Measuring amps?

[DadHav]

Hello, Recently I saw a picture of someone measuring the amp draw of a brushless, using a clamp over meter. Can this be done? Would you have to measure over the battery or the motor wires? I couldn't tell from the picture. I wonder if there might be a probe that could plug into your DVM as an attachment? This would be a kewl way to do this without having additional wires to help drop your voltage. No, Yes?

C YA

[*Crash*Johnson*]

I've worked in garages as a mechanic, and we used to have an attachment to the DMM (digital multimeter) that measured amp's through a wire like that. Makes it easier to check current without breaking the circuit.

With my motors I usually use my DMM like such:

Run batt + to the ESC.

Neg - to the DMM neg and the DMM pos + goes to the ESC neg.

essentially putting the DMM "inline" of the battery. My DMM will measure up to 20A in burst, so you'll have to make sure yours will do that to hook it up like this.

[Pipistrelli]

Run a search on 'clamp meter' on ebay and see what comes up! :lol:

[*Crash*Johnson*]

Took your advice Pip and seen them. 10 bucks!?!?!?! sweet!

Makes current checking much easier!

Only question: they say ACA - 1000 amps. Will they display DC Amps??

[DadHav]

Thank's Pip, Crash, The meters that I saw on E-Bay were mostly AC only. The few that could measure DC were closer to the $100.00 range and weren't close to closing bids yet. I guess I'll just keep hooking up parrallel to my DVM until I can barrow a meter to see if I want to make that investment.

C YA

[Pipistrelli]

Because the clamp meter works on inductance it will measure AC amps directly.

However, for DC amps you will get an EMF reading in volts than can be translated into amps, one one I've seen the reading is 70mV which equates directly to 7.0A!

I have an electrical engineer friend and will confirm this is correct with him.

[DadHav]

Pip, Crash, or anyone, I broke down and bought a clamp meter. I needed a replacement for an older meter that got caught in a flood. Anyway: I paid $149 for the unit from Granger Industrial Supply. It seams to measure amps very nicely by just slipping the clamp over one of the battery leads. Auto ranging is from 0-40 and 0-400 amps DC or AC. The resolution is good enogh that it measures milliamps. I'm happy.

C YA

[Roy_Oetting]

Hi, I use the astroflight micro meter. It gives amps volts and watts all at one time. It's easy to hook up. Just hook the battery to the meter, then hook up the other end to the speed control. They make a bigger one if you use a lot of power. I couldn't give you the page for some reason but look under chargers.

http://www.astroflight.com

[DadHav]

Yep, You're right again Roy. That is a good meter that you are talking about. I just like to be able to clamp the meter around a wire without any extra connections or length of wire. After that it's not to hard to figger out the rest. My math has always been gooder than my English anyhow.

C YA

[Roy_Oetting]

DadHav, Your always going to hook up a battery or power source. When using the Watt meter or Micro meter you hook up the battery to the meter and then you connect the meter to the speed control, and your in business.
You do have to hook the meter to the battery or power supply first so it calibrates. For those who are not familar with the Micro Meter I've enclosed a picture. You may be able to read the meter . On the left side is amps and watts and on the right side is volts and amp hours.The extra connector on the meter I added because the circuitry in the meter needs 4.8 volts to opperate so if you were just doing one LiPoly the meter wouldn't turn on. So for low voltages I can hook up and run the meter with an external source.
Roy

[LBMiller5]

In this thread, I go through a pretty in-depth discussion on current in motors, and give instructions on how to build a simple current shunt to measure o-10 or 0-100 amps of current for under $10.00 in parts. (Even less if you already have some extra connectors.)

Check it out here:

http://www.gobrushless.com/forum/viewtopic.php?t=288&postdays=0&postorder=asc&start=0