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Electric Ducted Fan Jets Discuss electric ducted fan jets here including setup tips, power systems, flying techniques, etc.

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Old 11-12-2014, 12:07 AM   #1
Suprawill1
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Default Watt Meter - Your Thoughts

Hi All,
Wondered if anyone has any experience with or seen reviews on these two.


This one looks pretty identical to the Turnigy, same casing and bare input/output wires but is 150A capable to Turnigy's 130A but $6 cheaper.

http://www.ebay.com/itm/FT08-RC-150A...-/141413493299



This one is only 100A Capable but I don't think I'll draw any more than that even with an upgrade in my 70mm F-16. What I like about it is that it has deans connector input/output jacks which is my exact set-up and has 6S balancing. It also has 3 selector switches that I don't see on most lower priced models.

http://www.ebay.com/itm/Digital-60V-...-/310887662046


I'm leaning towards the 100A one for said reasons and also cheaper unless someone has heard anything bad about it. Both shipped from the US.
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Old 11-12-2014, 12:27 AM   #2
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The second one is same as most use and has the facility to display cell values as well as having the balance function.

But beware - the balance function will be extremely slow

First one may look snazzy - but is limited in use.

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Old 11-12-2014, 01:06 AM   #3
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Well anything over 80 amps or so isn't really necessary. The reason is simple. When you get to these high amps you really should not use an in-line meter anymore. You really need a shunt or clamp meter for 100+ amps. Using inline can be really tough on the ESC due to the added wire length.

I still have my old original Astro meter so I comment on these. I personally would not test 130 amps inline.

Mike
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Old 11-12-2014, 01:21 AM   #4
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Got my watt meter from HeadsUpRC - readout is watts, volts, amps. 130 amp, add your own connectors, I used Deans T plugs since my stuff is not huge power. $33 = $2 shipping.
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Old 11-12-2014, 02:33 AM   #5
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Thanks for the hits! So it seems like I'll lean toward my first choice. Can't beat that functionality for 15.40 shipped!

Solentlife, I don't mind a slow balance function just as long as it is accurate.
In slow, do you mean it will take a while for the individual cell readout value to come up? Or am I missing something else?
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Old 11-12-2014, 03:43 AM   #6
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Originally Posted by Suprawill1 View Post
Hi All,
This one is only 100A Capable but I don't think I'll draw any more than that even with an upgrade in my 70mm F-16. What I like about it is that it has deans connector input/output jacks which is my exact set-up and has 6S balancing. It also has 3 selector switches that I don't see on most lower priced models.

I'm leaning towards the 100A one for said reasons and also cheaper unless someone has heard anything bad about it. Both shipped from the US.
Yeah
If you're planning on measuring over 100 Amps on a regular basis, IMHO, you're better off with a clamp on ammeter. Note that most clamp on meters are AC only, not useful for our DC battery powered models.

Sears Craftsman has an AC And DC clamp on ammeter for $60.00. Every so often, they've got it on sale for $54.

Using a clamp on ammeter is simple, just open the meters "jaws" and clamp it around just one of the two battery leads. Don't need any adaptor plugs or anything, just clamp it on.

This meter has two DC current ranges, 0-40 Amps, and 0-400 Amps. That will cover everything from a 100 Watt model, to the biggest available Hacker A200 motor.

I just used it a few weeks ago to check out the alternator ampere output on my Grand Caravan. With everything on, the Alternator was putting out 95 Amps. The starter on my Chev S10 pulls about 140 Amps.

This meter also has voltage, resistance, frequency, and even includes a thermocouple type temperature probe.

http://www.sears.com/craftsman-digit...adCell=REC_1_0

I've also got an Astroflight Whattmeter, but this clamp on ammeter is used far more often.

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Old 11-12-2014, 04:29 AM   #7
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Originally Posted by kyleservicetech View Post
Yeah
If you're planning on measuring over 100 Amps on a regular basis, IMHO, you're better off with a clamp on ammeter. Note that most clamp on meters are AC only, not useful for our DC battery powered models.

Sears Craftsman has an AC And DC clamp on ammeter for $60.00. Every so often, they've got it on sale for $54.

Using a clamp on ammeter is simple, just open the meters "jaws" and clamp it around just one of the two battery leads. Don't need any adaptor plugs or anything, just clamp it on.

This meter has two DC current ranges, 0-40 Amps, and 0-400 Amps. That will cover everything from a 100 Watt model, to the biggest available Hacker A200 motor.

I just used it a few weeks ago to check out the alternator ampere output on my Grand Caravan. With everything on, the Alternator was putting out 95 Amps. The starter on my Chev S10 pulls about 140 Amps.

This meter also has voltage, resistance, frequency, and even includes a thermocouple type temperature probe.

http://www.sears.com/craftsman-digit...adCell=REC_1_0

I've also got an Astroflight Whattmeter, but this clamp on ammeter is used far more often.
Thanks for the link on that Kyle! (hope that's your name)
If I graduate to the big boys, I'll certainly look this up. I don't expect to be pulling any more than about 70A with the upgrades but right now, I'm running stock with a more robust battery than it called for.

