Digital Multimeters (How to use them)

[kyleservicetech]

Perhaps a few wattflyer readers have considered buying a Multimeter, but were concerned that they would not be able to use one of these very useful instruments effectively.

If you are in this catagory, take a look at the attached PDF file on those Digital Multimeters.

Perhaps you might find it useful or find something new in it

kyleservicetech (or dennisv)

[Rabbitcreekok]

Thanks, Kyle, that is a very nice link on meters and was very helpful.

[balsa1]

very good now I can do a little more than check voltage would welcome mor of this type of info. Thanks Les

[PaperAirplane]

Thanks a billion. So to test servo pull I would just hook up the esc to the reciever in one slot and make the banana plug thing with the servo extension in between the servo and a reciever slot?

[kyleservicetech]

Originally Posted by PaperAirplane

Thanks a billion. So to test servo pull I would just hook up the esc to the reciever in one slot and make the banana plug thing with the servo extension in between the servo and a reciever slot?

Yep, just take a standard "aileron extension" cable, (perhaps one that's been in a crash and is no longer trusted??) carefully cut the brown wire. Strip off about 3/4 inch of insulation from the two ends of the brown wire. I just use my fingernails, so as to not nick the wire strands. Double over the stranded wire so its now about 3/8 inch or so, and insert it into the banana jack. Then just tighten down the banana jacks locking screw and you're ready to go.

Just make certain you don't tighten down the locking screw over the insulation of the brown wire. :o

This modified cable can be used anywhere, from in between the receiver and a servo, to in between the battery and receiver, where it will show the receiver's battery drain, plus any servo's that might be plugged into the receiver.

[PaperAirplane]

So there is only one banana plug on the wire. I just want to make sure.

Thanks
PA

[kyleservicetech]

Originally Posted by PaperAirplane

So there is only one banana plug on the wire. I just want to make sure.

Thanks
PA

Nope, two bannana plugs, one for each end of the brown wire.

(Take a look at the attached photo) I've got the red and black bannana plugs arranged so that when its plugged into the respective connections on the multimeter, the meter shows minus milliampere currents for servo tests, and shows plus currents when connected between the charger and battery. To do this, plug in the battery, and connect the red binding post to the cut brown wire that leads to that battery. The black binding post connects to the other brown wire.

Nice thing about this test cable, it allows you to test anything connected to the cable. Like plugging it in between your receiver battery, and your wall charger, just to verify if your wall charger is actually charging at its 50 milliampere rate.

If you test any servo's with this cable, make certain your multimeter is on its 10 Amp range. Most meters under several hundred dollars have a range from 0-200 milliamperes, and 0-10 Amperes. Nothing in between. That 200 milliampere range is usually fused, and the current pulled by just about any servo may blow it.

My Fluke 87V meter does have a 0-2 Amp (0-2000 Milliampere) range on it.

Have a good day!

[PaperAirplane]

Thanks man. I went back to the article after I posted yesterday and got a better idea, but you just made it perfectly clear.

Will go pick up the banana plugs asap.

[PaperAirplane]

I can remember which thread I was posting updates on, so Ill post here.

Anyways, I make the extension wire hookup (finally) and I will get some measurements ASAP. So far, I remember hooking up the good servo to the rx with the multimeter inbetween, setting it at 20 volts. The servo wouldnt move, but I got a measurement of 3.08. That was a tester. Is that the correct voltage?

PA

[kyleservicetech]

Originally Posted by PaperAirplane

I can remember which thread I was posting updates on, so Ill post here.

Anyways, I make the extension wire hookup (finally) and I will get some measurements ASAP. So far, I remember hooking up the good servo to the rx with the multimeter inbetween, setting it at 20 volts. The servo wouldnt move, but I got a measurement of 3.08. That was a tester. Is that the correct voltage?

PA

Hi, if you have your multimeter in series with the servo with that banana plug setup, the multimeter must be set it up on the 10 Ampere range, for DC current. (If you have the meter set up for voltage while trying to measure Servo current, you've got an open circuit, and the servo won't move.)

If your meter shows pretty low currents on its 10 Ampere DC range, change to the 200 Milliampere DC range. Be careful of the 200 Milliampere range though, if you stall the servo, the high currents pulled will blow the meters internal fuse.

[PaperAirplane]

Sure, will do!

I think I did a decent soldering job, so everything should be set.

Just forgot to put the plastic casing on before soldering the wires into the connectors

DOH!

PA

[kyleservicetech]

Originally Posted by PaperAirplane

Sure, will do!

I think I did a decent soldering job, so everything should be set.

Just forgot to put the plastic casing on before soldering the wires into the connectors

DOH!

PA

Boy, in my 50 years of soldering amphenol connectors with 19 pins and up, all it takes is once to forget to put the shell on the cable first, and have to unsolder and do it all over again. And' I've done it.

I traveled to Texas some years ago on a field trip to fix our equipment. Found the local service guys cut our connector off, stuffed the cable into conduit, and resoldered all 24 pins of that amphenol connector.

Their soldering equipment? A blow torch!! Melted the insulation off of all the wires. I was there til 3 AM fixing that one.

[Turner]

I'm looking at the article, page seven. What does it mean when you talk about the servos tracking each other?

[kyleservicetech]

Originally Posted by Turner

I'm looking at the article, page seven. What does it mean when you talk about the servos tracking each other?

Good question.

That only applies when you've got multiple servos on one function. Like one of our club members has four (yes four) high torque servos on just the rudder of his monster plane. The model uses a 200 cc twin cylinder engine. The rudder alone of that 3D plane has more area than the wings of a lot of the smaller electric models we fly.

If these four servos do not accurately track each other, they can fight each other, resulting in many problems.

[Turner]

Okay, I understand. Thanks.

And thanks for the article. I've been wondering for some time if this was all it might take to test the system draw.

[kyleservicetech]

Originally Posted by Turner

Okay, I understand. Thanks.

And thanks for the article. I've been wondering for some time if this was all it might take to test the system draw.

Yup, its quite simple (Once you know how )