Because there is a semiconductor/chip inside the sensor, it must be powered with 3 - 5V to function. Contrast this to photocells and FSRs where they act like resistors and thus can be simply tested with a multimeter.
When the detector sees IR signal, it will pull the output low, turning on the LED - since the LED is red its much easier for us to see than IR!
Here we will connect the detector as such:
We will use 4xAA 1.3V batteries (I use NiMH) so that the voltage powering the sensor is about 4V.
2 batteries (3V) may be too little. 3 Batteries should be fine if you have a triple-AA holder
You can also get 5V from a microcontroller like an Arduino if you have one around. Ground goes to the middle pin.
The positive (longer) head of the Red LED connects to the +6V pin and the negative (shorter lead) connects through a 200 to 1000 ohm resistor to the first pin on the IR sensor.
Now grab any remote control like for a TV, DVD, computer, etc. and point it at the detector while pressing some buttons, you should see the LED blink a couple times whenever the remote is pressed.
If you have any questions on what is an ir light. We will give the professional answers to your questions.