alan8376
Well-Known Member
A question for the 'techies?' Which is best for boat electrical work, where damage to circuits could be caused by use of wrong type?
Thanks
Thanks
Multimeter. Analogue or Digital?
- Thread starter alan8376
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mortehoe
Well-Known Member
What damage and why?
Can you still buy analog meters???? Go digital - Even the off-the-shelf-bog-standard cheapo ones are all smt cmos.
I don't understand your comment that circuits could be damaged by using "the wrong type" of multi-meter.
Can you still buy analog meters???? Go digital - Even the off-the-shelf-bog-standard cheapo ones are all smt cmos.
I don't understand your comment that circuits could be damaged by using "the wrong type" of multi-meter.
alan8376
Well-Known Member
Re: What damage and why?
Maybe I mis-heard the info! From my car knowledge. I believe digital is the only way of measuring the very low voltage used in some circuits. Does this apply on modern boats?
Maybe I mis-heard the info! From my car knowledge. I believe digital is the only way of measuring the very low voltage used in some circuits. Does this apply on modern boats?
Poignard
Well-Known Member
Re: What damage and why?
[ QUOTE ]
Can you still buy analog meters????
[/ QUOTE ]
Well - it just so happens that I have an Avo 8x with leads that I would like to sell, if anyone's interested!
[ QUOTE ]
Can you still buy analog meters????
[/ QUOTE ]
Well - it just so happens that I have an Avo 8x with leads that I would like to sell, if anyone's interested!
Fr J Hackett
Well-Known Member
If you were doing real diagnostic work you would know and understand that an anologue meter is what you should be using, if however you are simple 12 volt is it there or not cicuit testing a digital is perfectly acceptable. A anologue meter such as the excelent but bulky AVO is quite expensive and best not left on the boat but for a few quid you can purchase a cheap digital from Maplin or RS etc and leave it on the boat. Buy a digital.
nedmin
Well-Known Member
Re: What damage and why?
A good reasonably priced digital is better than a reasonably priced analogue,you should get something decent for about £30. I still like analogue for testing for continuity and voltages but not if you want really accurate readings,unless you have something like an AVO8.but how often do we need to go to 1/10 of a volt?
A good reasonably priced digital is better than a reasonably priced analogue,you should get something decent for about £30. I still like analogue for testing for continuity and voltages but not if you want really accurate readings,unless you have something like an AVO8.but how often do we need to go to 1/10 of a volt?
Stemar
Well-Known Member
Re: What damage and why?
I may be wrong, but I think that the only way a test meter could damage electronics is if you're doing insulation testing using a high voltage. Meters that do this are professional jobs that cost an arm and a leg.
You might, just possibly, be able to damage components by poking around inside electronics on the ohms setting, but I doubt it.
Nearly forgot - one sure way to break things is to cause a short circuit with the leads - you don't even need a meter attached!!
IMHO, if you need to ask the question, a cheap digital job should be fine for you. Mine cost less than a fiver from Maplin
I may be wrong, but I think that the only way a test meter could damage electronics is if you're doing insulation testing using a high voltage. Meters that do this are professional jobs that cost an arm and a leg.
You might, just possibly, be able to damage components by poking around inside electronics on the ohms setting, but I doubt it.
Nearly forgot - one sure way to break things is to cause a short circuit with the leads - you don't even need a meter attached!!
IMHO, if you need to ask the question, a cheap digital job should be fine for you. Mine cost less than a fiver from Maplin
elton
Well-Known Member
Re: What damage and why?
You can damage electronics with either a digital or an analogue meter if you try to measure voltages with the meter set to measure current.
You can damage electronics with either a digital or an analogue meter if you try to measure voltages with the meter set to measure current.
cliff
Well-Known Member
Re: What damage and why?
Don't you mean you can damage electronics with either a digital or an analogue meter if you try to measure voltages with the meter set to measure current or resistance.
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Don't you mean you can damage electronics with either a digital or an analogue meter if you try to measure voltages with the meter set to measure current or resistance.
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sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>
elton
Well-Known Member
Re: What damage and why?
Both. Trying to measure current or voltage with the meter set to measure resistance can damage the meter and/or the the equipment (the meter applies a voltage to the test leads and measures the current, in order to measure resistance). It depends on what you're testing and which way round the leads are.
Trying to measure voltage with the meter set to measure current will almost always cause disaster. The meter is essentially a short circuit when measuring current. The best that will happen is that the fuse in the meter will blow.
Also, if you try to measure AC voltage with an analogue meter set to read DC voltage, the meter will read zero. Until you select the low voltage scales because you don't believe what it's telling you. Then the meter starts to heat up and melt as the mechanism of the meter tries to oscillate back and forth past zero 50 times a second.
Both. Trying to measure current or voltage with the meter set to measure resistance can damage the meter and/or the the equipment (the meter applies a voltage to the test leads and measures the current, in order to measure resistance). It depends on what you're testing and which way round the leads are.
Trying to measure voltage with the meter set to measure current will almost always cause disaster. The meter is essentially a short circuit when measuring current. The best that will happen is that the fuse in the meter will blow.
