Which Multimeter

[Doug the Tug]

I keep hearing that the most important piece of kit for a boat owner is a multimeter. Not sure if that is true, but it would seem sensible to have one and learn how to use one.

As I live close to a CPC outlet, I searched their website (www.CPC.co.uk) for multimeter and got about 100 products to choose from. As a complete novice the only way to choose would be to assume more expensive means better quality. Whilst that statement is probably not true anyway, even if it were, I would then spend a lot of money on a piece of kit that is far to good for my needs and abilities.

 

Anybody out there able to give a novice some good advice?

[Guest]

I keep hearing that the most important piece of kit for a boat owner is a multimeter. Not sure if that is true, but it would seem sensible to have one and learn how to use one.

As I live close to a CPC outlet, I searched their website (www.CPC.co.uk) for multimeter and got about 100 products to choose from. As a complete novice the only way to choose would be to assume more expensive means better quality. Whilst that statement is probably not true anyway, even if it were, I would then spend a lot of money on a piece of kit that is far to good for my needs and abilities.

 

Anybody out there able to give a novice some good advice?

Expensive ones will always be most reliable. Fluke are best if you can spare a few hundred quid. We use these to good effect at work, and they are accurate within reason at 12V DC. I have one on the boat, and one in the house as they are so cheap. If it gets nicked off the boat or dropped in the cut I won't be too upset.

 

http://www.rapidonline.com/Tools-Fasteners.../kw/multi+meter

[blackrose]

I keep hearing that the most important piece of kit for a boat owner is a multimeter. Not sure if that is true, but it would seem sensible to have one and learn how to use one.

As I live close to a CPC outlet, I searched their website (www.CPC.co.uk) for multimeter and got about 100 products to choose from. As a complete novice the only way to choose would be to assume more expensive means better quality. Whilst that statement is probably not true anyway, even if it were, I would then spend a lot of money on a piece of kit that is far to good for my needs and abilities.

 

Anybody out there able to give a novice some good advice?

 

It very much depends on what you want to use it for. Cheap multi-meters bought for a tenner or so are fine for general use - checking that you're getting a voltage. These often have an accuracy of about +/- 0.5v. However, if you want to know the state of charge of your batteries and are using voltage to check this, or you want to calibrate a battery monitor, you will need something more accurate (+/- 0.3v).

 

I think even checking voltage drop through cables will need a reasonable degree of accuracy.

 

If you compare the figures of voltages for say an 80% charged battery bank and a 60% charged bank, the difference between a meter with an accuracy of +/- 0.3v and +/- 0.5v will be obvious. The less accurate meter will be be almost useless.

Edited October 31, 2009 by blackrose

[Guest]

It very much depends on what you want to use it for. Cheap multi-meters bought for a tenner or so are fine for general use. These often have an accuracy of about +/- 0.5v. However, if you want to know the state of charge of your batteries and are using voltage to check this, or you want to calibrate a battery monitor, you will need something more accurate (+/- 0.3v)..

 

I think even checking voltage drop through cables will need a reasonable degree of accuracy.

 

If you compare the figures of voltages for say an 80% charged battery bank and a 60% charged bank, the difference between a meter with an accuracy of +/- 0.3v and +/- 0.5v will be obvious. The less accurate meter will be be almost useles.

In theory you are spot on. The higher accuracy meter should always give the most accurate reading. In practice I have found that all but one of the cheapo meters we have bought from Rapid over the years (down to around six quid now, I see) have been within a couple of hundredths of a volt of the master meter at work, all measured on a calibrated power supply. I can't explian why this is so, but my two (then) ten quid Rapid meters compare very favourably with my super posh multimeter (make forgotten) when measuring the 12V dc voltages that we are discussing here. I rarely use my good one now for fear oflosing/damaging/submerging it. Can't say I have tested them a great deal at higher voltgages though. At six quid, and accurate enough, I consider them "free."

[alan_fincher]

It very much depends on what you want to use it for. Cheap multi-meters bought for a tenner or so are fine for general use - checking that you're getting a voltage. These often have an accuracy of about +/- 0.5v. However, if you want to know the state of charge of your batteries and are using voltage to check this, or you want to calibrate a battery monitor, you will need something more accurate (+/- 0.3v).

I think even a meter that is accurate to +/- 0.3 volts when measuring at around 12 volts will not be accurate enough to give a good idea of state of charge, and the like.

 

What the experts have said previously is that the multimeter needs to have an accuracy of at least +/- 0.5 percent, (not volts), on the relevant DC range. That effectively will translate to a much greater accuracy, namely +/- 0.1 volts. (IIRC 0.1 volt represents about 10% of discharge on a 12 volt boat battery, so anything less than that will not really be a lot of use).

 

It doesn't have to be expensive to get +/- 0.5% accuracy on a DC volts range - you can buy ones that accurate at only a tenner!

