that doesn't help you much if you need to fix something. If something doesn't work anymore you want to be able to figure out where the problem is

Right, but you could use one of those to look at voltages. It meets your requirements of "never empty battery" and "Excellent to see if the battery is full or empty".

You could even put it in a box and attach a couple of multimeter probes if you want it to look pretty and/or be waterproof.

[Kleinstein]

Analog meters are obsolete. Period.

So is my old 486 computer running Windows 3.11 - but I still can't type faster than it can handle.
...

A newer computer / OS might help here. With Windows 8.1 you can sometimes be faster 


Back on Topic:
The bar graph display just flickering on the last segment as Dave showed is not a reliable response. This can also happen just at the boundary. So even of the needle movement is just visible this is still more useful than just one segment flickering.  So in this respect many of the digital meters still don't work that well, because the bar graph resolution is too limited.

[Cnoob]

Car speedos and aircraft instrumentation are designed so a pilot or driver can take a quick glance and roughly see if everything is ok or not.

Agreed for aircraft. For cars you do not need the speedometer to get a rough measurement of your speed.  Just look out throug the windshield!

So you don't take a quick glance at the speedometer when you need to reduce speed to obey a speed limit!
It is also illegal not to have a working speedometer in your car if your car is newer than 1935ish(uk law.) 

[glarsson]

When I look at the speedometer the goal is not to get the answer "about 30km/h". The goal is to get an answer that can be used to decide if any speed correction is required. The answer 30 is acceptable and 32 will require correction. For this the analog speedometer is not the best option. The calibrated digital readout is what I use.

Don't know what UK rules about working speedometers have to do with this question.

[Cnoob]

You have answered it. You need a working speedometer to make speed corrections.

Originally I was stating  you can not liken an analogue speedometer to a  multimeter.

[glarsson]

I never argued that the speedometer should be removed, broken or something similar. End.

[vk6zgo]

Analog multimeters are not safe at all, never use them on high energy circuits.....

What do you imagine we used before DMMs?

The AVO 8 & the like were very well engineered, with large clearances, heavy insulation, & thick Bakelite cases.
Because they were large, meters of this class were not used handheld.
Instead, they were placed on the floor, rested on a "Tech's stool", or hung up by the handle.

In any case, the operator could be a metre or more away from the meter & still read it clearly, which reduced the possibility of injury in the very unlikely event of the meter case being breached.

In more than 40 years working at high power Radio & TV transmitter sites, I only saw one AVO 8 which had been "blown up".
The Bakelite case was not breached, the movement was clearly charred, the dial glass was cracked, but not
shattered.

DMMs are mostly used handheld, & have lightweight cases, so your chances of escaping injury are that much less.

I think you do not know at all the subtleties, or especially the weaknesses of the Avo 8  .....

An unbiased observer might  think that using the things every day, for decades, often in "high energy" circuits would give me a pretty good handle on its subtleties.

First of all, I learned to drive with my father's Simca Aronde: this car had no seatbelts, no airbags, no ABS and was not crash tested ... and yet, everyone was driving with such insecure cars.

Safety standards have changed and it would be forbidden to drive today with such a car.

In most Countries it is not, & you can still drive such old vehicles.
In any case, none of those things, except perhaps ABS adds one bit to the primary safety of the car, but only come into play if the driver does not avoid a perilous situation.

With regard to electrical safety, it's the same thing.

So to argue that we used in the past analog multimeters on high energy circuits, it's simplisly stupid.

You can't ignore actual safety rules.....

As I pointed out, the AVO was inherently safer because of very heavy construction & proper engineering, whereas DMMs are handheld devices with quite flimsy construction.
CAT ratings were introduced after the introduction of DMMs.
"Safety rules" are more to do with how the testing is done, rather than the rating of the testing device.

The avo 8 is very dangerous because it is the same terminals that are used for both the voltmeter and ammeter function .... an error can easily be made.
 

