Precision LM4040 Voltage Reference Breakout - 2.048V and 4.096V is a voltage reference module which can be used as a reference to your analog to digital converter or to test your microcontroller’s conversion accuracy and precision. The board has two very high precision shunt-type voltage references with 750 ohm biasing resistors. One is 2.048V (great for 3.3V reference systems) and the other is 4.096 (great for 5V). Both are 0.1% accuracy.
Using the board is easy, just power with about 5V-12V, or 3V if you want only the 2V reference to work. Then measure the voltage on the output. Note that Precision LM4040 Voltage Reference Breakout - 2.048V and 4.096V is not a regulator, you cannot power anything off the output. They are for measurements only.
Adafruit Web Site: https://www.adafruit.com/product/2200