文档介绍：Fundamentals of Measurement Technology (8)
Prof. Wang Boxiong
Chapter 4 Acquisition of measurands
Introduction
Transduction implies the conversion of a measured or observed quantity, the measurand, into an electrical, hydraulic, pneumatic, or any other output by means of a transducer or sensing element.
The device employed to plish this conversion is known as a transducer or a sensing element (sensor).
Transducer and sensing element are two different concepts.
Sensing element : the element or unit which directly senses and converts the measured quantities
Transducer : the whole device consisting of a sensing element with its associated ponents and circuits, the sensor or sensing element being the ponent
Introduction
Since we are mainly interested in signal conversion laws of different devices and do not care for whether it is a sensing element or a transducer, so we do not distinguish between a transducer and a sensing element and generally refer to such a device as a transducer if no additional explanation is given. Since a transducer is located at the input of measuring instrument, its quality will influence directly the performance characteristic of the whole instrument.
Introduction
We hope to acquire measurands with no errors.
If the characteristic curve is a straight line, the transducer is known as a linear transducer.
But in most cases, the characteristic of a transducer is not a linear one, and the transducer is called a nonlinear transducer.
Introduction
Different ways are employed for the classification of transducers
One way is to classify transducers in terms of measured quantities:
Force transducers
Velocity transducers
Temperature transducers
Classifications of transducers
Another way is to make the classification in terms of the operating principles of transducers or the signal converting principles in transduction
Structure-type transducers : transduce signals by its structural variations
Capacitive transducer