Also, if you try to measure AC voltage with an analogue meter set to read DC voltage, the meter will read zero. Until you select the low voltage scales because you don't believe what it's telling you. Then the meter starts to heat up and melt as the mechanism of the meter tries to oscillate back and forth past zero 50 times a second.
VicS
Well-Known Member
An inexpensive digital meter will be quite adequate. Maplin do them from as little as £5. At that price you can afford to keep one on the boat and one at home and also not shed too many tears when you bugger one up. They do an analogue meter for about £10 and a dual scale one for about £30. The £5 digital one appears to be identical to those priced double that in DIY stores
There may be uses for which an analogue meter is preferable but I can't think of any off hand. For modern electronic circuits where current flow is very small a high impedance digital meter is more likely to be required.
The high precision of digital meters (0.01v in 20v for example) is an attractive, at least seductive, feature but you should not be misled into believing that their accuracy, at least of the cheap ones, matches that. Mine are only ± 0.5% on the DC volts ranges (ie only 0.1v in 20v)
At the risk of sounding arrogant and patronising I suggest that if you have to ask this sort of question on this forum it will not matter a jot what type you have and that the cheaper (within reason) the better as sooner or latter you will blow all the shunts. I have done that with two cheap analogues and a digital AVO that I thought was adequately protected. I promise you that sooner or later you will do the same!
The last decent analogue meter that I had did not like being carted around in the car all the time so I suggest that a digital meter with no delicate moving parts would be a more suitable choice for permanent life afloat. If you do buy an analogue one be sure that the movement is damped when switched off and that you do always switch it to the off position after use. Analogue meters do have the advantage of not requiring a battery, except for the resistance and continuity ranges of course
Maplin also offer a book called "Getting the Most From Your Multimeter". It explains the differences between digital an analogue meters and discusses their relative merits. It also describes the methods for checking components and circuits. At only £5 is could well be worth buying.
There is a lot of useful info for the would be boat electrician on the TB training website but it is no substitute for a good book on the subject. There are a range of such books but "The 12 Volt Bible for Boats" is the one frequently recommended by users of this forum. It is priced around £15.
To sum up my advice would be to buy a £5 digital meter from Maplin, but watch out for special offers as I got 2 for the price of one. If you latter decide you need something more expensive buy what you need if and when you need it. The little cheapie will always come in handy.
There may be uses for which an analogue meter is preferable but I can't think of any off hand. For modern electronic circuits where current flow is very small a high impedance digital meter is more likely to be required.
The high precision of digital meters (0.01v in 20v for example) is an attractive, at least seductive, feature but you should not be misled into believing that their accuracy, at least of the cheap ones, matches that. Mine are only ± 0.5% on the DC volts ranges (ie only 0.1v in 20v)
At the risk of sounding arrogant and patronising I suggest that if you have to ask this sort of question on this forum it will not matter a jot what type you have and that the cheaper (within reason) the better as sooner or latter you will blow all the shunts. I have done that with two cheap analogues and a digital AVO that I thought was adequately protected. I promise you that sooner or later you will do the same!
The last decent analogue meter that I had did not like being carted around in the car all the time so I suggest that a digital meter with no delicate moving parts would be a more suitable choice for permanent life afloat. If you do buy an analogue one be sure that the movement is damped when switched off and that you do always switch it to the off position after use. Analogue meters do have the advantage of not requiring a battery, except for the resistance and continuity ranges of course
Maplin also offer a book called "Getting the Most From Your Multimeter". It explains the differences between digital an analogue meters and discusses their relative merits. It also describes the methods for checking components and circuits. At only £5 is could well be worth buying.
There is a lot of useful info for the would be boat electrician on the TB training website but it is no substitute for a good book on the subject. There are a range of such books but "The 12 Volt Bible for Boats" is the one frequently recommended by users of this forum. It is priced around £15.
To sum up my advice would be to buy a £5 digital meter from Maplin, but watch out for special offers as I got 2 for the price of one. If you latter decide you need something more expensive buy what you need if and when you need it. The little cheapie will always come in handy.
Sixpence
Well-Known Member
Re: What damage and why?
PM sent
PM sent
guernseyman
Well-Known Member
Re: What damage and why?
May I differ and say that an analogue meter is preferable?
The battery is likely to be type 'AA', a type likely to be carried as spares for other purposes, rather than some obscure button type.
The reading is less likely to be mistaken. I've not yet come across a need for greater accuracy. A reading is easier if it is not steady.
The little digital ones that I have owned need switching off, else you have a flat battery when you come to use it. That's not a good feature.
May I differ and say that an analogue meter is preferable?
The battery is likely to be type 'AA', a type likely to be carried as spares for other purposes, rather than some obscure button type.
The reading is less likely to be mistaken. I've not yet come across a need for greater accuracy. A reading is easier if it is not steady.
The little digital ones that I have owned need switching off, else you have a flat battery when you come to use it. That's not a good feature.
peteandthira
Well-Known Member
Re: What damage and why?
I have found an idiot proof one. You have to plug the leads into different holes to measure current, and those holes only open when the meter range knob is turned to "current". Having gone to all that trouble, I think you are less likely then to try to measure a voltage with it.
