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sherman89 04-01-2014 02:33 PM

watt meter
 
Can anyone tell me who manufactures a 160-200 amp watt meter?

rcers 04-01-2014 03:03 PM

Quote:

Originally Posted by sherman89 (Post 944229)
Can anyone tell me who manufactures a 160-200 amp watt meter?

You will need a shunt type, or better a clamp type for that many amps. In-line will start to fry stuff...

Sears makes a good clamp meter....

Make SURE the clamp meter is both AC and DC.... :)

http://www.sears.com/extech-400a-ac-...p-03416274000P

Mike

kyleservicetech 04-01-2014 07:34 PM

Quote:

Originally Posted by sherman89 (Post 944229)
Can anyone tell me who manufactures a 160-200 amp watt meter?

Check out this unit, also from Sears. It is a multi-function meter with thermocouple thermometer, volts, resistance, and clamp on Amps. Most Sears stores have it in stock.

http://www.sears.com/craftsman-digit...p-03482369000P

I've got one, and several club members also have one. I've checked it against my $$$$ Fluke 87V meter with a 100 Amp 1% precision shunt. That Sears meter is pretty close in accuracy.

Note that most clamp on ammeters such as the Harbor Freight units are AC only, not useful for our electric models.

So, with this meter, with its DC current ranges of 0-40 Amps, and 0-400 Amps, with a second volt meter, you can quickly calculate watts. Just power up the motor, measure Amps, and Volts with the second meter while the motor is pulling full power. If you measure 400 Amps on your model, with a 14S LiPo battery, thats about 20,000 watts, which should pretty much cover everything.

The formula is Watts equals Volts Times Amps, so if you have 21 Volts at 74 Amps, that's 1554 watts. At 746 Watts per horse power, that's two horsepower.

(FYI, the starter in your car draws around 120-150 Amps at 12 Volts DC)

sherman89 04-01-2014 10:30 PM

Question, I not an electrician------how do I use it-----do I loop all 3 wires or go it them one at a time? Any suggestions?

kyleservicetech 04-01-2014 11:57 PM

Quote:

Originally Posted by sherman89 (Post 944292)
Question, I not an electrician------how do I use it-----do I loop all 3 wires or go it them one at a time? Any suggestions?

These type meters have a spring loaded jaw. First, turn on the meter, and set it to read either 40 or 400 Amps DC (Direct Current) current. If you should over-range your meter on 40 Amps, just reset your meter to read 400 Amps DC. Then, hit the "zero" button so the meter shows zero current. Then, clamp the jaws around ONE of the battery leads. Fire up the motor, and simply read the current pulled directly on your meter. Nice, you don't need any cable adapters on these clamp on meters.

If you have your meter set to read AC (Alternating Current) current on the battery, you might get a few strange readings, or perhaps no reading at all. Just won't work.

If you want to calculate watts, you will need a second meter to measure the voltage on your battery pack while running the motor. Even a cheap Harbor Freight $4.00 meter will do just fine for voltage measuring.

And, as indicated, watts equals volts times amps.

FYI, in theory, you could read the current INTO the motor by clamping around one of the three motor leads. Yes, the motor current IS AC (Alternating Current), but its frequency is likely out of the ability of the Sears Clamp on meter to read it.

It takes 5 minutes to explain how to use one of these meters, and about 5 seconds to actually read current with one.

These meters can be used to measure ANY current, even that pulled by your house hold appliances. Just remember that these meters must clamp around ONE of the two leads. If you clamp around both leads inside the power cord of your vacuum cleaner, for example, it will read zero AC current. The current in both wires inside your appliance are in different directions, and they cancel out. An easy way to make an adapter cable for this purpose is to take a cheap lamp cord type extension cord, split the two wires apart for a few inches in the middle of the cord. Then put your clamp on ammeter around ONE of the two wires in the extension cord while set to AC current. Plug in the extension cord, and plug in your vacuum cleaner to the other end.

sherman89 04-02-2014 01:34 PM

Quote:

Originally Posted by kyleservicetech (Post 944295)
These type meters have a spring loaded jaw. First, turn on the meter, and set it to read either 40 or 400 Amps DC (Direct Current) current. If you should over-range your meter on 40 Amps, just reset your meter to read 400 Amps DC. Then, hit the "zero" button so the meter shows zero current. Then, clamp the jaws around ONE of the battery leads. Fire up the motor, and simply read the current pulled directly on your meter. Nice, you don't need any cable adapters on these clamp on meters.

