Re: Motion Sensor Light for Front Entrance

[nobody@xxxxxxxxxxxx (Dave Houston)]

>The Kill-A-Watt is notorious for not measuring very low wattage devices
>accurately.  My electronic wizard friend theorized that it's because they've
>optimized their reading range for items people would most likely measure.

Yes and no. It doesn't indicate fractional watts so you need to use the kWh
mode and measure over a long time frame. I measured several X10 modules this
way for ~100 hour periods. See...

     http://davehouston.org/x10-power.htm

NOTE: The readings were under no load conditions but I doubt that the
trickle current will be that significant.

>I've been fooled by it on a number of occasions.  An in-line amperage
>measurement is likely to show you something different.  Also, the X-10 power
>supplies have a rather unusual design which contributes, I think, to the
>Kill-A-Watt's erroneous readings.

In-line amperage measurements are worse than useless with non-linear loads
like these. The Kill-A-Watt takes thousands of instantaneous readings of
both voltage and curreny each second and then averages them to get a very
accurate reading. The kWh mode has 30ppm accuracy.

>IIRC, a while back Dave Houston (has anyone heard from him?) did some
>measurements that more accurately pegged them at five watts.

I've neen dealing with major health issues (and have additional surgery
scheduled). As for my measurements, I did exactly the opposite, refuting
numerous people who were claiming X10 modules used 5-10W based on ammeter
readings.

>If you have an in-line ammeter (the tong meters aren't really suitable,
>either, you might want to revisit the study with loads plugged into a batch
>of modules.

Don't waste your time - this method is, as noted above, worse than useless -
worse because it is extremely misleading.