AMPAGE TESTING (12 Volt DC)

[srands]

Useful reference guide for AMPAGE TESTING of 12 Volt DC.



PICTURE VERSION URL:
https://blufiles.storage.live.com/y...znmbCQXpJVytYH2xzFs/AmpageTesting12VoltDC.jpg

WORD VERSION URL:
https://skydrive.live.com/view.aspx?cid=9EC5688DD90EEC6C&resid=9EC5688DD90EEC6C!581

TOOLS NEEDS:
MULTIMETER, SCREWDRIVERS & BLOCK CONNECTORS

This is quite simple see following pictures (Much easier to do then first impression on reading instructions), the MultiMeter in this instance (DRAWN, POSITIVE TERMINAL) tests the AMPAGE between the POSITIVE SUPPLY (red probe lead) and the POSITIVE LOAD (black probe lead). Hence the NEGATIVE is uninterrupted from SUPPLY to LOAD (In other words, leave it alone). In this instance the positive supply has croc clips, normally I'd use insulated BLOCK CONNECTORS:
PIC1 (multimeter measuring AMPAGE between POSITIVE supply & POSITIVE load)

PIC2 (12V dc Battery Charger powering car cd player, with MultiMeter Testing AMPAGE)

PIC3 (CAR CD PLAYER in house install powered by CAR BATTERY CHARGER 12 V dc 4A)

PRECAUTIONARY NOTEs:
~ Obviously the NEGATIVE and POSITIVE can NOT touch each other (Neither SUPPLY or LOAD)
~ If your MultiMeter has NEGATIVE READING, then means you have your PROBE LEADS the wrong way (Or just ignore the negative symbol, as the AMPAGE figure will be accurate).
~ The 12V dc MOTOR/PART or ALTERNATOR/SOLAR PANEL may CHARGE/DRAW a greater AMPAGE/CURRENT then the capacity of the MULTIMETER & its LEADS (At this point the actual ampage is unknown). For example most car electrical parts are low current (Indicators, elec windows, elec sunroof, heater, etc), with the obvious exception of a car starter motor (Extremely high ampage/current, totally unsuitable for testing with MultiMeter). Hence if the 12V dc part/motor or the charge rate of the power supply is greater then 10A this may melt your MultiMeter probe leads and/or break the MultiMeter (Unless you have a 20A DC MultiMeter! Obviously the ampage max of those is 20A DC).

OTHER NOTES:

~ The AMPAGE reading given by your MULTIMETER, is given by testing 'A' POSITIVE or 'A' NEGATIVE, however the AMPAGE reading is the total AMPAGE drawn/charged, so this figure should NOT be doubled in your calculations.

~ If you're testing direct from a car battery and it's loom, it may have other parts/motors draining ampage, such as indicators/wipers, etc. So turn ON the ignition (WITHOUT STARTING THE CAR, as the ampage drain would be far too great for the MULTIMETER & PROBE LEADS!), then make a note of what the standard ampage drain is approximately (i), then turn on the motor/device/appliance you want to test (ii). Then subtract the standard ampage drain from the new figure with the appliance/device/motor on to EQUAL the difference (iii) i.e. The ampage of the motor/part etc.
FOR EXAMPLE:
i) STANDARD AMPAGE DRAIN = 0.5a (Car alarm or something else)
ii) STANDARD AMPAGE DRAIN & OTHER MOTOR = 1.5a
iii) CALC 1.5a - 0.5a = 1.0a

Alternatively (my preferred practice/method) connect new leads to the battery terminals, so there won't be any other registered ampage drawn from the car battery. So the ampage reading is what it is!
PS. Don't mess about from behind the car fusebox, keep it simple, either direct from car battery and loom OR new power leads from car battery to motor/part/device/appliance your testing with a MULTIMETER.

I made this guide as a quick reference when testing 12 Volt DC circuits with a MultiMeter, EITHER:
~ ampage CHARGE to batteries
OR
~ ampage DRAWN from batteries.The main reason for this guide is that I was not impressed (And continue to be not impressed with the lack of meaningful instructions) with uncomprehensive manuals supplied with most MultiMeters. Seems odd to make a great feature but don't explain in the instructions.

Remember most MultiMeters (£10 Maplin job ok) only test upto 10A 12V DC, more expensive MultiMeters (UNI-T from Maplin £30 why spend any more) test upto 20A 12V DC.

ALTERNATIVELY To test AMPAGE of 240 VOLT APPLIANCES use a plug in ENERGY MONITOR (From Maplin).

This guide I'm sure will be a great help to test 12 Volt DC circuits, however please feel free to add these links below (Website addresses, urls, etc), the numerous number of posts on this subject (That I couldn't find), and web references to wiring regulations, and any other derogatory negative remarks you have as well!

