Multi meter recomendation

[jonjo]

I think I will have to buy a multi meter to aid the discovery process into the new boat's electrics. Do I need anything fancy or marinized?

The following looks reasonable to me at £15, it does AC as well. Are there other features I should be looking for, maybe one that comes with a sealed case to aid a long-life at sea?

http://www.tlc-direct.co.uk/Products/TMM3800.html

 

[jimboaw]

Cheapest you can find. $9.99 over here. If it breaks before the bat goes flat deep six it

 

[jfkal]

Do yourself a favour and get a good one. One with DC Ampere (clamp on type) is an excellent helper. Want to know whether the alternator is charging? Just clamp over the cable and pronto you can read up 100 Amps without a single wire to be attached. They are not cheap approx. 80 GBP but worth all of it. Beware of the cheapos who can only measure AC Amps they are of no use.
For hunting stray and galvanic current get the cheapest analog you can find. Most digital ones are too sensitive give you high voltage readings which otherwise would collapse under a small load.

 

[mtb]

I brought mine from Tandys about ten years ago cost then £45 but does what it's supposed to . They are very good re price quality and range, I prefer the old style to digital.
cheers
Mick

smile you'l be on your boat soon ;-)
<A target="_blank" HREF=http://homepage.ntlworld.com/boats/>http://homepage.ntlworld.com/boats/</A>

 

[extravert]

Maplins for a while have done two for £5. They measure DC amps, amongst other things. I can't really see that it is worth spending any more as the all that you are really interested in on a boat is measuring continuity, low voltage DC and perhaps charging current. Expensive ones get lost, stolen, damaged...cheap ones seem to go on for ever. These really are so cheap that you can leave them on board and if they die, so what?

Adventures of the <A target="_blank" HREF=http://www.xrayted.fsnet.co.uk>Teddy Bear Boat</A>

 

[Strathglass]

There is only one place I have found to buy a good multimeter it is

<A target="_blank" HREF=http://www.cybermarket.co.uk/ishop/923/shopscr91>http://www.cybermarket.co.uk/ishop/923/shopscr91</A>

You will find a range of multimeters. For general use the one at £23 offers very good value for money and is infinately more rugged than the cheeper ones especially the leads. I myself purchased the £45 several months ago as I required the high accuracy and 20Amp AC current capacity and am delighted with it. There is nothing on the market anywhere the performance at the price. They also do the cheeper ones as well but I have found them to have a very low life expectancy.

<font color=red>Iain</font color=red>

 

[Aeolus_IV]

Just went into nearest motor parts shop and spent £10 on digital meter - does everything except sensing amps (does do "in-line amps" - no good for charging circuit though). Worked for me while re-wiring 12v system on boat.

Jeff.

 

[jonjo]

Re: Clamp clarification

I went to the site suggested by Ian Simpson and found some clamp-on models, £60 would buy a model that covers DC charging amps. The "clamp-on" bit seems to be just a simple plastic mechanical hands free device, have I misunderstood?

http://www.cybermarket.co.uk/ishop/923/shopscr1551.html

 

[Aeolus_IV]

Re: Clamp clarification

No, it means you can measure ampage running through a cable without breaking the cable and putting the multi-meter "in-line" so the current runs through the meter. Really the only way to measure high ampages unless you install a shunt and a suitable meter across it.

Jeff.

 

[jonjo]

Re: galvanic current collapse

> For hunting stray and galvanic current get the cheapest analogue you can find

A topical and significant point, I had not thought of that function. Thanks.

 

[jonjo]

Re: Magnetic field?

Intriguing, does the clamp interpret the magnetic field?

 

[Aeolus_IV]

Re: Magnetic field?

Yes - but I thought that they only worked on AC, and at that only if you can get the clamp round just 1 of the wires (other wise live and neutral currents magnetic fields cancel each other out). I'm sure someone will fill us in wth the missing details.

Jeff.

 

[jfkal]

Re: Clamp clarification

Yes and no. For high currents the clamp on is used because:
Otherwise up 100 A would go through the instrument requiring massive shunt resistors and you would have to unscrew your thick cables and bolt them to the instrument. Not very practical if you only want to do a quick check on how many amps are being cranked out, How much goes into batt 1 and batt 2 or how much is "house" drawing currently and so on.
Remember: Always clamp on to Single wire only. If you clamp over + and - you will get zero reading.
What you describe as a simple plastic thing is actually an sensor picking up the magnetic field around the wire which gets stronger the higher the current.
Once you clamp over both cable the field gets canceled out.
Nice feature is also that you see whether amps go into the battery or out of the battery.
Hope that helps. BTW the price you indicated is reasonable for a DC amp instrument

 

[HaraldS]

Re: Magnetic field?

You can get AC and DC. AC is cheaper and more common and works on induction. The DC ones use a semiconductor probe called a Hall-sensor.
I can only second that this (the DC one) is very useful on a boat, especially so because it is relatively easy to grab a single wire here and there.
But don't expect it to measure small currents very well, anything below an Amp is dubious. You also need to calibrate zero reading every time you turn it on.

<A target="_blank" HREF=http://www.taniwani.de>http://www.taniwani.de</A>

 

[rogerm]

You might like to think of buying a specalist low voltage meter. I am particularly thinking of 'Gunsons' avaliable from Halfords and other motorists shops for about £30 (as I recall). It comes with a shunt so that currents upto 100A can be measured which is particularly useful for checking alternators and has a 'dwell' range for checking RPM and points (if you still have any).

I always put electrical/electronic kit that is in infrequent use in one of those re-sealable polybags along with a small silica-gel packet to help them survive marine use.
Roger

 

[neil_s]

Maplin do a serviceable one for a fiver!

www.maplin.co.uk


Cheers! Neil