Types of Transducers and What they Do

What is a transducer? 

Transducers are devices that convert energy from one form to another. Transducers are all around us. An example most of us are familiar with includes microphones and loudspeakers.

When we think about transducers, there are two basic types to think about. An input transducer is a sensor, and an output transducer is an actuator.

An input transducer, or sensor, responds to a change in the environment and converts it into an electrical signal which can be read. In our microphone example, the microphone takes physical sound waves and turns those into an electrical signal which is transferred through wires to the amplifier.

Output transducers, or actuators, do the opposite of an input transducer. They take electrical signals and convert them into another form of energy.

For example, a lamp converts electricity to light and a motor converts electricity into motion.

Transducer sensitivity is defined as the ratio of an output quantity to an input quantity. Sensitivity is a key indicator of a transducer’s performance.

Transducer efficiency is described as the ratio of the power output in the preferred type to the total power input. Basically, no transducer is completely efficient, as a certain amount of power is often lost during the conversion process. Some transducers are usually more efficient than others.

In this article, we’re going to take a deep dive look into the world of transducers, with particular emphasis on sensors. We’ll explore the different types of transducers and their applications. We’ll get a better understanding of how transducers work and a lot more.

What is a Transducer Used For?

A transducer converts energy from one sort to another. Generally, transducers convert one type of energy, for example, mechanical or magnetic, into something you can measure on the other end, an electrical signal. You can also go the other way as well and convert an electrical signal into something else, like a mechanical movement.

How Many Types of Transducers are There?

Lots! Almost too many to mention. We’ve mentioned some above – current transducers, magnetic field transducers, voltage transducers. Microphones, speakers, thermocouples. Antenna transmitters and receivers are also transducers.

Current transducers

Current transducers are used when going from a primary current source to a secondary signal output that we can measure.

Magnetic field transducers

Magnetic Field Transducers are used when going from a magnetic field source to a signal out that we can measure.

Pressure transducers

Pressure Transducers or force transducers and convert physical force into a number or reading that can be measured and understood. These are also referred to as a load cell.

A piezoelectric transducer

A Piezoelectric Transducer converts the electrical charges produced by some forms of solid materials into energy. Piezoelectric transducers use the word “piezoelectric” as it literally means electricity caused by pressure.

Thermocouples

Thermocouples which are like electronic thermometers measure voltage changes and prevent our phones, thermostats, and cars from overheating.

An Electromechanical transducer

An electromechanical Transducer is any type of device that either converts electrical signals into sound waves (as in a loudspeaker) or converts a sound wave into an electrical signal (as in the microphone).

Mutual induction transducers

Mutual Induction Transducers rely on two coils for mutual induction. One for generating excitation and another for output.

Strain gauges

Strain Gauges are types of transducers that convert a physical quantity such as a load, pressure, or displacement into mechanical strain on the strain generating body. The strain is converted into electrical output using mounted strain gauges.

What is the Difference Between a Sensor and Transducer?

A transducer is broader and includes both sensors and actuators. A sensor specifically reacts to something in the environment – mechanical, electrical, temperature, pressure, and so on, and converts it to an electronic signal to be recorded or analyzed elsewhere. So generally, a sensor is a type of transducer.

What are the Main Parts of a Transducer?

When talking about sensor transducers, you have the sensor head, the part that reacts to change in the environment. The environmental change could be magnetic field (and remember, electric current moving through a conductor generates the surrounding magnetic field), temperature, pressure, and so on. You then need to convert that into a usable electric signal, so there is some sort of electronics involved.

That could be something as simple as a resistor converting induced voltage to current and vice versa. It could also be an amplifier to strengthen a very small signal to something useful. Or even an integrator circuit to translate the rate of change in current into the actual underlying current waveform.