If you have your meter set to read AC (Alternating Current) current on the battery, you might get a few strange readings, or perhaps no reading at all. Just won't work.

If you want to calculate watts, you will need a second meter to measure the voltage on your battery pack while running the motor. Even a cheap Harbor Freight $4.00 meter will do just fine for voltage measuring.

And, as indicated, watts equals volts times amps.

FYI, in theory, you could read the current INTO the motor by clamping around one of the three motor leads. Yes, the motor current IS AC (Alternating Current), but its frequency is likely out of the ability of the Sears Clamp on meter to read it.

It takes 5 minutes to explain how to use one of these meters, and about 5 seconds to actually read current with one.

These meters can be used to measure ANY current, even that pulled by your house hold appliances. Just remember that these meters must clamp around ONE of the two leads. If you clamp around both leads inside the power cord of your vacuum cleaner, for example, it will read zero AC current. The current in both wires inside your appliance are in different directions, and they cancel out. An easy way to make an adapter cable for this purpose is to take a cheap lamp cord type extension cord, split the two wires apart for a few inches in the middle of the cord. Then put your clamp on ammeter around ONE of the two wires in the extension cord while set to AC current. Plug in the extension cord, and plug in your vacuum cleaner to the other end.


Thanks so much for the info.

hayofstacks 04-02-2014 10:58 PM

I used to have a nice fluke meter when i spliced cable. it got jacked from my work truck. ill get another one, one day.

sherman89 04-03-2014 09:01 PM

I found out thatCC does logging and after downloading the log info all is good.

fhhuber 04-03-2014 11:32 PM

Depends on the ESC... some do have logging capability. Most do not.

Rodneh 04-04-2014 05:51 PM

Quote:

Originally Posted by sherman89 (Post 944292)
Question, I not an electrician------how do I use it-----do I loop all 3 wires or go it them one at a time? Any suggestions?

You measure by clamping around either the black lead only or the red lead only on the wires between the ESC and the battery (only two leads there). You do not measure one of the leads between the ESC and the motor as that is a pulsating DC current which will not provide a reliable or meaningful reading on the clamp on meter.

fhhuber 04-04-2014 06:22 PM

Isn't the current between the battery and the ESC also DC that is pulsing? (3X as fast as any one wire between ESC and motor)

The current in a single lead between ESC and motor won't equal the current between the battery and ESC. You could measure it with the clamp-on meter though. Someone could probably come up with the correct number to multiply by to know what the total is for the motor.

kyleservicetech 04-04-2014 10:48 PM

4 Attachment(s)
Quote:

Originally Posted by fhhuber (Post 944507)
Isn't the current between the battery and the ESC also DC that is pulsing? (3X as fast as any one wire between ESC and motor)

The current in a single lead between ESC and motor won't equal the current between the battery and ESC. You could measure it with the clamp-on meter though. Someone could probably come up with the correct number to multiply by to know what the total is for the motor.

I don't think the AC current in a single lead between the ESC and motor will be anywhere close to the DC current between the ESC and battery. Problem is, the ESC-Battery is DC. The current between the ESC and motor is high frequency AC or Alternating Current. Most Clamp On Ammeters don't work well at high frequency.

FYI, these brushless motors are actually three phase AC motors with a variable AC (Alternating Current) frequency drive, namely the ESC itself.

Take a look at the attached JPG's from my oscilloscope that shows a brushless motor's AC voltage at full power on one phase. Then running that motor at reduced power.

The third and fourth JPG's show my setup with a Hacker motor, and the resulting three phase AC voltage that comes from the motor. The microcontroller circuit is something I came up with to allow watching three signals out of the motor on one oscilloscope channel.

kyleservicetech 04-05-2014 01:22 AM

Quote:

Originally Posted by hayofstacks (Post 944391)
I used to have a nice fluke meter when i spliced cable. it got jacked from my work truck. ill get another one, one day.