[blackrose]

I think even a meter that is accurate to +/- 0.3 volts when measuring at around 12 volts will not be accurate enough to give a good idea of state of charge, and the like.

 

What the experts have said previously is that the multimeter needs to have an accuracy of at least +/- 0.5 percent, (not volts), on the relevant DC range. That effectively will translate to a much greater accuracy, namely +/- 0.1 volts. (IIRC 0.1 volt represents about 10% of discharge on a 12 volt boat battery, so anything less than that will not really be a lot of use).

 

It doesn't have to be expensive to get +/- 0.5% accuracy on a DC volts range - you can buy ones that accurate at only a tenner!

 

ah I got my figures wrong!

[Doug the Tug]

Thank you Catweasel, this is exactly the sort of answer I needed. A trusted recommendation based on personal experience for a fit for purpose meter at a sensible price.

I will buy one - well as the boat will not be ready until Easter, I may pass on your recommendation to Santa.

 

Thanks again,

Doug

[alan_fincher]

Catweasel's recommendation looks a good one.

 

However note the following in it's spec.....

 

Fuse protected on all ranges except the 10A DC current range (for suitable replacement fuse see <www.rapidonline.com )

This means if you plug leads in the socket designed to measure high DC currents, and then connect it across a voltage source, (e.g. boat battery), you will likely see the impressive sight of smoke poring from your meter, whilst the test leads suffer melt down.

 

....... But, please, don't ask me how I know this!

[ditchcrawler]

Catweasel's recommendation looks a good one.

 

However note the following in it's spec.....

 

 

This means if you plug leads in the socket designed to measure high DC currents, and then connect it across a voltage source, (e.g. boat battery), you will likely see the impressive sight of smoke poring from your meter, whilst the test leads suffer melt down.

 

....... But, please, don't ask me how I know this!

When I was a work we changed all meter test leads to fused leads, guess why

[Gibbo]

Expensive ones will always be most reliable. Fluke are best if you can spare a few hundred quid. We use these to good effect at work, and they are accurate within reason at 12V DC. I have one on the boat, and one in the house as they are so cheap. If it gets nicked off the boat or dropped in the cut I won't be too upset.

 

http://www.rapidonline.com/Tools-Fasteners.../kw/multi+meter

 

One problem to be aware of with this meter is that as the batteries go flat the reading loses accuracy. Quite badly.

 

This one.......................

 

http://www.tooled-up.com/Product.asp?PID=7...eferrer=froogle

 

Has been tested in our workshop for accuracy and we've had 3 of them being used daily for a couple of years now without any issues. Accuracy is stunning for the money.

 

Yes I know it's substantially more expensive but it's still a relative bargain compared to a Fluke (which are the best without question) and I have seen them around £25.00

[Guest]

One problem to be aware of with this meter is that as the batteries go flat the reading loses accuracy. Quite badly.

 

This one.......................

 

http://www.tooled-up.com/Product.asp?PID=7...eferrer=froogle

 

Has been tested in our workshop for accuracy and we've had 3 of them being used daily for a couple of years now without any issues. Accuracy is stunning for the money.

 

Yes I know it's substantially more expensive but it's still a relative bargain compared to a Fluke (which are the best without question) and I have seen them around £25.00

We have one of those at work too, but with a different name on it. Again it is very accurate in the low DC voltages when compared to the master. Well worth the money I would think. We paid a bit more than that IIRC, but like many things the price has dropped.

I must say that the cheapo ones from Rapid have survived well despite being hammered by school kids. Interesting about the battery though, we change them frequently so have not picked up on that.

[Gibbo]

http://www.pvrdirect.co.uk/productinfo.asp...apitest-RAPDM25

 

Look at that price!

[Nickhlx]

I have several multimeters from the cheapo £5 ones to the low priced ones at £30, which I do tend to use the most - however being worried about accuracy, I built a 10.000 volt reference voltage with an off the shelf chip which "guarantees" its output to be within 5 millivolts of 10.000 volts, and use this to check and calibrate the accuracy of all meters periodically. Initial checks did show the meters to be within about 150 millivolts of the reference, some high and some low, which gave me a lot of confidence that the box worked.

 

So, I am happy it does produce close to its claimed 10.000 volts - when on a 20 volts scale, when it reads 10.00 volts ( 3.5 digit meter) I am confident it is somewhere between 9.995 and 10.005 volts. At 12 volts it may be a further millivolt out, say between 9.994 volts and 10.006 volts...

 

The point is, assuming it is working as intended, and I have no reason to doubt, I can believe the meter to within 0.02 volts ( 20 millivolts ) and certainly to within 0.1 V (100 millivolts) which is the accuracy I was needing to correctly read the battery voltage. ( awaits Gibbo's blessings )

 

I am happy to scan the circuit I built and e-mail to anyone who may be interested..

 

Nick

[Gibbo]

I'd guess at the LT1031B ?