Products and reference designs of transducer

Non-isolated AC/DC power supply

In a transducer the auxiliary supply output is typically drawn from mains AC. It is stepped down to 5V or 12V using the LDO, Flyback and DC/DC converters. Use of DC-DC converter improves efficiency of the power supply. Non-isolated AC/DC power supply includes Flyback controllers、Linear & low-dropout (LDO) regulators、Buck converters (integrated switch), the corresponding products are LM5021、TPS7A03、TPS568231

Isolated AC/DC power supply

The AC/DC power supply for operation can be self-powered or auxiliary powered. Depending on the functionality an isolated AC/DC or non-isolated AC/DC power supply configuration can be chosen. The choice of isolated or non-isolated AC/DC power supply depends on the power requirement, form factor and efficiency requirements. Isolated AC/DC power supply includes Flyback controllers、Linear & low-dropout (LDO) regulators、Series voltage references, the corresponding products are UCC28711、TPS7A05、REF70

Isolated DC/DC power supply

Isolated DC/DC power supply is used to generate power supply for the communication module. We have devices that can realize small and efficient fly-buck, fly-back and push pull topologies. Isolated DC/DC power supply includes Transformer drivers、Linear & low-dropout (LDO) regulators、Isolated DC/DC converters & modules, the corresponding products are SN6501、TPS7A20、UCC12050

Signal input protection

In a transducer, the analog inputs have to be protected against EFT, surge and ESD. The protection device can be selected based on the application and standards requirement. Signal input protection includes TVS diodes、ESD protection diodes, the corresponding products are TVS1400、TPD1E01B04

Analog front end

In a transducer, analog front end includes signal conditioning amplifier to scale the sensor output to the ADC input range. Based on the input range a stable reference is used to level shift the bipolar sensor signal to unipolar ADC input signal. Comparators with hysteresis are used as zero cross detectors for measurement of frequency.  Analog front end includes Precision op amps (Vos<1mV)、Analog current-sense amplifiers、General-purpose op amps、Comparators、Programmable & variable gain amplifiers (PGAs & VGAs)、Precision ADCs、Series voltage references, the corresponding products are OPA2376、INA2180、TLV9004、LM2903、PGA117、ADS131E08、REF2025

Digital processing

In transducer a 16-bit or 32-bit MCU is used for measuring the analog inputs, processing the protection algorithm, user interface and external communication. Digital processing includes MSP430 microcontrollers, the corresponding products are MSP430F6779A、MSP430G2553

Output signal isolation

The data converter and the voltage/current driver need to be isolated from the MCU. The number of channels required is decided by the communication with the data converter, and the controlling and monitoring of the driver. Output signal isolation includes Digital isolators, the corresponding products are ISO7741、ISO7731

Wireless interface

Wireless interfaces in the form of Wi-Fi or Bluetooth are used for configuring the transducer or viewing the measured parameters locally using a hand held device or remotely for automation. Wireless interface includes Wi-Fi products、Low-power 2.4-GHz products、Sub-1 GHz wireless MCUs, the corresponding products are CC3220MODA、CC2651R3、CC1312R

Signal output protection

In a transducer, signal output protection is provided for the external RS-232/RS-485 interface output. The outputs are connected to networking system with long cables and operate in harsh conditions with high level of interferences. Signal output protection includes TVS diodes、ESD protection diodes, the corresponding products are TVS0500、TPD4E02B04

Output user interface

LED drivers are used for intensity control based on ambeint light and uniform 360 degree visibility. LED drivers with integrated temperature compensation can be configured and controlled by the MCU over an I2C interface. Output user interface includes Low-side switches、LCD & OLED display power & drivers、Light sensors, the corresponding products are TPL7407L、TPS65131、OPT101

Isolated DC output

Analog output circuitry is realized using a DAC and integrated analog voltage and current drivers allowing digital selection between voltage and current modes on a combined output pin. Isolated DC output includes Precision DACs (≤10 MSPS)、4-20mA signal conditioners, the corresponding products are XTR300、DAC8771

What is Signal Conditioning in a Transducer?

Signal conditioning is the technique of making a signal from a sensor or transducer suitable for processing by data acquisition equipment. For example, if you’re measuring a voltage signal smaller than a few millivolts, you might need to amplify it. If you had a signal contaminated with noise you could filter it.

Hope the article can help you a lot!