Voltmeter

[JohnL]

Help please,I intend to fit a voltmeter to my boat, problem is there are three terminals two are spade type marked +/- which give a reading on the meter OK but there is a post termial marked S, can anyone tell me what this is for. There are also two obvious leads for the light, thanks in advance.

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[Rich_F]

Can't help directly, I'm afraid, but I do have a related question.

I'm wanting to fit a digital voltmeter to my boat, and want to know if anyone knows where I can get a cheap one. I'm finding it irritating that digital multimeters can be got at very low prices, but a dedicated panel-fitted voltmeter costs upwards of £50.

And while I'm here... I also thought that it would be useful to fit an electric water tank gauge. Any cheap solutions for this? I'd have thought that a water pressure transducer fitted in the outlet pipe would be the simplest solution, but the commercial offerings seem to involve floats, etc, and are around £100 for a complete solution.

Thanks,

Rich

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[Gunfleet]

Why don't you just use the digital handheld? You have to wait half an hour after charging or discharging for an accurate reading, but it will give you a very accurate picture of your battery's condition.

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[duncan]

Many of your electronics could already have one for you - both my sonar units enable we to show volts in a seperate window or overlayed on screen if I require as does one chartplotter.


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[oldsaltoz]

G'day JohnL,

You say there are 2 more wires for the light, is this an instrument or warning light?

If it's an instrument light the remaining wire may well be a 'S' signal light, If you have a multi meter, try connecting a 12 volt globe and your meter between it and earth to what sort of voltage is running thru'.

Hope this helps


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[philwebb]

Hi John,
Does your voltmeter give an accurate reading when you use just the two spade
terminals? If so you can probably disregard the other terminal . The S may stand for
shunt - actually a series resistor on a voltmeter, which might be used to give the
voltmeter an extra range eg 0-50 volts instead of 0-20 volts. A moving coil voltmeter
(with a needle) is really an instrument measuring a small current. With the addition of a large series resistor it can be calibrated to measure voltage.
Regards,
Phil
PS RichF-have you tried MAPLIN-they do cheap electronic components.

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[Rich_F]

Thanks - good point. I've just acquired a fishfinder with voltage display, so I can use that.

But in addition, while I'm rewiring the panel, I think that I'll add a chocolate-block of test points for measuring various voltages in the system from one convenient location.

Cheers,

Rich

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[Evadne]

It could be a shunt az Oz suggests or possibly a screen (i.e. ground) which you would connect if the wires needed screening. Sometimes you can find deails on a manufacturers website of quite obscure instruments.


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[pete]

Hi
I also wanted to fit a digital volt meter to my boat but was put off by the price I got one in the end from RS, it measures about 30mmx20mm and cost around £30 inc p&p.
Pete

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[LadyInBed]

Re: Multimeter

Your local cheapy hardware shop (Anything-for-a-pound or the like) will have cheap multimeters, £3.50 to £6.99.
I bought two from Liddles when they has them in @ £3.50, perfectly adequate to leave on the boat.
I can then keep my expensive Fluke at home.

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[duncan]

Re: Multimeter

an answer to a question I have been mulling over! thank you. Having decided not to leave my 'quakity' mm onboard I inevitably didn't have it with me on the last two trips and needed it! It's off to Liddles then.....

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[LadyInBed]

Re: Multimeter

Liddles are great, but you know how they work - they get a item in then when it's gone it's gone till they repeat the cycle 6 months to a year later.

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[pvb]

The S Terminal...

The voltmeter should work fine without using the S terminal.

The most likely explanation for the unnecessary S terminal is to enable more economical manufacturing of the gauge. Most gauges have a sensor connection (hence S) and I'd imagine the manufacturer considered it cheaper to use a common body for all gauges rather than having a dedicated body for the voltmeter.

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[HaraldS]

If it has a metal housing, the S-post might be connected to it and stand for "Screen". In that case you wouldn't really need it, but I had my digital AMP-meter go crazy when I was anchord next to a huge AM radio station. Grounding the screen of the cable that goes to the shunt helped a lot but not completely and I wished mine had a screen to connect.

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[bedouin]

As others have said - a cheap digital handheld will cost you about £5 and will do the job perfectly well. The only disadvantage with this is that they require a separate battery - and cannot be run from the boat battery (because they like their internal supply isolated from the supply which they are sensing).

If you want a posher one, capable of being powered by the same supply that it is sensing - then you will have to pay a lot more. RS do a very nice one with two-wire connection - this costs about £25 and is identical to one being sold by marine retailers for > £50

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