Using a Voltmeter....
Discussion
I have a voltmeter and no Idea how to use it.
I have 2 cables, one red, one black, which I presume get plugged into the sockets in the front, Black into COM and Red into either 10ADC or V(ohms)mA.
On the front there is a Dial, around the dial Clockwise is,
OFF, 750 ACV, 200 ACV, 200u DCA, 2000u DCA, 20m DCA, 200m DCA, 10A, hFE, ->¦-, 200 Ohms, 20k Ohms, 200k Ohms, 2000k Ohms, 200m DCV, 2000m DCV, 20 DCV, 200 DCV, 1000 DCV.
So, I need to check a few things.
Charge in a battery, if the Cables are intact in a wiring loom, and to see if there is current in a few cables in the shed.
I have idea what settings to use for these tasks.
Anyone offer any guidance?
TIA
Stuart!
And before anyone says RTFM, I Lost TFM!
I have 2 cables, one red, one black, which I presume get plugged into the sockets in the front, Black into COM and Red into either 10ADC or V(ohms)mA.
On the front there is a Dial, around the dial Clockwise is,
OFF, 750 ACV, 200 ACV, 200u DCA, 2000u DCA, 20m DCA, 200m DCA, 10A, hFE, ->¦-, 200 Ohms, 20k Ohms, 200k Ohms, 2000k Ohms, 200m DCV, 2000m DCV, 20 DCV, 200 DCV, 1000 DCV.
So, I need to check a few things.
Charge in a battery, if the Cables are intact in a wiring loom, and to see if there is current in a few cables in the shed.
I have idea what settings to use for these tasks.
Anyone offer any guidance?
TIA
Stuart!
And before anyone says RTFM, I Lost TFM!
For the battery I'd use any of the DCA's, and for the wiring loom I'd use any of the DCV's...just switch it between them until you get a reading that seems about right...and for the cables in the shed, if they aren't connected to anything, there's not going to be any current in them!
Usual disclaimer applies!
Usual disclaimer applies!
Voltmeters are used across a circuit.
Ammeters are used in the circuit
Ohmmeters are used with the power to the circuit removed.
For simple volt measurements put the black lead in COM and the read lead in the socket marked V or ohm.
The ammeter set up will use the black in the COM port and the red will this time be in the other socket marked A and will probably have a warning as to it's fuse protection rating.
For resistance set up, use the same as voltmeter.
Ammeters are used in the circuit
Ohmmeters are used with the power to the circuit removed.
For simple volt measurements put the black lead in COM and the read lead in the socket marked V or ohm.
The ammeter set up will use the black in the COM port and the red will this time be in the other socket marked A and will probably have a warning as to it's fuse protection rating.
For resistance set up, use the same as voltmeter.
correct, black goes into COM
to measure charge in a battery, put the red cable cable into the DCV scale marked 0-20 - that will be accurate enough. Always start at the highest scale and work down you should never try to measure "out-of-scale".
Then you put the black cable to batter earth, the red to positive, and it will read the battery voltage.
Now, say you want to test that current is reaching, oh let's say the starter motor. leave the black cable on earth, and touch the red cable on the starter terminal. If you turn the starter over, the voltmeter should read the same as test 1 above, ie 12 volts or so.
ok so volts measures the difference in electrical charge between one thing and another, while they are connected.
DCA measures amperes - ie the current running THROUGH a cable at any time. it should be connected in series (ie remove the terminal and connect the meter BETWEEN the wire and component. In 20 years, I have never found a need to use this setting on mine, but I suppose it's useful for some things.
Ohms measures electrical resistance - DO NOT connect over live circuits. For example, you can check that a cable is not broken internally - connect the ohmmeter to each end of the cable, resistance should be zero or close to it. If there is a high resistance, might be a break or bad contact.
hope this helps
to measure charge in a battery, put the red cable cable into the DCV scale marked 0-20 - that will be accurate enough. Always start at the highest scale and work down you should never try to measure "out-of-scale".
Then you put the black cable to batter earth, the red to positive, and it will read the battery voltage.
Now, say you want to test that current is reaching, oh let's say the starter motor. leave the black cable on earth, and touch the red cable on the starter terminal. If you turn the starter over, the voltmeter should read the same as test 1 above, ie 12 volts or so.
ok so volts measures the difference in electrical charge between one thing and another, while they are connected.
DCA measures amperes - ie the current running THROUGH a cable at any time. it should be connected in series (ie remove the terminal and connect the meter BETWEEN the wire and component. In 20 years, I have never found a need to use this setting on mine, but I suppose it's useful for some things.
