Multimeter

pessimist

pessimist

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My old multimeter has given up the ghost and I'd rather like to replace it with one of the clamp type. Most use would be on the boat so I'd like to have a DC current measuring facility.

There seems to be a wide variation in prices and I'm wondering if I'd just be wasting my money on one of the cheapies, something like this http://cgi.ebay.co.uk/UNI-T-DC-clam...sGames_RadioControlled_JN?hash=item27adb0ddf2.

Any thoughts welcome.
 
Multimeters can be picked up really cheaply these days from a wide variety of places. Maplins have them at around a fiver, similar ones can be picked up on tool stalls on Sunday markets etc for as little as £3 if you're lucky.

The good thing about them is that not only are they cheap, but also very small and compact too, and amazingly accurate. Don't ask me how they do it for the money, just enjoy the benefits!
 
I have something that looks very similar, bought from Maplins (IIRC at lower price). The clamp feature is to measure AC current. The stated current range on the spec seems pretty high, don't think I'd like to push 400 amps through it. It seems to work fine and is fairly repeatable. I'd rather buy another one in a couple of years when it's broken, especially in the marine environment, than pay a lot more for a "high brand" product (which probably has the same internals, anyhow!).
 
Just a reminder that clamp meters require a single wire only, so you need to get back to the point of connection or split a multi core cable.

I got one from China for the boat and van, works very well and cost less than AU$35.00 including P&P.
 
Clamp type multimeters are for measuring high currents. The clamp is made of a soft ferrous material and acts like the core of a transformer. You can probably push 10 times the current 'through' the meter without doing anything more than overscaling it*. The power is not transmitted into the meter, the meter is measuring the emf off the cable.

A clamp meter is pretty much useless on a 12/24v marine installation except for measuring the starter motor cranking current. ( 200 - 600 amps ? ) A good quality digital multimeter is a far better investment. A Fluke or similar will last many years even in a harsh marine environment. My old 77 is more than a quarter century old now!


* Not that I'd like to be anywhere near a 4000 amp cable on a boat! I once did some work on some Programmable Logic Controller equipment inside a steelworks. The main furnace was pulling down around 45000 amperes at 500 volts. The effect on surrounding equipment was 'interesting' to say the least.
 
Clamp meter

The one on ebay appears to have a minimum current of 40 amps - if this is the case it would not be a much use on most boats. In A/C terms that's 3 or 4 kettles simulataneously & for DC only good for measuring some of the output of chargers & alternators.
The last time I bought [don't know where] one it was around £100 - beware the cheapest usually are only capable of measuring A/C current. No reason why a decent one should not read to 0.1 of an amp.

John G
 
The one on ebay appears to have a minimum current of 40 amps
Click to expand...
40 amps is the lowest of its two ranges . The equivalent of 40A full-scale on an analogue meter

With a four digit display I'd expect that range to be 40.00 amps so potentially a sensitivity of 0.01 amps .
 
I would be very warey of buying some items on Ebay for two reasons.

1. You don't know how good and in this case safe the product is. What if it goes wrong?

2. I don't like handing my credit card details out to people.

I would just buy one from Maplins.
 
Do you have an ammeter installed on board? I'd have thought that would be all you'd need - just turn the item in question on and off and calculate the difference. If you don't have one it's a very worthwhile investment.
 
pessimist said:
My old multimeter has given up the ghost and I'd rather like to replace it with one of the clamp type. Most use would be on the boat so I'd like to have a DC current measuring facility.

There seems to be a wide variation in prices and I'm wondering if I'd just be wasting my money on one of the cheapies, something like this http://cgi.ebay.co.uk/UNI-T-DC-clam...sGames_RadioControlled_JN?hash=item27adb0ddf2.

Any thoughts welcome.
Click to expand...

I buy a lot of gear from this company. The quality & service is good. They are out of stock of the cheapest Dc clamp meter.

http://www.rapidonline.com/Tools-Fa...quipment/Clamp-Meters/AC-DC-Clamp-meter/74582

I
 
VicS said:
40 amps is the lowest of its two ranges . The equivalent of 40A full-scale on an analogue meter

With a four digit display I'd expect that range to be 40.00 amps so potentially a sensitivity of 0.01 amps .
Click to expand...

I bought one of these from CPC some time ago and as Vic says on the 40A range you can, theoretically, measure down to 10mA but in practice I think 100mA is about the limit for DC current measurement as the reading changes by a few mA even when no current is flowing. The one I have is no longer available but this one http://cpc.farnell.com/tenma/72-7224/clamp-meter-with-frequency/dp/IN0511003?Ntt=IN0511003 looks very similar and at £25.79 looks to be a good deal and saves having to break into a circuit to see if there is any current flowing.

John
 
My contribution is keep it as simple as possible. How many scales do you really need on a boats multi meter?

Digital or analogue? The digital sort can be confusing as even cheap ones have a very high input impedance (resistance) . Is it a reading or just noise ?

The analogue variety at least have to draw some currant to produce a reading on a scale. Do you really need even two places of decimals?

A clamp on ammeter is a fantastic diagnostic tool. Is there a current flow (in a cable) or not? Is it a big flow or a little one.? Which way is it flowing?

OK, this may be over simplified but, keep it simple, keep it cheap go analogue!

73s de
Johnth
 
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