Alt-BEAM Archive
Message #11959
To: BEAM beam@sgiblab.sgi.com; alt-beam@egroups.com
From: David Simmons devs@idirect.com
Date: Thu, 16 Mar 2000 07:35:36 -0500
Subject: Current draw of DC Motors
> Hey all,
>
> I was out today with my son looking to upgrade his Multi-Meter--His
> first was one I had to pick up on the quick several years ago when I was
> working on a site out of town and had to debug a new CNC machine being
> installed over the phone with a tech in Austria.
>
> All we really wanted was something that would show Current draw on a DC
> motor, that seems to be the only feature his current meter is lacking.
> The salesman was very willing to show us a range of meters from $20.00
> to well over $200.00 but once we got talking he told me a little way
> around the meter problem without any need to up grade the meter.
>
> He said to place a 10 ohm 10 watt power resistor between the plus
> termianl and the motor. Measure the voltage across the resistor and use
> Ohm's law to find the current.
>
> I = E/R
>
> Thus 1.21 volts across the resistor would be:
> I = 1.21 / 10
> I = .121 Amps or 121 mA
>
> Is this correct? Or am I way out to lunch here?
>
> Thank you,
> Dave
>
>
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