Many thousands of these instruments were used over decades without injury, mainly because the people using them followed correct safe operating procedure.

In addition, the so-called cutout protection does not protect anything because:

1) the breaking capacity of this cutout is very low
2) the protection is activated by the needle arriving at the end of scale stop ..... but if you are in range DC amps and you measure AC current, the needle does not move at all and does not cause the opening of the cut out.

Then, the principle that there is no danger because we do not hold the meter in hands is totally wrong and shows that you do not know anything about electrical safety.

So now I'm both stupid & know nothing?
Like all those thousands of other Techs, EEs, & Electricians that used AVO 8 meters?
Do you often have these feelings of superiority?

In a high energy circuit, the risk comes from creating an arc that becomes explosive.

This arc is formed at the contacts, that is to say the test probes held by the operator and ionised air let the arc to close between phases with consequences of serious burns, damage to the eyes and a risk of electrocution.

In most cases, it is possible to clip the probes in place & not have to "hold them".
OK, perhaps in the high energy circuits we tested it was usually possible to isolate the incoming Mains, connect the meter, then re-apply the power.

With high energy circuits, every simple error have very serious consequences and it is not for nothing that the digital multimeters have special fuses with high breaking capacity in the current inputs.

The trick, (which isn't that hard), is  to not make "simple errors").

[Cnoob]

I never argued that the speedometer should be removed, broken or something similar. End.

Car speedos and aircraft instrumentation are designed so a pilot or driver can take a quick glance and roughly see if everything is ok or not.

Agreed for aircraft. For cars you do not need the speedometer to get a rough measurement of your speed.  Just look out throug the windshield!

You implied you did not need a speedometer.

[glarsson]

No. I wrote that to get a rough estimate of the speed you just look outside the window, something you are supposed to do anyhow (uber drivers excepted). If you need a more exact speed you obviously look at the speedometer. The argument was that the speedometer on a car doesn't have to be designed to give quick rough estimates compared to an environment where no other means to determine speed might not be available, such in an aircraft under certain conditions.

[Harb]

How boring would a lab be with only digital test gear.........each has its place in my Lab, and I will never agree with anyone trying to tell me Digital meters are better/faster for Nulling or Peaking anything.

[oldway]

Analog multimeters are not safe at all, never use them on high energy circuits.....

What do you imagine we used before DMMs?

The AVO 8 & the like were very well engineered, with large clearances, heavy insulation, & thick Bakelite cases.
Because they were large, meters of this class were not used handheld.
Instead, they were placed on the floor, rested on a "Tech's stool", or hung up by the handle.

In any case, the operator could be a metre or more away from the meter & still read it clearly, which reduced the possibility of injury in the very unlikely event of the meter case being breached.

In more than 40 years working at high power Radio & TV transmitter sites, I only saw one AVO 8 which had been "blown up".
The Bakelite case was not breached, the movement was clearly charred, the dial glass was cracked, but not
shattered.

DMMs are mostly used handheld, & have lightweight cases, so your chances of escaping injury are that much less.

I think you do not know at all the subtleties, or especially the weaknesses of the Avo 8  .....

An unbiased observer might  think that using the things every day, for decades, often in "high energy" circuits would give me a pretty good handle on its subtleties.

First of all, I learned to drive with my father's Simca Aronde: this car had no seatbelts, no airbags, no ABS and was not crash tested ... and yet, everyone was driving with such insecure cars.

Safety standards have changed and it would be forbidden to drive today with such a car.

In most Countries it is not, & you can still drive such old vehicles.
In any case, none of those things, except perhaps ABS adds one bit to the primary safety of the car, but only come into play if the driver does not avoid a perilous situation.

With regard to electrical safety, it's the same thing.

So to argue that we used in the past analog multimeters on high energy circuits, it's simplisly stupid.

You can't ignore actual safety rules.....

