In this tutorial, we are going to learn about Best Tutorial on Transducer
Transducer-
An instrumentation system is meant to measure a physical quantity after it is converted to an electrical quantity and processed for measurement, manipulation and / or control. The non – electrical physical quantity in a real word is converted into an electrical signal by means of a transducer. A transducer is thus a device that converts and transforms one form of energy into another an efficient transducer transforms maximum information and minimum energy. A widely accepted and used definition of a transducer is that it is a device which provides useful output in accordance with a physical quantity, property or condition under measurement.
Transducer has two major functions –
- To measure/to sense and
- To convert the measured/sensed value to a useful output. Depending on the type of output from the transducer those results, there may or may not be a conversion function.
Selection of a transducer-
Measurement – While selecting a transducer for any specific quantity being measured, the following
Criteria should be considered:
- Type of quantity being measured
- Number of measurements
- Sensing element
- Transduction element
- Range of measurement.
Conversion- The conversion involves presentation of measured value in a specific format to the user.
For example, in some cases the measured value needs amplification. Some transducers involve the conversion of AC output from the transducer element to DC output .Some transducers even convert analog signal to digital so that they can be interfaced to computer directly. Depending on the application, the quantity being measured is converted in a processing module of the instrumentation system.
Advantages of Electrical Transducers-
Electrical transducers give an electrical output in accordance with the quantity being measured.
The advantages of converting physical quantities into analogous electrical quantities below-
- Electrical attenuation and amplification can be done easily and that too with static devices.
- The mass-inertia effects are minimized. In fact, when dealing with electrical or electronic signals, the inertia effects are due to electrons that have negligible mass. In many situations. We do not come across a mass or inertia problems at all.
- The effects of friction are minimized.
- The electrical systems can be controlled with a very small power level.
- The output can be easily used transmitted and processed for the purpose of measurement.
- Telemetry and remote control are made possible. The entire aerospace research and development has been made possible due to telemetry and remote control. The remote indication or recording is an essential part of modern day instrumentation technology.
- There has been a tremendous development in the field of electronic components, devices and miniaturization on account of use of ICs.
Classification of Transducers-
Classification on the basis of transduction form used
- As primary and secondary transducers
- As passive and active transducers
- As analog and digital transducers
- As transducers and inverse transducers
Primary and secondary transducers-
In some cases, there are two stage of transduction. For example, when measuring pressure by use of a Bourdon tube, and an LVDT, the Bourdon tube acting as a primary detector senses the pressure and converts it into a displacement of its free end. The displacement of the free end is converted into an analogous voltage signal by means of an LVDT.The Bourdon tube is called a primary transducer and the LVDT is called a secondary transducer.
Passive and active transducers-
Passive transducers derive the power required for transduction from an auxiliary power source. They also derive part of the power required for conversion from the physical quantity under measurement and it is also known as externally powered transducers. Typical examples of passive transducers are resistive inductive and capacitive transducers. Active transducers are those, which do not require an auxiliary power source to production of output signal is obtained from the physical quantity being measured. Velocity, temperature, light intensity and force can be transducers include techno – generators, thermo couples, photovoltaic cells and piezo – electric crystals.
Analog and digital transducers –
Analog transducer – It convert the input quantity into an analog input, which is a continuous function of time. While a strain gauge, an LVDT, a thermocouple or a thermostat may be called as analog transducers as they give an output, which is a continuous function of time.
Digital Transducer – It convert the input quantity into an electrical output, which is in the form of pulses. The binary system uses only two symbols 0 and 1, these symbols can be easily represented by opaque and transparent areas on a glass scale or non -conducting and conducting areas on a metal scale.
Transducers and Inverse transducers-
In practice, measurement and control of physical and electrical quantities is involved. In closed loop control systems, often feedback is employed. A transducer can be broadly defined as a device, which converts a non electrical quantity into an electrical quantity. An inverse transducer is defined as device, which converts an electrical quantity into a non electrical quantity. It is a precision actuator, which has an electrical input and low power non-electrical output. A block diagram of a feedback control system using inverse transducers is shown in figure below-
Transducers and Inverse Transducers-
Examples of inverse transducers are – piezo electric crystal where a voltage applied across its surfaces causes a change in the dimensions across its surfaces cause a change in the dimensions of the crystal causing a mechanical displacement; a current carrying coil moving in a magnetic field wherein the current carried is converted into a force which cause translational or rotational movement, many data indicating and recording devices.
Classification based on principle of transduction-
The transducers can be classified on the basis of principle of transduction as resistive, inductive, capacitive, etc., depending upon how they convert the input quantity into resistance, inductance or capacitance respectively. They can be classified as piezoelectric, thermoelectric, magneto restrictive, electro kinetic and optical according to the principle involved.