Testing New Multimeter-What to Measure

You'all should maybe have fun with this one.  I got a multimeter as it seems that the advice for  every furnace, fridge, and water heater hiccup begins with using one.  So I got this one from Amazon but with $12 off cause there is a newer model.

https://www.amazon.com/gp/product/B06WVS96XC/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Measures a.c. and dc volts and amps, resistance, continuity, and has a separate probe for temperature-- mostly auto range finding.

Now I need some things to Measure so I can test it-- besides sticking the leads into a ac  120 v household outlet.  BTW if i do stick leads into a normal outlet and try to measure amps, is there a value im looking for or is it gonna be the breaker value for that circuit?

Can you give me some ideas of what else to measure?  I can disassemble something if needed- what would a AA battery voltage be? Assuming it can be measured.  Help with the learning curve appreciated.

My "cute "star wars generator arrived and I love, love it.  I can lift it too -- one-handed, so it looks like with a little  effort all should be good. 

Linda

Did the meter come with an instruction sheet? If so, please take the time to read through it and understand each function, then ask us on the stuff that doesn't make sense. That would be a lot better for you and us. Not trying to be unfriendly here, just can't get the right words out so I don't sound so. You can't stick the leads into a 120 volt outlet and read amps. A "AA" battery should read about 1 1/2 volts DC.

Amps have to be measured across a load.  No load no amps.  You can measure DC volts by placing the leads on the battery posts.  With the power shut off and one lead disconnected you could measure ohms across the water heater electric element.

To measure voltage (AC or DC) the meter's test probes go across the source of the voltage.  Either into the AC socket (AC volts) or across the battery terminals (DC volts).  Same thing if you want to see if something's receiving voltage - red probe goes on the hot wire,  black on the negative wire or ground.

Dry cell batteries like AA cells, etc. will read somewhere around 1.5 to 1.6 volts when new, then their voltage will degrade as they're used up.  Anything below about 1.2 volts is essentially dead.

Resistance (ohms) is only used on unpowered circuits.  When you switch to Ohms the display will indicate OL (overload or no continuity).  Touch the probes together and the meter will read continuity, or zero ohms.

Most things are somewhere in between, as it's resistance that limits current flow.  Take a light bulb out of a socket and measure the resistance across the base pins.  A good bulb will give some kind of resistance reading, one that doesn't (OL) is open, or burned out.

Current measurement is a special case.  Voltage is electrical pressure, so you measure it by placing the meter across the voltage source.  Current is measuring the quantity of electrons flowing through the circuit.

When you measure current (Amps or ma, milliamps) the meter becomes a short circuit between the probes, so electricity can flow from one probe to the other, letting you measure the amount of current the device is using.  You DON'T want to put the meter across an AC outlet or across a battery in current mode.

To measure current, you place the meter in line with the thing you want to measure, not across the wires feeding it.  Disconnect one wire and connect it to one meter probe, then place the other probe on the point you removed the wire from.  This lets the current flow through the meter so it can measure it.

For most measurements around the RV you'll move the red wire to the 10 Amp socket and select that range, but the lower current ranges (ua and ma or micro- and milli- amp) use the same socket as the voltage and resistance ranges.  Be careful that the meter is on a voltage range, not resistance or current, when you're measuring voltages.

In fact, it's  good idea to set the range you want first, then connect the meter.  If you have to change ranges, disconnect the meter, change the range and then reconnect it.

To use the example of measuring the electric water heater element, you can see if it's receiving voltage (120 volts AC) by putting the meter into AC Volts mode and putting the probes on both terminals feeding it with the power on.  Or the resistance (ohms) of the heating element turning the power off (power MUST be off when making resistance measurements!) and again putting tne meter across the element's terminals.  Disconnect one of the power wires so you only measure the resistance of the element.

You could also measure how much current the element draws by putting the meter on the 10A range, moving the red lead to the 10 A socket and connecting the meter between the wire you removed and the terminal it was connected to.  But in this case we know the water heater draws more than 10 amps, so trying to do this measurement will damage the meter.

One thing you can measure is the voltage of a fresh Carbon-Zinc flashlight battery (Like was common in say 1960) Alas I do not have the manual handy with the proper voltage (it is not 1.5) but ... hold on  Open circuit for a fresh Carbon-Zinc Battery per the manual for my old Vacuum Tube Volt meter (no longer in existance) is 1.55 volts

Lou -- Thank you for the examples, just perfect.  Got 1.518 V on couple AAs and 1.58 on a size C.  Various light bulbs gave 22, 47 and 73 ohms.  Got 000.1 on the resistance when touching the leads together.  When measuring resistance, it takes a minute or so for the meter to settle down to a steady reading.  I assume this is normal? 

I already had a kill-a-watt, so between the two, I should have the basic diagnostics covered I hope.

I did YouTube to learn about types of meters and various functions, so I think I'll go back and watch more on actual ops, and see more examples maybe.  So many of them dealt with electronics however i.e. building circuit boards -- which I don't have available.

Thanks again
L

Linda,

Lou pretty well wrote what I was thinking.  A couple additions, which he hinted at.

When measuring Ohms, there should be an adjustment on the meter.  Set to the desired range, then touch the probes.  Adjust the meter to read -0-, then measure.

One way to measure amps is go to the battery and disconnect one side - either side.  With the meter properly set, touch the correct probe to the disconnected battery terminal and the other probe to the wire you disconnected.  The meter "replaces" a section of wire, and it measures the current flow through the meter.  In this case, it reads total load on the battery.

Wise move learning how to use it now!  You will have future need!

grashley said:

When measuring Ohms, there should be an adjustment on the meter.  Set to the desired range, then touch the probes.  Adjust the meter to read -0-, then measure.

