Vernier BTA and BTD sensors all work based on 5-volts.  For more information on that go to https://www.vernier.com/engineering/arduino/

Most Arduino models work based on 5-volts.  A few, mostly newer, Arduino models are based on 3.3 volts. We do not recommend using the 3.3-volt Arduinos with our sensors for the following reasons:
– You might damage the 3.3-volt Arduino using our sensor. There is a slight risk the sensor could provide an output of greater than 3.3 volts. Here is the warning message on the Arduino Due web site: Warning: Unlike most Arduino boards, the Arduino Due board runs at 3.3V. The maximum voltage that the I/O pins can tolerate is 3.3V. Applying voltages higher than 3.3V to any I/O pin could damage the board.
– The Arduino’s A-to-D converter cannot read the sensor output properly. On most (5-volt) Arduinos, the A-to-D converter reads a count of 0 to 1023 representing voltages from 0 to 5 volts. On the 3.3 volt based Arduinos, the A-to-D converter reads a count of 0 to 1023 representing voltages from 0 to 3.3 volts.

Here is a list of Arduino Models that are based on 5-volts, which we have used successfully:
Arduino RedBoard (the one we sell)
Arduino Uno (similar form to Redboard)
Arduino Mega 5V
Arduino Leonardo
Arduino Micro (5-volt version)

Here is a list of other 5-volt Arduinos, which should work fine, but we have not tested:
Arduino Pro 5V/16MHz
Arduino Mini 05
Arduino Pro Mini 5V/16MHz
Arduino Ethernet
Arduino Pro Micro 5V/16MHz
Arduino Mega Pro 5V
Arduino Yun

Here is a list of 3.3-volt Arduinos, which you should not use with our sensors:
Arduino 101
Arduino Genuino
Arduino Due
Arduino Gemma
Arduino Zero
Arduino Pro 3.3V/8MHz
Arduino Fio
Arduino LilyPad
Arduino Pro Micro 3.3V/8MHz
Arduino Mega Pro 3.3V
Arduino Mega Pro Mini 3.3V

Arduino and SparkFun RedBoard Troubleshooting and FAQs

Note that our Go Direct(GDX) Bluetooth sensors, can also be used with some Arduinos. We have a separate Arduino library for that. See Can I use your Go Direct(GDX) sensors with an Arduino?