Photogate is the external sensor we use in Reaction Time and Speed measuring experiments. If your photogate is not showing any change or fluctuating, here are a list of steps you can use to diagnose the problem:
Sensor not showing any change:
If the photogate is not showing any change to the environment, the most probable reason is that the power cord is not connected. Since Photogate is among the sensors that require external power source to be connected, make sure that the cable is properly plugged-in.
A visual indicator of this is the small white led on the Photogate. It should turn on when you connect it to the MeasureLab console and turn off when you place an obstacle between the gate.
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Sensor displaying fluctuations:
If sensor displays rapid fluctuations when you place an obstacle inside the gate, that probably means that your Photogate is not properly calibrated.
It can be easily calibrated inside the software by these simple steps as follows:
- Download and open the Troubleshoot file.Troubleshoot .plf (76.2 KB)
- Once downloaded, open the file in the “Physlogger” software.
- In this file, there are two separate workspaces, Voltage A and B, each dedicated to it’s specific channel, either A or B. If you have connected your Photogate in channel A, go to Voltage A troubleshoot. Otherwise, go to Voltage B Troubleshoot.
- On this screen, pass different sample objects e.g. your fingers, toy car etc. through the Photogate. You will see pulses on both graphs:
- The upper and lower graph show the Photogate changes while the blue line in the center is the threshold value. This value determines how the photogate reacts to change. You can use the slider on the right to adjust this value.
- Once you have some sample signals, adjust the slider so that the threshold value is in the middle of your pulses:
- Once the line is in the middle, your photogate is calibrated. Note down the threshold value you have chosen:
Now, you can use this value in any of your experiment with a similar setup(same or similar objects passing through the Photogate). You can manually insert this value in the Photogate options in the Quantities Menu:
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If you are still facing issues with your Photogate or Calibration, feel free to comment under this post.