CHEERS, AND BELOW IS A FULL LIST OF MY OTHER USEFUL GUIDES & SPREADSHEETS (Top entries of electrical interest)

STEPHAN RANDS
AMPAGE TESTING (12 Volt DC)
RING AMP AUTOCALC: 1ST TAB
LIGHTING CIRCUITS, RING & RADIAL wiring diagrams
UTILITY ENERGY MEGACALC
MPG
METRIC AUTOCALC
PERCENTAGE CALCULATOR AUTOCALC
EXCEL USEFUL FORMULAS
MTB ROUTES IN/NEAR HULL, HUMBERSIDE
TIER 4+ CATEGORY TYPE
TIER 4+ MONEY TYPE
AUTOCALC WEBSITE

 

[srands]

Thanks for link to Ampere-hours, you learn something everyday!
Could you please explain to me kWh, I'm just completely baffled by them?
Thanks in advance
A

This needs explaining from both 12 Volt DC and 240 AC Volt perspective:

12 Volt dc, we're NOT concerned about the cost of electric, because a car alternator generates this for free (Well apart from fuel & wear & tear of car & driver!) as is a by product of engine running (One cog turns, a belt to the alternator, another cog turns, electric produced, power lead to battery, charging battery). Hence the only real preoccupation here is what is the AMPAGE of the PART (If unknown use MultiMeter to determine, see 1st msg in this post)? Once this is known, then specifying the correct THICKNESS LEAD/CABLE and FUSE is one of the only fitment considerations

Calcs (W = Watts, V = Voltage, A = Amps):

1000 W's = 1 KW (In other words W * 1000 = KW)

A x V = W (Eg 0.8A * 12v = 10Ws)

W / V = A (Eg 10Ws / 12v = 0.8A)

Ah x 10 = A (EN) (Eg 56 Ah * 10 = 560 A [EN])

DC 12 Volt Cable Guide
Individual insulated wire thickness in mm with approx max	AMPs	WATTs
2.7mm	3A	36w
3.0mm	10A	120w
3.8mm	20A	240w
5.0mm	35A	420w
6.2mm	50A	600w
1.2CM	AWG8 / 40A	480w
1.6CM	AWG4 / 70A	840w

Note: To power an AC 240 Volt appliance in a car, you need an INVERTER (I'd recommend a very generous maximum margin to power your SMALL appliance, such as I have fitted 1000W Inverter for a 100W LAPTOP!). WHY? Because your laptop voltage is different to your car battery, for example: Car batteries = 12V. My Laptop power = 20V with psu (Power Supply Unit AC to DC). And bigger is always better, as may use USB powered extras (Hard drive, cameras, etc), or may get larger spec laptop.

240 Volt ac, we ARE concerned about the cost of electric, because ELEC is charged by the KW.
Small Appliances are stated in WATTs (This figure is the approx figure IF an appliance is used for AN HOUR, even though the reading on ENERGY MONITORS is instantly displayed. For example a kettle may only be used for 3 mins, and it's max maybe 2200 Watt's, however it's consumption is NOT 2200 Watt's unless it is used continuously for an hour!).
Large Appliances over 1000 Watt's are stated in KiloWatts such as KETTLES, DISH WASHERS, WASHING MACHINES, etc.
ELECTRIC used in houses/businesses is measured with an ELECTRIC METER, and in KWs.
Once again specifying the correct THICKNESS LEAD/CABLE and FUSE is an important fitment consideration. Since appliances already come with a LEAD, the same thickness or bigger is adequate. The FUSE must be greater then the Ampage max of the appliance and the cable lead must be thicker Ampage then the fuse Ampage.
However if fitting new SOCKET RING/RADIAL circuit need to be fitted, consideration has to be given the total max in amps of all applainces using that circuit, hence use appropriate socket wire cable, sockets/fixtures, etc.

AC 240V (Appliance Wire) Cable Guide
Individual insulated wire thickness in mm with approx max	AMPs	WATTs
0.2mm	1A	240w
0.5mm	3A	720w
0.75mmm	6A	1440w
1.00mm	10A	2400w
1.25mm	13A	3120w
1.5mm	15A	3600w
2.5mm	20A	4500w
4.00mm	30A	7200w

AC 240 Volts (Socket/W) Cable Guide
Individual insulated skt wire thickness in mm with approx max	AMPs	WATTs
1mm	15A	3600w
1.5mm	20A	4800w
2.5mm	27A	6480w
4mm	36A	8640w
6mm	46A	11040w
10mm	63A	15120w
16mm	85A	20400w

Want a FUSEBOX CIRCUIT and MCB/RCD calculator? See my spreadsheet MCB/RCD CALC See the 3rd tab (If MCB's are different ampages) or 4rd tab (If MCB's are same ampage)


Calcs (W = Watts, V = Voltage, A = Amps):

1000 W's = 1 KW (In other words W * 1000 = KW)

A x V = W (Eg 5A * 240v = 1200Ws)

W / V = A (Eg 1200Ws / 240v = 5A)

Note: To power a DC 12 Volt appliance in a house, you need either an adequate:
~ AC to DC plug: Maplin stores, Mobile phone stores, or stalls in retail shopping centres)
or
~ AC to DC psu (power supply unit): Maplin stores
or
~ CAR BATTERY

Still need more ELEC/utility calculators? See my very comprehensive workbook spreadsheet (See 1st tab, scroll down) ELEC GAS WATER autocalc: 1st tab, scroll down

 

[Knobhead]

You can’t even recognise sarcasm!
View attachment 7913

 

[Silly Sausage]

You can’t even recognise sarcasm!
View attachment 7913

I bumped into him on my way into Maplins to pick my pre ordred ampage meter.
He's not a patch on his mate srands though, showed me a picture he whipped out of those trousers.

 

[Knobhead]

These ampage meters, are they any good and how expensive are they?

Was it a picture of str**ds.

View attachment 7914

 

[Silly Sausage]

No, that's his shy brother