(Fwd) Re: Smart PASCO Pulley

["Robert Morrison" <morrison@pasco.com>]

Forwarded message:
From:     Self <Morrison.TechSupp.MktSls.PASCO>
To: phys-l@atlantis.cc.uwf.edu
Subject: Re: Smart PASCO Pulley
Reply-to: morrison@pasco.com
Date: Mon, 31 Mar 1997 12:21:06 -0800

    Dear Tim, Bob, Sam,John,and anyone that might be interested,
    Science Workshop has a default Digital Sampling Rate 10 KHz. The 
adjustable sampling rate is for Analog sensors, the Rotary Motion 
Sensor, and the Nuclear sensor. In a perfect world this would mean 
the Smart Pulley could be measured at rates up to 500 RPS. The 
reality is some signal aliasing does occur. At high revolution rates 
the smart pulley data stars to look like a step function. This is the 
reason for the erratic acceleration data. With the Smart 
Pulley, acceleration is calculated from velocity data, and the 
velocity is calculated from distance and time. Any small error in 
time or position, is magnified with each subsequent calculation. This 
Also contributes to strange looking acceleration data.
     Science Workshop shows data in its rawest possible form, but 
includes the ability to smooth data. In the Experiment Calculator 
Special Functions submenu, You will find a Smooth function. When you 
first select the Smooth function the "x" parameter should be 
highlighted. If you make a selection from the Input menu at this 
point, it will replace the "x". The "n" is the number of points you 
wish to smooth over. The Users Guide has more detail on using the 
experiment calculator. If you are running an older version of 
Science Workshop, you can update to the latest version at our web 
site:
http://www.pasco.com
Hit the red Demo button on the homepage graphic to get to the 
software download page.
Yours,
Robert  

> I was using the Smart PASCO Pulley today with Science Workshop Software.
> The smart pulley is in constant contact with a rotating disk so that
> as the disk spins the smart pulley spins.
>
> The angular acceleration should be negative at all times during a
> "spin down" of the disk (the angular velocity constantly decreases on
> the table and graph of data).  Instead there is an alternating pattern
> of negative and positive angular accelerations on both the table and
> the graph of the acceleration.
>
> Is anyone familar with this equipment and results? 
>
> Writing this note makes me wonder if there is a data sampling rate that 
> needs tweaking...but the question is posed for assistance! Thanks.
>
> Tim Burgess
>
>  
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