As I pointed out, the AVO was inherently safer because of very heavy construction & proper engineering, whereas DMMs are handheld devices with quite flimsy construction.
CAT ratings were introduced after the introduction of DMMs.
"Safety rules" are more to do with how the testing is done, rather than the rating of the testing device.

The avo 8 is very dangerous because it is the same terminals that are used for both the voltmeter and ammeter function .... an error can easily be made.
 

Many thousands of these instruments were used over decades without injury, mainly because the people using them followed correct safe operating procedure.

In addition, the so-called cutout protection does not protect anything because:

1) the breaking capacity of this cutout is very low
2) the protection is activated by the needle arriving at the end of scale stop ..... but if you are in range DC amps and you measure AC current, the needle does not move at all and does not cause the opening of the cut out.

Then, the principle that there is no danger because we do not hold the meter in hands is totally wrong and shows that you do not know anything about electrical safety.

So now I'm both stupid & know nothing?
Like all those thousands of other Techs, EEs, & Electricians that used AVO 8 meters?
Do you often have these feelings of superiority?

In a high energy circuit, the risk comes from creating an arc that becomes explosive.

This arc is formed at the contacts, that is to say the test probes held by the operator and ionised air let the arc to close between phases with consequences of serious burns, damage to the eyes and a risk of electrocution.

In most cases, it is possible to clip the probes in place & not have to "hold them".
OK, perhaps in the high energy circuits we tested it was usually possible to isolate the incoming Mains, connect the meter, then re-apply the power.

With high energy circuits, every simple error have very serious consequences and it is not for nothing that the digital multimeters have special fuses with high breaking capacity in the current inputs.

The trick, (which isn't that hard), is  to not make "simple errors").

When it comes to safety, you do what you want, you are the only one responsible for your life.

By cons, on this forum, you are in a public space and it is not acceptable that you publicly give advice contrary to safety.

[Fungus]

Analog multimeters are not safe at all, never use them on high energy circuits.....

What do you imagine we used before DMMs?

You used what was available, obviously.

That didn't make it safe though. 

[Cnoob]

No. I wrote that to get a rough estimate of the speed you just look outside the window, something you are supposed to do anyhow (uber drivers excepted). If you need a more exact speed you obviously look at the speedometer. The argument was that the speedometer on a car doesn't have to be designed to give quick rough estimates compared to an environment where no other means to determine speed might not be available, such in an aircraft under certain conditions.

I stated the opposite that a analogue speedometer is a speed indicator as opposed to a measment device. Also I did not make  a direct reference  to air speed indicators. I refered to aircraft instrumentation. In fact I was thinking  of engine services. Reason why I mentioned paint bars around the dials.

[TJM]

Quite funny is that almost everyone assumes analog multimeter always has low input impedance. I've just checked the specs on my old Meratronik V640 which I used for years (those were extremely popular here in Poland and lots of them are still in use even today) and at DC volts it is rated at 100M on all ranges (1.5/5/15/50/150/500mV/1.5/5/15/50/150/500/1500V)  while on AC volts its rated at 10M below 150mV and 100M from 500mV range up to 1,5kV.

I've used quite a few analog meters in the past (I got my first DMM in very late 90's and it was extremely expensive, also complete garbage compared to the V640) and even an old Russian meter I bought as 10years old kid used some weird custom hybrid IC as the input stage to get at least 10MOhm input impedance on low ranges.

[akimmet]

The only time anymore I use an analog meter is when troubleshooting automotive wiring. Cheap DMMs do a poor job of displaying intermittent connections. A quality meter can do a good job of it, but only if you remember to disable auto ranging. That can be frustrating to forget when you are underneath a vehicle. However, for this purpose I suppose a 12V test lamp is probably a better tool for the job.

There is a small unintended benefit to using an analog meter outside, no one is interested in stealing it. The same can't be said about even those cheap free harbor freight DMMs.

