How to measure fan draw

Danfoss2011 · 17 May 2011 at 21:51

How do i go about measuring the power draw of my fans?

AMPS would be the best as i can work out WATTS from that.

Voltage be handy as well i guess

Marvin · 17 May 2011 at 21:52

Multimeter?

Danfoss2011 · 17 May 2011 at 21:58

Marvin said:
Multimeter?

Gathered that but where about should i measure?

Surveyor · 17 May 2011 at 21:59

Doesn't it say on them?

The fans will be 12V (unless using some sort of reducer) and usually have the amperage printed on them.

From that you can work out the wattage.

I'm looking at a Cooler Master 200mm fan now which says it's 0.28A.

12V x 0.28A = 3.36W

A Cooler Master 140mm fan is 0.14A.

12V x 0.14A = 1.68W

Frozennova · 17 May 2011 at 22:04

Look on the manufaturers website, it shuld give you all the details needed.

Example: http://www.scythe-usa.com/product/acc/051/d1225c12b1ap_detail.html

Danfoss2011 · 17 May 2011 at 22:12

Surveyor said:
Doesn't it say on them?

The fans will be 12V (unless using some sort of reducer) and usually have the amperage printed on them.

From that you can work out the wattage.

I'm looking at a Cooler Master 200mm fan now which says it's 0.28A.

12V x 0.28A = 3.36W

A Cooler Master 140mm fan is 0.14A.

12V x 0.14A = 1.68W

I don't fully trust Yate loon

Fans are 12v and they say 0.70A but i want to check

12V X 0.70A = 8.4W

Surveyor · 17 May 2011 at 22:16

Which Yate Loon fan are you looking at?

Danfoss2011 · 17 May 2011 at 22:31

Yate Loon D14SH-12 got 8 of them. Trying to workout power for a reohstate

Surveyor · 17 May 2011 at 22:37

According to Yate Loon those are 2800RPM fans:

http://www.yateloon.com/detail/38839/38839.html

I would imagine the power draw would be quite high.

Danfoss2011 · 17 May 2011 at 23:00

Yeah they move some air and are loud so i want to control them but just via one control

Danfoss2011 · 18 May 2011 at 07:42

Anyone want to check over this and see if im making an sense

For the sake of the argument, let's say I want to go from 12v to 6v. In that case, I want to match the "resistance" of the fan, which is 12v / 0.70A = 17.14ohms. Assuming a linear relationship between fan voltage and current. the fan will draw 0.35A at 6v.

There are 8 fan all to run off one control

Therefore, the rheostat will need to dissipate 2.8A * 6v = 6.8W. But I guess i should allow for some head room but how much?

MikeHunt79 · 18 May 2011 at 08:12

A multimeter is what you need to use, you need to connect it in series to measure current.

Danfoss2011 · 18 May 2011 at 09:04

MikeHunt79 said:
A multimeter is what you need to use, you need to connect it in series to measure current.

Thank you!

Once they have powered up 2.50/51A, up on powering up 3.50A is the max I've seen this is @ 12V

Now to work out a rheostat specs

Danfoss2011 · 18 May 2011 at 11:52

Noticed my multimeter was off on my bench PSU. Upon looking i noticed the probe wires had split. I needed to get a new one so i solder the same wires i'm using on the fans directly to the PCB.

Sorry for the lame photos, there video off phone then via pause and print screen. I played them slow so i could see the peak.

SATRT UP FANS ONLY

5 MINS RUNNING FANS ONLY