[Guest]

http://www.pvrdirect.co.uk/productinfo.asp...apitest-RAPDM25

 

Look at that price!

Having seen that I would pay the 18 quid or thereabouts and go for one of those. I am sure they were once around 35 or 40 quid. Amazing value.

[Nickhlx]

I'd guess at the LT1031B ?

 

 

Will try and find the circuit ! .....

 

Re the OP's original question for suggested meters, have a look at the Maplin UT50A at £19-99... http://www.maplin.co.uk/Module.aspx?moduleno=46390

 

This has amongst other things a 20 amp range which may be more useful than the 10 A range of many, and DC best accuracy of 0.5% ( others 0.8% ), which gives a good starting point..

 

Nick

[Gibbo]

Will try and find the circuit ! .....

 

Re the OP's original question for suggested meters, have a look at the Maplin UT50A at £19-99... http://www.maplin.co.uk/Module.aspx?moduleno=46390

 

This has amongst other things a 20 amp range which may be more useful than the 10 A range of many, and DC best accuracy of 0.5% ( others 0.8% ), which gives a good starting point..

 

Nick

 

If it's anything like this one...........

 

http://www.maplin.co.uk/module.aspx?Module...664&doy=2m5 (substantially higher price)

 

I'd be wary. We bought three of those along with the three Rapitest DM25. They were crap. They were about 2'6" out on all ranges. I gave them away in the end.

 

There was a thread giving more details on this meter last year I think (when we bought them).

[Nickhlx]

Will try and find the circuit ! .....

 

Re the OP's original question for suggested meters, have a look at the Maplin UT50A at £19-99... http://www.maplin.co.uk/Module.aspx?moduleno=46390

 

This has amongst other things a 20 amp range which may be more useful than the 10 A range of many, and DC best accuracy of 0.5% ( others 0.8% ), which gives a good starting point..

 

Nick

 

 

Found it - actually, it was the REF102BP I went for in the end - maybe availability / price was better....

 

Powered by two 9V PP3s in a box....

 

Nick

[Gibbo]

Found it - actually, it was the REF102BP I went for in the end - maybe availability / price was better....

 

Powered by two 9V PP3s in a box....

 

Nick

 

Just checked it. It's about half the price!

[Byeckerslike]

Hi,

 

I will readily recommend my own trust multi-meter, a Fluke 25, which are available from http://www.surplustest.co.uk/product.php?id=12

I hasten to add that this is no relation to me, just that I am extreemly satisfied with my purchase of same, thro' ebay over a year ago.

 

Regards,

Rob

[alan_fincher]

Re the OP's original question for suggested meters, have a look at the Maplin UT50A at £19-99... http://www.maplin.co.uk/Module.aspx?moduleno=46390

 

This has amongst other things a 20 amp range which may be more useful than the 10 A range of many, and DC best accuracy of 0.5% ( others 0.8% ), which gives a good starting point..

 

Nick

Good meter, but please note where you have to plug the leads.....

 

I'm used to meters where the "usual" place for most functions is the bottom two sockets.

 

Do that on this one, and you are connecting to the (unfused) 20 amp DC range - a virtual short circuit.

 

(If measuring Volts or Ohms on this meter, the leads have to be plugged into the two RIGHT HAND sockets, not side by side.)

 

Again, please don't ask me how I know this. ....................

[blackrose]

One problem to be aware of with this meter is that as the batteries go flat the reading loses accuracy. Quite badly.

 

This one.......................

 

http://www.tooled-up.com/Product.asp?PID=7...eferrer=froogle

 

Has been tested in our workshop for accuracy and we've had 3 of them being used daily for a couple of years now without any issues. Accuracy is stunning for the money.

 

Yes I know it's substantially more expensive but it's still a relative bargain compared to a Fluke (which are the best without question) and I have seen them around £25.00

I bought a Fluke 75 on ebay for £50. Used but in good condition.

[ditchcrawler]

Hi,

 

I will readily recommend my own trust multi-meter, a Fluke 25, which are available from http://www.surplustest.co.uk/product.php?id=12

I hasten to add that this is no relation to me, just that I am extreemly satisfied with my purchase of same, thro' ebay over a year ago.

 

Regards,

Rob

Has anyone tried these

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...e=STRK:MEWAX:IT

[Byeckerslike]

Good meter, but please note where you have to plug the leads.....

 

I'm used to meters where the "usual" place for most functions is the bottom two sockets.

 

Do that on this one, and you are connecting to the (unfused) 20 amp DC range - a virtual short circuit.

 

(If measuring Volts or Ohms on this meter, the leads have to be plugged into the two RIGHT HAND sockets, not side by side.)

 

Again, please don't ask me how I know this. ....................

\very true, But the very comprehensive manual does appear to assume a certain level of competence, but there again, what do you expect from a very accurate meter?

[DHutch]

See also this thread http://www.canalworld.net/forums/index.php?showtopic=26008