How to see infrared light

I cannot see infrared light through my bare eyes. Amazingly, I can see infrared light through the monitor of my phone camera.

This is an excellent way to check whether my infrared remote controller is sending out signals or not. In addition, I could also know whether the battery inside the remote controller is working or not.

The phone I am using to shoot this video is Samsung Galaxy S5.  This should be working on most of the digital cameras.

(Thank you for teaching me this tip, Martin!)