Response Time Box
What is it for?
The Response Time Box is designed to measure response time with high accuracy. The microprocessor in the device records the time and button identity. The user code can read the information anytime when it is convenient.
Why do I need it?
Computer keyboard and mouse can be used to record response time to an event, such as visual or auditory stimulus. But one can get only the time when user code reads an event, such as key press, not the time the event happens. Many things can affect the time difference between key press and event read, such as hardware sampling interval, debouncing interval, operating system, programming software, and user code etc. The variability makes the regular keyboard and mouse unusable for high-accuracy response time experiments. Our device avoids all of above problems, and will give you accurate time of an event.
Features and Specification
- Work on major computer systems (Windows, MAC and Linux)
- USB 1.1 and 2.0 compatible
- Measure both the button press and release time
- Built-in light port and sound port for trigger and calibration
- Four buttons allowing user to label with descriptive names
- Receive input from external buttons and TTL such as MRI-compatible keypads
- TTL output to control other devices or for EEG event code
- TTL output for all button and trigger events, useful for EEG recording
- Built-in firmware update feature, so the device will never expire
- Time resolution: about 6 µs with latest firmware (~90 µs before)
- Dimensions: 5.5 x 4.5 x 1 (h) inches, 14 x 11 x 2.5 (h) cm
- Weight: ~5 oz
- Some features are customizable. Feel free to ask.
What is in the package?
- Response box
- USB cable
- Photodiode with rubber suction and cable
How does it work?
When the device is connected to a USB port of a computer, it will be recognized as a serial port. The device is USB powered.
Basically, the device detects button and port events with an interval less than 0.1 ms. When it detects an event, it sends the event code and time to the computer serial port. At the computer side, the device driver reads the data from serial buffer, identifies the event type, and calculates the response time.
The critical thing is to give the device a signal indicating onset of a stimulus. The device can receive three kinds of trigger for this purpose. The sound port receives an electrical pulse or sound signal, the light port receives light signal from the provided photodiode, and the device can also receive a trigger from the computer serial port without additional hardware connection.
The trigger from serial port can also be used to synchronize the device clock with computer clock. Then the device driver can return computer time directly. If you have computer-based stimulus onset time, such as those from Screen(‘Flip’) of PsychToolbox 3, you don't need any external trigger.
How to use it?
There are two ways to use the device to measure response time. If the stimulus onset time based on computer clock is available, the driver code can convert device time into computer time. Then a simple subtraction will get the response time.
The second way is to provide a trigger to the device to indicate the onset of stimulus. The device will detect both trigger and button events. The time difference between the two events will be the response time.
We provide driver code and demos based on PsychToolbox in MatLab/Octave (updated 05/09/2017) and driver code and demos in Python (updated 05/09/2017). For detail principles, you can check our paper on Behavior Research Methods.
How to calibrate it?
The light and pulse ports provide convenient way for calibration. Normally, there is no need to calibrate the response box itself. However, these ports can be used to calibrate the time difference between the trigger signal (real stimulus onset timestamp) and the nominal onset time from software.
Only the latest hardware version is available for order. The price is $300 each for the response box, plus shipping and handling, which is $45 for the first one, and $10 each for additional ones. The payment can be made by a check, wire transfer or credit/debit card via Paypal.
If you want to make an order, have question or suggestion about the device, please contact us by email firstname.lastname@example.org .
Last updated on 05/09/2017