Stock:
FW 70mm F-16
2850KV outie 6 blade
45A ESC
HV Bolt 4S 2800mah 65C

Upgrade:
9 blade Wemo
3400KV HET outie
100A ESC
HV Bolt 4S 2800mah 65C
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Old 11-12-2014, 04:47 AM   #8
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Speaking of clamp-on ammeters, the price is right on this one if you don't mind going to China and all the specs are ok.

http://www.ebay.com/itm/DM6266-Digit...#ht_8411wt_924
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Old 11-12-2014, 04:55 AM   #9
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Originally Posted by Suprawill1 View Post
Speaking of clamp-on ammeters, the price is right on this one if you don't mind going to China and all the specs are ok.

http://www.ebay.com/itm/DM6266-Digit...#ht_8411wt_924
That looks to be AC Amps only. We need DC Amps for our stuff!

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Old 11-12-2014, 05:01 AM   #10
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Originally Posted by kyleservicetech View Post
That looks to be AC Amps only. We need DC Amps for our stuff!
Yeah, I wasn't sure because it seemed to measure ac & dc volts, why not dc amps too! lol
Back to school!
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Old 11-12-2014, 05:56 AM   #11
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Originally Posted by Suprawill1 View Post
Yeah, I wasn't sure because it seemed to measure ac & dc volts, why not dc amps too! lol
Back to school!
Yup, I looked up DM6266 in google, its AC amps only.

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Old 11-12-2014, 06:02 AM   #12
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Originally Posted by kyleservicetech View Post
Yup, I looked up DM6266 in google, its AC amps only.
What a tease!
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Old 11-12-2014, 06:11 PM   #13
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Originally Posted by Suprawill1 View Post
Thanks for the hits! So it seems like I'll lean toward my first choice. Can't beat that functionality for 15.40 shipped!

Solentlife, I don't mind a slow balance function just as long as it is accurate.
In slow, do you mean it will take a while for the individual cell readout value to come up? Or am I missing something else?
It will take forever and a day to balance out cells on a LiPo ... the rate it works at is VERY VERY low ...

Its better to do a balanced storage charge on a charger ...

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Old 11-12-2014, 07:04 PM   #14
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Originally Posted by solentlife View Post
It will take forever and a day to balance out cells on a LiPo ... the rate it works at is VERY VERY low ...

Its better to do a balanced storage charge on a charger ...

Nigel
Thanks Nigel! I have the Reaktor 300 for balance charging. I thought maybe the balance application on this watt meter was just for a balanced individual cell amp/voltage reading.
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Old 11-12-2014, 08:19 PM   #15
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Just how does a clamp-on DC amp-meter work?
I was taught that it took a pulsating or alternating current in a wire which creates a varying magnetic field around the wire to induce a voltage in another wire.

This is how a common transformer works.

If it responds to pulsating DC current, does it give us the; average current, RMS current, or peak current ? What does the readout of a standard wattmeter display ?

I had a CC PH 25 ESC getting very hot very quickly, even though my Astro wattmeter showed only 2 amps ( this was a small formed can motor, <50 grams ) this would happen at low throttle, at high throttle, the speed control would cool off.
Castle engineers told me I had a "high wind" motor which created a condition that would require an oscilloscope to determine the actual amperage going through the ESC.

That problem told me, sometimes our instruments can play tricks on us.
I have not had any other motor do this. I did not use it on anything.

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Old 11-12-2014, 09:31 PM   #16
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Originally Posted by Wildflyer View Post
Just how does a clamp-on DC amp-meter work?
I was taught that it took a pulsating or alternating current in a wire which creates a varying magnetic field around the wire to induce a voltage in another wire.

This is how a common transformer works.

If it responds to pulsating DC current, does it give us the; average current, RMS current, or peak current ? What does the readout of a standard wattmeter display ?

I had a CC PH 25 ESC getting very hot very quickly, even though my Astro wattmeter showed only 2 amps ( this was a small formed can motor, <50 grams ) this would happen at low throttle, at high throttle, the speed control would cool off.
Castle engineers told me I had a "high wind" motor which created a condition that would require an oscilloscope to determine the actual amperage going through the ESC.

That problem told me, sometimes our instruments can play tricks on us.
I have not had any other motor do this. I did not use it on anything.
You're right, these AC only clamp on ammeters work by transformer action, very similar to a current transformer. Current transformers are widely used in the electric power industry, where they are used to measure currents from fractions of an Amp to 20,000 Amps or more. In fact, I've got an old current transformer from work that was rejected. It's maximum current rating is 24,000 Amps. It weighs some 15 pounds.

For DC currents, generally a shunt resistor is required for the higher currents. This is what is used inside those wattmeters. Now days, they have Hall Effect sensors that can respond very nicely to static magnetic fields, such as that present around a wire carrying DC currents.

The clamp on ammeter magnetic circuit still uses the laminated steel used in the AC clamp ons, but the sensor is now the Hall Effect or similar type of unit.

Before retiring, the company I worked for started using these hall effect types of current transformers in place of wound transformer current transformers. Those hall effect units were about the size of your thumb, and were extremely accurate over the range of a few milliamperes to 10 or 15 Amps. These were used in computerized circuit breaker controls which had to hold accuracy to plus minus 0.1%.

http://www.cy-sensors.com/HallCurrent.htm

As far as your ESC getting hot, that would result from very high peak currents flowing through your motor, and its very low inductance windings. It might even involve magnetically saturating the steel core of your motors rotor. If that happens, the winding pretty much turns into a dead short under AC conditions. As indicated, you'd only see that with an oscilloscope by putting a shunt in series with one of the motor wires, and connecting the scope across it. You'd need a clamp on ammeter that measures RMS AC current to measure the motor wire current. Problem is, that ESC puts 10 KiloHertz or so frequencies on the motor, which is way above the ability of most clamp on AC meters to measure,.

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