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You're thinking of the old analog meters. Gordon..  There isn't any zero Ohms adjustment on the new digital ones. 

Measure Amps with care.  Your meter is effectively an expensive fuse when in the Amps mode.  DO NOT try to measure across an AC outlet, for example, while in the Amp mode.  The fuse will blow.  Now some meters have a user replaceable fuse and some don't.  Most cheaper ones don't, so you just have to buy a new meter.  Also, don't try to measure resistance (Ohms) when power is applied because...well, just don't.  Other than that, experiment to your heart's content.

Dreamsend said:

When measuring resistance, it takes a minute or so for the meter to settle down to a steady reading.  I assume this is normal? 

...

Thanks again
L

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You're welcome, Linda and have fun with your meter!

It's normal for a digital meter to take a couple of seconds to stabliize when measuring resistance.  There's such a wide range of possible resistances that on an old analog meter, you'd manually select a range, then see where the meter needle stopped rising.  If you guessed wrong, you'd change the range and try again. 

The digital meter does much the same thing automatically, so it takes a moment or two for it to decide what range to use before it can display the result.

It's time to go open the hood of your truck and measure the battery voltage.

Do it once with the engine off and then do it with the engine running. The voltage will be higher with the engine running.

Tell us why it is higher with the engine running.

That 1.55 volts is for CARBON ZINC, Alkaline may be different,,, back then teh manual I refereenced was printed. Alkline were not common. Just so you know. 

I actually know how to lab-calibrate a volt meter but.. Few places (outside of a pnysics or electronics lab) have the needed hardware.

Arch Hoagland said:

The voltage will be higher with the engine running. Tell us why it is higher with the engine running.

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Hi Arch. -- Ah, a teaching moment.  Could it be because the alternator has taken over the electrical system and the battery is like no longer in play?  The alternator is at a higher voltage than the battery at rest, because it has to charge the battery after the battery has lost charge due to start-up.  Sorry, I'm not very sophisticated at mechanical language.  Am I close? 

And Molaker- Thank you for the safety and operating reminders.  Reading directions stated in several ways really helps plant it in what grey matter I have left.  The meter has a replaceable fuse, but . . Rather not have to mess with replacing due to operator error. 

Think I've gotten the hang of things and everyone's help is much appreciated.

L

You get an A !!

Technically, the battery is still part of the circuit, but it is now receiving amps from the alternator, not supplying them.

Any time you are trying to troubleshoot any problem you are trying to find what you are missing so, you have to know what to expect at any given point. Any test is useless if you don't have values. The Amp measurement for your meter is limited to 600ma which is a very small number. A starter motor may use as high as 500 amps initially some even higher on a diesel engine.

Having taught auto mech for 20 years, I found that trying to teach students to use their meter was a real challenge especially when they need to understand electricity fundamentals (Ohm's Law)_ and the relationships that take place in the circuit under varying conditions. There are some good auto text books for learning the 12v system and then you also need to understand the  alternating current house part of the circuitry. Where do you want to start? As someone mentioned in an earlier post, start by opening the hood and measuring volts at different points and then see what changes take place when you activate and deactivate a system.

Ask any electrician which way electricity flows and you will hear of a least 3 theory's and the best one I have heard is we don't know because we can't see those little atoms. The nice thing about this forum is that many are willing to give you values that you should have when everything is present and in some cases take the information you give and give you a fairly fair assessment of your problem.

This may not sound encouraging but you basically need an engineering degree and in the case of an RV, you deed both alternating current and direct current understanding. Good luck on learning that simple little meter but it can be done. ASE certified mechanics certified in electrical normally spend 6 months just getting the basics of electricity in school and a lifetime getting practical experience and shortly find out that they can make more money in a different field like communications.

Dreamsend said:

Hi Arch. -- Ah, a teaching moment.  Could it be because the alternator has taken over the electrical system and the battery is like no longer in play?  The alternator is at a higher voltage than the battery at rest, because it has to charge the battery after the battery has lost charge due to start-up.  Sorry, I'm not very sophisticated at mechanical language.  Am I close? 

And Molaker- Thank you for the safety and operating reminders.  Reading directions stated in several ways really helps plant it in what grey matter I have left.  The meter has a replaceable fuse, but . . Rather not have to mess with replacing due to operator error. 

Think I've gotten the hang of things and everyone's help is much appreciated.

L

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Close enough for government work.  Have you actually gone and done it yet?    Get crackin' girl!!!

You need the practice to reinforce your new knowledge.  Electronics classes always had theory in the morning and lab in the afternoon.

gwcowgill said:

There are some good auto text books for learning the 12v system and then you also need to understand the  alternating current house part of the circuitry. Where do you want to start? As someone mentioned in an earlier post, start by opening the hood and measuring volts at different points and then see what changes take place when you activate and deactivate a system.

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If you can remember the names of the books, please post.  There are a few things I'd like to be able to do.  But I'm trying to avoid being shocked into the afterlife as I do them. 

garyb1st said:

 

If you can remember the names of the books, please post.  There are a few things I'd like to be able to do.  But I'm trying to avoid being shocked into the afterlife as I do them. 

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Here's one I picked from Amazon.  I'm not necessarily recommending this particular one, but if you are an Amazon Prime member, the price is right.  There are lots and lots of others available there.

Thanks Tom. 

Linda, I owe you a very big apology. You took it upon yourself to buy a piece of equipment and are taking it upon yourself to learn to work on your RV. You came here and asked a valid question, and I gave you a really lame reply. I've got excuses I could list, but excuses aren't a reason to do what I did. Again I apologize, and I thank Lou and the others for actually giving you some real help.