Need to know more about how Chi works and how people sense it? Well just use those peepers of yours to find out. I know. I know. It's rough to read for ever, but that what this site is about. I'll stop wasteing your time and let you read.

What is Chi?
Chi is the life energy that all living things have. Most people have such minamle Chi that you can't sense them. Chi can be channeld to make you fly or create an energy attack. Chi can be focused like the Distructo Disk and it can be controled like Freeza's Energy Disks. The Energy Disks are moved by moving the hands.

How to sense Chi.
The people on Earth leared to sense Chi with no aid of machines. They feel the Chi in their body and can tell from what direction it is comming from. Other races are also capable of this as well. Other races who can't sense the Chi use things called scouters. The scouters are machines attach to the ear and have a piece of glass over the eye displaying all the information need. This information includes what the exact power level of the person they are reading is, the direction it is comming from if it is far away, and a transmitter.

People who can sense Chi.
People who can't sense Chi.