PIRA 1C30.10 Measuring g: - Freefall Timer -

The image shows the demonstration used at the University of Texas at Austin.

• The demo uses an electronic timer, a steel ball, an electromagnet at the top of a ring stand and a mechanical cut-off switch.


• The distance between the electromagnet at the top of a ring stand and the mechanical cut-off switch is one meter.


• Do not attempt to adjust the distance between the electromagnet and the mechanical cut-off switch.


• The mechanical cut-off switch interrupts a circuit with in the clock - which stops its measurement.


• Do note that the mechanical cut-off switch needs to be reset between runs - It is labelled as an interruptor switch on the bottom most image on this web page.
  

Image below shows a closer view of the Leybold timer used for this demo.

Instructions / Notes - continued :

• Be familiar with two of the small, black buttons on the front panel of the Leybold timer.


• The black button on the right is used to reset the timer to zero seconds after each data run.


• The black "Start/Stop" button on the left releases the ball from the electromagnet at the top of the ring stand.


• The reset procedure for a second data run requires 2 steps.


• Push the reset button on the front panel of the timer.


• In the catch basket at the bottom of the ring stand - push down on inner most end of the interruptor switch - where the number 2 is written.


• (See the bottom most image for more details.)


• Demo Staff: This demo needs to be set up and tested on the day before it is needed.


• The interruptor switch - (which acts as the timer's remote cut-off switch) - is located at the bottom of the ring stand.


• It is a mechanical switch that can get sticky after several uses, at which point the clock will run continuously after the ball drops.

The final image shows the timer's cut-off switch, located in the bottom of the catch basket. - It needs to be reset between data runs.