Applications Process Control Introduction (LC)

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Applications: process control

There are numerous applications for the industrial market due to the many related sectors. EBV presents the most exciting application examples within the fields of:


Counters and timers

Industrial counter/timer combinations can perform both counting and timing functions and can be either single function or multi function, or programmable for more than one function

Industrial Counters are instruments for detecting, totalising and indicating a sequence of events. They may be mechanical, electromechanical or electronic devices, which can keep track of the number of input signals or pulses. Industrial Timers are used for automatically starting, or stopping, a machine or other devices. Elapsed Timers are used to measure the amount of time that an event took place. Electromechanical Timers acquire the time from the AC line frequency for AC inputs and use an asynchronous motor for DC inputs. Most Electronic Timers use a crystal oscillator to obtain the time. Applications include recording the operating time of machinery for maintenance, testing, leasing and warranty programs. Totalising Counters are used to count objects or events. They can be simple counters which count each time a voltage pulse is applied to the input or they can incorporate a scale factor which will allow the display to be in engineering units. Applications include Vending/Gaming Machines, Parts Counting, Flow Totalising and OEM Machinery.

Pump/valve controllers

A significant factor in the design of a pumping system is the flow variation required by the process

Several pumps in parallel, variable speed pumps, pumps with on-off control and pumps with a control valve are some of the methods available for flow variation. A widely used method in industry is to use control valves which are generally located on the pump discharge in the pipe supplying process fluid. The flow could be used for different purposes, such as maintaining the level in a process vessel or in a boiler drum, or maintaining the flow in a pipeline or in the tubes of a fired heater.The flow rate through a control valve depends on the size of the valve, the pressure drop over the valve, the stem position and the flow properties.

Temperature controllers

A temperature controller is a measurement device used in temperature control

Thermocouple-type and resistor-type temperature controllers measure temperature electronically by obtaining the temperature change from the sensor and sending the measured data to the electronic processor. The output device will then control the temperature variation within a specific range. An advanced temperature controller has fast output response, accurate PID parameter auto-tuning, supports different Industrial communication protocols (such as Modbus) and has various output types built-in. This allows stable control of different systems.

Interface converters

Interface converters are used to electrically isolate and convert analog signals

Sensors/actuators and controls often have different power supply units, and therefore require electrical isolation in the signal circuit. The conversion of analog signals allows transmission over longer distances and service interworking between different communication interfaces,. such as transparent adaptation of optical and electrical signals into various protocols. Interface converters enable media conversion from coax to twisted pair, UTP to Fiber, as well as single mode to multimode fiber conversion. They also allow service interworking between Ethernet to E1/T1 or E3/T3 and between E1/T1 to Ethernet.

Input/output modules

Process control techniques give rise to the need for input and output option modules that can be used to supplement the drive´s standard I/O for applications where the drive is used as the automation controller

The inputs are isolated from the logic by bi-directional opto-couplers. The outputs may be used to drive lamps or external relays when more drive capability is required. The outputs are isolated from the logic and they share a common negative terminal. Discrete Input and discrete Output modules usually contain 8-, 16- or 32- input or output circuits and can accept AC or DC voltage, depending on the model. Both the input and output circuits are grouped into four commons for each module. Isolation is provided between each of the four commons. The discrete input modules are particularly valuable in areas where applications such as limit switches or pushbuttons are needed. The discrete AC output modules are equipped with heavy-duty triacs, without zero cross circuits, to give a faster turn-on response.

Programmable relays

Programmable relays combine timers, relays, counters, special functions, inputs and outputs into one compact device that is easily programmed

They provide an exceptional level of flexibility together with substantial savings in commissioning time and effort. Relay Output Modules may contain 8-, 16- or 32-output points. These modules are particularly valuable for applications where:

  • “no leakage” output is mandatory in the off-state condition.
  •  load currents must be isolated.
  •  a mixture of voltages must be connected to the same module (for example, 24 VDC and 24 VAC).

When relay modules are equipped with isolated commons they can switch either AC or DC power at each common. These modules are less susceptible to inductive load transients than other DC-type modules when the outputs are turned on or off. Some modules provide snubbers on the normally open contacts. This snubber should be used with inductive loads to extend the contact life. If the load requires a “dry contact” relay then the snubber can be disconnected.

Fan/blower controllers

The term fan and blower are often used interchangeably and to many people the terms are synonymous. Rather like an engine or motor when referring to an internal combustion engine

A fan is just the air-moving device. It is attached to a shaft that is turned by a motor (usually electrical, but could be a gasoline engine). There are axial-bladed fans such as the ceiling fan in homes or in a window fan. Axial fans usually move large volumes of air at low pressure. Then there are centrifugal fans, of which there are 3 major classes: forwardly curved, backwardly curved or straight-bladed. They generally move less air but at a higher pressure. Some fans are called compressors if they turn at sufficient speed to materially compress the air they are moving. Centrifugal fans are usually mounted in a housing that looks like a snail shell. The inlet is in the centre and the discharge is the opening of the shell at the outer edge of the scroll. When the fan is integrated with a housing and a motor, it then becomes a blower which are usually small centrifugal fans. Because blower housings contain and direct the air to where it is needed, they are used in more applications than an open fan blade. Each fan type has its own characteristics, which dictate the choice for a particular application. Generally blowers are more effective at higher pressures than fans at lower pressures, which is why blowers are typically used in duct distribution methods. Fans are also quite sensitive to the amount of free air around them as the outside edge does the most work. Fan venturis or surrounds are important to the flow and adapting them to rectangular duct work requires larger plenums.

Sensors and actuators

The fastest growing technology

The progress of Sensor Technology over the last 5-10 years has created one of the fastest growing markets we have ever known. Humidity sensor ICs will not only renovate existing applications such as weather stations, but also create new areas of usage. Imagine condensation level monitoring or compensation of air moisture influence on any process or measurement. Inductive Sensors, a completely new category, are inductance-to-digital converters. The sensor can be a wound wire, a coil on a PCB, a coil printed with conductive ink on a flexible substrate, or even a simple spring. Measuring any proximity, metal comparison, movement, rotation, eddy current loss, positions, spring compression, -extension, -twist: the 24-bit L-resolution means sub-micron sensitivity. A new idea for all markets, for a reasonable price. New ways of optical proximity sensing, such as high speed image sensors for industrial applications, extremely linear working microphones, are already in mass production and available today.