What lie detector record?

Research : 

How does a lie detector (polygraph) work?

Source: How Lie Detectors Work
http://science.howstuffworks.com/question123.htm

My Topic: The lie detector is not always accurate.

What I hope to learn from this source:

I want to know the principles of the lie detector more simply. 

Notes.

1. The lie detector usually record this things.

• The person's breathing rate
• The person's pulse
• The person's blood pressure
• The person's perspiration

And the lie detector determines lie or not based in this results. 

2. When a well-trained examiner uses a polygraph, he or she can detect lying with high accuracy. However, because the examiner's interpretation is subjective and because different people react differently to lying, a polygraph test is not perfect and can be fooled.

>>>>Final Thoughts:
1. I want to know how the lie detector works.
And I can learn the lie detector's principals from this research.
According to the research, It usually record the person's breathing rate, pulse, blood pressure, and perspiration. And based on this records, it distinct the lie.

2. And accidently, I found some possibility that the lie detector can not be accurate.