----- Original Message -----
From: "Robinson, Chad" <crobinson@rfgonline.com>
Date: Wednesday, October 15, 2003 11:00 am
Subject: [FlyRotary] Re: EWP - series pumps and wacky ideas

> Yeah, that would be fairly simple. Tell me, where do you want this
> to be triggered? I'm a bit confused about what you're trying to
> sense. Do you want to know when the pump is full on? Full off?
> Partially on?
>
> To be honest, current sensing isn't all it's cracked up to be. One
> of the most useful things to detect would actually be when you
> have the pump turned on but it isn't working. The thing is, that
> means you have to sense when voltage is applied but no current is
> flowing. That's easy enough. But most motors don't fail open, they
> short out, so current WOULD flow, and your breaker or fuse would
> blow, and there's your indication.
>
> So the fuse might be the BEST option.
>

Just an unsubstantiated brain fart, but it seems to me that all those are really secondary measurments.  The really important point whether the impeller is spinning properly.  Would it be possible to install a tiny magnet in the impeller and detect it's passing with a sensor?  Could the same data be used to determine the pump's speed, indicating pump health and flow rate?