If you're after accuracy, just about any digital multimeter worth perhaps over $20 or so would do a good job.

If you want to be able to drop your meter 10 feet to a concrete slab, you need a Fluke. (Yeah, I did that once to an 87V meter in a high voltage substation. Didn't even affect it.)

hayofstacks 04-05-2014 03:49 AM

Quote:

Originally Posted by kyleservicetech (Post 944532)
If you're after accuracy, just about any digital multimeter worth perhaps over $20 or so would do a good job.

If you want to be able to drop your meter 10 feet to a concrete slab, you need a Fluke. (Yeah, I did that once to an 87V meter in a high voltage substation. Didn't even affect it.)

Which did happen more then you might think ;).

http://i33.photobucket.com/albums/d8...2010.37.07.jpg

kyleservicetech 04-05-2014 05:46 AM

Quote:

Originally Posted by hayofstacks (Post 944539)
Which did happen more then you might think ;).

That reminds me of a story one of our customers at work told a few years back. The utility was looking to buy a whole bunch of digital meters for their crews, and was receiving sales pitches from various suppliers.

The Fluke rep came in, asked for the purchasing agent. After meeting him, he took a brand new Fluke meter out of its box, pitched it against a concrete wall. Then told the purchasing agent to have his standards guys check out the meter.

He said he'd be back in a week to pick up the meter, and walked out the door. That was the entire sales pitch.

Guess which meter the utility purchased?

Doubt if they still do that though in this day and age. :cool:

fhhuber 04-05-2014 07:19 AM

I'm seeing some 130 amp 60 v wattmeters (all look like the same one with different labels)... anyone actually push one of them near their limit?

http://www.headsuphobby.com/GT-POWER...eter-F-130.htm

Hobby king's looks exactly the same except Turnigy label.

Its about time I got a pic for my 5Kw "badge" here. I burned up an Astro-Flight 100 amp 50 volt rated wattmeter.

AEAJR 04-05-2014 04:41 PM

Quote:

Originally Posted by sherman89 (Post 944229)
Can anyone tell me who manufactures a 160-200 amp watt meter?

I don't think it says here. What are you running that is drawing that kind of current? Our models rarely draw more than 100 amps, and 70 or less is far more common.

fhhuber 04-05-2014 05:20 PM

I have a pair of EDFs that with the current ESCs are rated 100 amps (each) on 12S (they pull 105 amps peak) Others have just dropped in 18S LiPo without changing anything and had no problems...
When these EDFs were made the 100 amp 12S rated ESC was the biggest available. The motors are rated for the 18S continuous full throttle.
(spinning the fan above 80% on 12S just "stalls" the fan if the airplane can't get up to speed to give the EDF enough "ram air" to keep up...)

sherman89 04-05-2014 10:54 PM

Quote:

Originally Posted by AEAJR (Post 944604)
I don't think it says here. What are you running that is drawing that kind of current? Our models rarely draw more than 100 amps, and 70 or less is far more common.

I have a Spitfire powered by a RIMFIRE 50cc motor on 12s through a CC 160 amp esc turning a Biela 22x10-2. After checking the log from the esc max amps is159.3, max watts is 6565, max vts is 49.9. Until I loaded the logs I had no idea what was causing the lipos to heat up. Now I know.

kyleservicetech 04-05-2014 10:56 PM

Quote:

Originally Posted by AEAJR (Post 944604)
I don't think it says here. What are you running that is drawing that kind of current? Our models rarely draw more than 100 amps, and 70 or less is far more common.

Yeah
A club member had a pair of ducted fans supposedly rated for a 6S LiPo battery. I ran them up, found with my Craftsman #82369 digital AC and DC clamp on ammeter that those fans were pulling 175 Amps. Each.

The motors never got hot, but the club member was using a pair of 100 Amp Castle creations ESC on both fans. The jet model took off with authority, but two minutes into the flight, both ESC's got over 200F and shut down.

An off the field landing pretty much destroyed the model.


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