I have found an idiot proof one. You have to plug the leads into different holes to measure current, and those holes only open when the meter range knob is turned to "current". Having gone to all that trouble, I think you are less likely then to try to measure a voltage with it.
G
Guest
Guest
I have a thin small digital that slips into a wallet and then top pocket ... stays in toolbox ... about a fiver at Maplins ...
I have small analogue meters ... about size of a ciggy packet ........
I have larger Digital meters ...
At end of day I found only two things mattered for me ! >
a) LCD displays do not like below 0C ... switch on and nothing on display - if its been left out in sheds toolbox in winter !! Takes a few minutes to warm up and show !! Analogue didn't care.
b) Digitals would show high voltage even if it was barely mA ... so a "dry-joint" unless real bad didn't show .... (doing mast connections !! 12V at socket ... but no light ... 12V was so weak it was ................. ) My analogue for some reason did show less voltage indicating a problem.
But for ease of use ... and readability - Digital.
Oh I have a complaint ... why do they use tiny symbols on them instead of AC ..... DC ..... etc. ? Unless you have a magnifying glass on some - you can't tell what they are !! Yes my eyes are getting worse ....
I have small analogue meters ... about size of a ciggy packet ........
I have larger Digital meters ...
At end of day I found only two things mattered for me ! >
a) LCD displays do not like below 0C ... switch on and nothing on display - if its been left out in sheds toolbox in winter !! Takes a few minutes to warm up and show !! Analogue didn't care.
b) Digitals would show high voltage even if it was barely mA ... so a "dry-joint" unless real bad didn't show .... (doing mast connections !! 12V at socket ... but no light ... 12V was so weak it was ................. ) My analogue for some reason did show less voltage indicating a problem.
But for ease of use ... and readability - Digital.
Oh I have a complaint ... why do they use tiny symbols on them instead of AC ..... DC ..... etc. ? Unless you have a magnifying glass on some - you can't tell what they are !! Yes my eyes are getting worse ....
davierobb
Well-Known Member
I bought a £5 digital MM from Aldi/Lidel, its the dogs bollox for use on the boat. However it did lead me up the garden path when an analogue meter would not have. If you have a break in a cable with corrosion around the break then a digital MM may still measure 12V or whatever.
For finding these type of faults an analogue meter or a light bulb and croc clips is best. IMHO
For finding these type of faults an analogue meter or a light bulb and croc clips is best. IMHO
VicS
Well-Known Member
I can't disagree with the bulb on leads. Almost infallable, fragile I suppose, but cheap.
Some other valid points in favour of analogue meters have been mentioed as well.
Another that I can think of is spotting reversed polarity. A digital meter reads but shows a minus sign in front of the reading which is easily overlooked. An analogue one just goes back against the stop then it is obvious. That wasted a lot of my time trying to figure out why a fluorescent lamp did not work on a friends boat. It was the second he had tried after taking the first one back! It worked of course when I tried it on the car battery. He had connected his battery up the wrong way and with no electronics or other polarity sensitive equipment or charging he had not noticed and neither did I.
Regarding running the battery flat if left switched on, the slightly better digital ones do have an auto-off feature.
I'm going to stick with my £5 Maplin digital nevertheless!!!!!! Well one was £5 the other was half of a two for £5 offer. My son had the other one and he is an electronics engineer.
Some other valid points in favour of analogue meters have been mentioed as well.
Another that I can think of is spotting reversed polarity. A digital meter reads but shows a minus sign in front of the reading which is easily overlooked. An analogue one just goes back against the stop then it is obvious. That wasted a lot of my time trying to figure out why a fluorescent lamp did not work on a friends boat. It was the second he had tried after taking the first one back! It worked of course when I tried it on the car battery. He had connected his battery up the wrong way and with no electronics or other polarity sensitive equipment or charging he had not noticed and neither did I.
Regarding running the battery flat if left switched on, the slightly better digital ones do have an auto-off feature.
I'm going to stick with my £5 Maplin digital nevertheless!!!!!! Well one was £5 the other was half of a two for £5 offer. My son had the other one and he is an electronics engineer.
mikejames
Well-Known Member
Re: What damage and why?
If you are rich or choosy, go for something like the Fluke meters.
These have a fast bar graph updated 20 times a second and a digital display updated three times a second with a range of reading from 0.0000 to 3.9999 rather than 0.000 to 1.999 of simpler meters.
The bar graph shows quick trends and the digital display shows accurate steady readings, which is what you need.
I have done more damage slipping with meter probes across contacts making shorts than with any meter. I once blew the ends off a motorbike battery when I sparked some hydrogen in it while I was measuring the cell voltages .
If you are rich or choosy, go for something like the Fluke meters.
These have a fast bar graph updated 20 times a second and a digital display updated three times a second with a range of reading from 0.0000 to 3.9999 rather than 0.000 to 1.999 of simpler meters.
The bar graph shows quick trends and the digital display shows accurate steady readings, which is what you need.
I have done more damage slipping with meter probes across contacts making shorts than with any meter. I once blew the ends off a motorbike battery when I sparked some hydrogen in it while I was measuring the cell voltages .