[tzok]

In Poland we have one analog multimeter which gained a status of a legend. It's a MeraTronik V640 (known for the Western Bloc as a Conway model 639 and Marconi TF-2650 FET Multimeter). For sure, there were better multimeters at that time ('70s and '80s), but not in the Eastern Bloc. What may still impress in it is the 100M\$\Omega\$ input resistance (full range DC, and AC from 500mV range), 1500uV range,  and capability of measuring AC signals of up to 100kHz without a HF probe (according to manual the range was to 20kHz, but in practice it was much more), 100M\$\Omega\$ ohmmeter range (half-scale, so 10G\$\Omega\$ full-scale).

@oldway - when it comes to the safety, my opinion is that awareness of danger is more important that safety of the device itself. The more the device is "safe", the less cautious operator is. So I don't really like the government/companies think "for me". Then I don't like saying "you should never use it", I'd rather say "you should be cautious while using it". When it comes to the cars - you may still drive a car form '20s if you like. Old cars (mostly with 2-stroke engines) were only banned in some big cities for the emission standards. Some cars were banned due to safety reasons from sale, but it happened when they were in-production.

[vk6zgo]

Analog multimeters are not safe at all, never use them on high energy circuits.....

What do you imagine we used before DMMs?

You used what was available, obviously.

That didn't make it safe though. 

No, but adherence to safe usage rules did!

[vk6zgo]

By cons, on this forum, you are in a public space and it is not acceptable that you publicly give advice contrary to safety.

If you had said :-

" I do not recommend analog multimeters for use on high energy circuits.
They were used safely in the past by qualified people using rigorous precautions, but because they do not include the protective systems used in modern DMMs, they are not suitable for untrained people".

I would have passed, & not replied.

Instead, you wrote:-

"Analog multimeters are not safe at all, never use them on high energy circuits..... "

A blanket statement,  which although it may be intended to protect  beginners. is patently untrue.

You then go on to introduce "red herrings" about cars,etc.
Later, you posted the following:-

The avo 8 is very dangerous because it is the same terminals that are used for both the voltmeter and ammeter function .... an error can easily be made.
 

Standard procedure with the AVO 8 is to  set the "DC ranges" switch to"AC, & the " AC & Ohms switch" to "DC",  prior to use, & only then, set the required mode & range.

Even if I conceded your point about the AVO 8, it really only applies to that instrument, as not all analog multimeters use the same terminals-----I have seen, & used an analog meter which not only had separate "Amps" terminals, but had a mechanical interlock to prevent setting it to a  voltage setting if there were leads attached to those terminals.
I can't remember who made it-----maybe Metrix?

In addition, the so-called cutout protection does not protect anything because:

1) the breaking capacity of this cutout is very low
2) the protection is activated by the needle arriving at the end of scale stop ..... but if you are in range DC amps and you measure AC current, the needle does not move at all and does not cause the opening of the cut out.

As far as I remember, without a manual in front of me, the cutout is just there to protect the movement,  just as other meters use diodes.

[Brumby]

when it comes to the safety, my opinion is that awareness of danger is more important that safety of the device itself. The more the device is "safe", the less cautious operator is.

Yep.

[oldway]

There is no choice to do between safety of the multimeter, awareness of danger and user attention, all are equally important.

Accidents happen, even with the most cautious people .... that's true in all areas, not just the measurement on high-energy circuits.

As long as measurements are made on low energy circuits, for example 220V protected by a 25A circuit breaker, the consequences of an error remain limited.

On the other hand, when it comes to 400V with a 630A circuit breaker, the situation is a little different.

I bought an AVO 8 mark IV in the 70s, I still have another AVO8 mark IV at home right now, I'm very careful and yet I have made mistakes in its use.

Contrary to what is stated, it is very easy to be wrong in the selection of ranges.

With power electronics and electrical measurement  in high energy circuits, you simply CAN'T use a multimeter that uses the same inputs for voltages and currents.

In safety, rules are mandatory....If you don't know this, you know nothing about safety.....