This information applies to a Vernier (BTD) Photogate
For information about measuring acceleration using Go Direct Photogates, see
How do you measure acceleration using Go Direct Photogates (GDX-VPG)?
First, you need to understand some terminology we use with photogates:
“Gate timing” means timing how long a photogate is blocked.
“Pulse timing” means timing how long between the times when photogates are blocked.
Now, the key to using photogates with Logger Pro 3 is usually to open a file from the folder:
Experiment Files / Probes & Sensors / Photogates
Choose the one that matches what you want to do. If you are not using Logger Pro, see the guide that matches your software at: Vernier Photogate (VPG-BTD) Troubleshooting and FAQs
To measure acceleration, there are several options:
– Use a picket fence and one photogate:
For the most data, you need to use a picket fence object mounted on the moving object. You only need one photogate and you get D, V, and A. vs time. This is what we call “Motion Timing”.
– Use a “flag” on the cart and two photogates
If you do not want to use a picket fence, you can use two photogates. To do this, open the file Gate and Pulse Timer. This file is to be used with a cart with a “flag” of known length. It does three timings automatically. It does a “gate” timing of how long it takes the cart to go through each of the two photogates. That allows calculation of two speeds. It also times the time from the mid points of the two gate times. This gives Logger Pro the info needed to calculate the average acceleration. In the Gate and Pulse Timer file, you set the length of the flag on the cart as Photogate Distance 1. Note that the distance between the photogates is not involved in the calculation.
– Use three or four photogates
If you use three or four photogates which are daisy chained together, you can just use the file Pulse Timer – One gate. This will give you multiple velocities and you can calculate the accelerations from the change in velocity. Remember that for the delta time figure, you should work with the mid-point times of the different pulse timings.
Please try this file.