Ohms measures electrical resistance - DO NOT connect over live circuits. For example, you can check that a cable is not broken internally - connect the ohmmeter to each end of the cable, resistance should be zero or close to it. If there is a high resistance, might be a break or bad contact.
hope this helps
Make sure that it's in volt-reading mode instead of ammeter-mode when measuring a voltage, unless you like losing your eyebrows!
Google is your friend: www.google.co.uk/search?hl=en&q=using+a+multi-meter&meta=
Google is your friend: www.google.co.uk/search?hl=en&q=using+a+multi-meter&meta=
fid said:
For the battery I'd use any of the DCA's,
I know there are more detailed instructions if you follow the Google link, but:
DON'T PUT THE METER ACROSS THE BATTERY WHEN IT'S SET ON DCA - you'll get a burning smell and the meter will turn into a moulten mass, if you're lucky. If you're unlucky, the battery will blow up, and really you don't want do that.
The 20VDC setting is fine for car use.
I am an electrical engineer.
1) Set to Ohms to see if the bulb has a break (some meters also go beep)
2) Set to Volts to check voltage of battery 12v for car and if engine running and charging it is approx 13.8v
3) Set to Amps to see how much current an item is using, in this example we are using a bulb.
On this example by setting the meter to Volts you can use the meter to see if a wire is "live" ie reading 12volts connecting the black lead (-) to the car body (as common in 99.99999% of cars made) by turning the ignigtion on or off we can see if the cable is switched.
Another example (not shown) is a speaker cable, trace it back through the body work set the meter on Ohms and connecting one end and the other we should get a reading or "beep"
tvradict said:
Charge in a battery, if the Cables are intact in a wiring loom, and to see if there is current in a few cables in the shed.
Actually, that sounds like a Physics O-Level question! My reasoning is that you've chosen a scenario for each parameter: amps, volts and ohms.
A simple way to see if a wire is live mains is to use a mains tester screwdriver (these have a neon lamp inside). Place the tip on a live wire, then touch the top of the screwdriver. The resistance makes it perfectly safe to do this. If the neon glows, do not touch that wire!!
tvradict said:
I have a voltmeter and no Idea how to use it.......
Anyone offer any guidance?
Place the red lead and the black lead neatly in the side pouch of the multimeter. Pick up phone and dial the number of someone that does know how to use a multimeter.
That electrickery stuff can give you quite a startle if you go probing wires your unsure of.
Stuart,
The "charge" in a battery (lead acid) is best checked using an hydrometer to test the specific gravity of the electrolyte.
But battery "condition" can be checked using a voltmeter across the battery whilst switching a load on it (Headlights?). The voltage should hold up well under load. Many knackered batteries will give you a full voltage when not connected to anything.
On a car, do it across the terminals ON the battery, then recheck by moving the black to a good car chassis earth. This will show up a bad earth connection.
DC Amps on a multimeter is of limited value outside of "electronics" and a "clip-on ammeter" is usually used, (for DCA a "hall effect" one). this means that you don't need to break the circuit to check the current flowing in a wire.
For checking wiring you can either do a live check by using AC Volts or DC Volts depending what you're checking. Leave the Black probe on Neutral (mains) or Negative (car battery) and check through the circuit using the red probe until you find the point at which voltage is lost.
OR
Switch everything OFF, and use the 200 ohm range to check continuity of a single wire, some meters have an audible beeper for this (which is nice).
The "charge" in a battery (lead acid) is best checked using an hydrometer to test the specific gravity of the electrolyte.
But battery "condition" can be checked using a voltmeter across the battery whilst switching a load on it (Headlights?). The voltage should hold up well under load. Many knackered batteries will give you a full voltage when not connected to anything.
On a car, do it across the terminals ON the battery, then recheck by moving the black to a good car chassis earth. This will show up a bad earth connection.
DC Amps on a multimeter is of limited value outside of "electronics" and a "clip-on ammeter" is usually used, (for DCA a "hall effect" one). this means that you don't need to break the circuit to check the current flowing in a wire.
For checking wiring you can either do a live check by using AC Volts or DC Volts depending what you're checking. Leave the Black probe on Neutral (mains) or Negative (car battery) and check through the circuit using the red probe until you find the point at which voltage is lost.
OR
Switch everything OFF, and use the 200 ohm range to check continuity of a single wire, some meters have an audible beeper for this (which is nice).
Gassing Station | The Pie & Piston Archive | Top of Page | What's New | My Stuff