define(`TITLE', `Measuring the speed of a salad spinner')
define(`DATE', `2014-12-11')
define(`CONTENT', `
Have you ever been wondering with how many revolutions your salad spinner is running? Here is the measuring:

First, attach a hall-probe to the salad spinner bowl, the exact position needs to be found by experiment:

<a href="http://a385e-5.de/wp-content/uploads/IMG_2597.jpg"><img src="http://a385e-5.de/wp-content/uploads/IMG_2597-300x225.jpg" alt="IMG_2597" width="300" height="225" class="alignnone size-medium wp-image-507" /></a>

Second, attach two small but strong magnets at the spinner, one on each side, to let it run weighty:

<a href="http://a385e5.files.wordpress.com/2014/12/img_2600.jpg"><img src="http://a385e-5.de/wp-content/uploads/IMG_2600-300x225.jpg" alt="IMG_2600" width="300" height="225" class="alignnone size-medium wp-image-508" /></a>

Third, connect the probe to a power-supply, an oscilloscope and a frequency-counter:

<a href="http://a385e-5.de/wp-content/uploads/IMG_2599.jpg"><img src="http://a385e-5.de/wp-content/uploads/IMG_2599-300x225.jpg" alt="IMG_2599" width="300" height="225" class="alignnone size-medium wp-image-509" /></a>

The oscilloscope is required to find the right position of the probe, the counter is required for the actually measurement.

And then: turn the spinner:

[youtube https://www.youtube.com/watch?v=ezTvoh3vguI&w=560&h=315]

Here, in this clip, we measured about 43Hz. In another test it was even 52Hz.

Since we have two magnets, we had 21.5 rps and in the other test 26 rps. These are 1290 rpm and 1560 rpm. That'`s fast.
')