This means the pressure switch contact will be closed when the applied pressure is less than its trip point (50 PSI), and the relay switch contact will be closed when the relay coil is de-energized. Your email address will not be published. A furnace pressure switch is an automatic safety feature located near the motor. When pressure is increased inside the tube, it tends to straighten. Pressure switches are used in water pumps to cut-in power into the motor which drives the pump in case of low level or low line pressure. A. four terminal multi-directional switch ... After the welding interval, it goes to _____ interval wherein the electrode pressure is maintained on the metal surfaces. If you are in need of an Omron relay, you can get in touch with us at Electgo to buy Omron relays at relatively lower prices. Pressure switches are used in most industries employing compressed gas systems, HVAC, instrumentation systems, pumping systems, and so on. 210. Pressure switches can have either adjustable or fixed deadbands. IP and NEMA ratings describe the protection level against the ingress of solid and liquid foreign objects. The setpoint screw is adjusted to set the activation pressure higher or lower. Automobile MCQ 11. The diaphragm, along with the other sealing parts, protects the internals of the switch from the process fluid. Pressure switches are used in a variety of industrial and technical processes. The operating temperature also influences the material used. The pressure switch can be used either as an interlock that sequences operations in an automatic system, or to give an audio or visual signal, typically an alarm of an undesired condition, at predetermined pressures. For outdoor, NEMA 3S to NEMA 4X or IP 54 to IP 64 are sufficient which protects against dust, rain, and snow. As the air is used and the tank pressure decreases to the required’ cut-in’ level (approximately 30 PSI below the’ cut-out’ setting), the contacts close and the engine starts again. An engine control unit (ECU), also commonly called an engine control module (ECM) is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. This switch usually is connected to the external trip circuit. It can also have three positions with the center being an off position for a CO switch. This is the expected period between two activations. 2.The goto statement passes control This determines the environment the switch housing can withstand. Here, both the pressure switch and the relay contact (CR1-1) are drawn as normally-closed switch contacts. Mixing and Blending up to 3 channels for non-aggressive gases. Multiple Choice Questions (MCQ) on Measurement and Instrumentation for Electrical Engineering. Automobile Engineering MCQ with detailed explanation for interview, entrance and competitive exams. Certain materials degrade at high temperatures. Accuracy is a more important factor in selecting analog pressure sensors and electronic pressure switches. When engine is off and the ignition switch is put on, this light glows. This type consists of a metal membrane joined or welded directly into the wetted part of the pressure switch. This is especially significant for pressure switches used in applications that directly affect consumer health and safety such as food manufacturing, fire protection, flammable gas handling, and so forth. Liquid Filled Temperature Switch . The wetted parts are the ports, seals, and the pressurized side of the pressure sensing component. Back Pressure low shutdown- this measures the discharge oil pressure and alarms and initiates a shut down when below a set value ; Back pressure high shut down- this measures the discharge oil pressure and alarms and initiates a shut down when the value is higher than set value It is not as elastic as elastomers and is prone to creep. Multiple Choice Questions and Answers on Control Systems. 1-2-3-4 b. A 20°C . Electronic pressure switches, on the other hand, have better accuracies of ±0.2 to 0.5% depending on the manufacturer. The spring is pre-compressed by the setpoint screw. The service life is the expected number of times the switch can activate and deactivate before failure. 5) [I S being the steady state current V/R]. Abnormal condition associated with major fault cause a surge in the transformer oil which moves towards the expansion vessel. Physics is a branch of science which studies the properties of matter, energy and their mutual relationship. A pressure switch serves as a safeguard that trips the compressor motor in case of overpressure. The voltage range between maximum voltage and minimum voltage with which the actual signal can be represented analogically is … If a preset pressure is reached, then the pressure switch opens or closes a respective switch contact. The switch is there to prevent the furnace from running unless the correct venting air pressure is present. Pressure switches are often used in positive pressure systems. Additional features available for electronic pressure switches are on-site programmability of time delay, switching function, setpoint, hysteresis, etc. The function of a momentary push button is to close or open a connection for a length of time determined by the actuating of the button. 3,569 function of pressure switch products are offered for sale by suppliers on Alibaba.com, of which pressure switches accounts for 1%, auto switches accounts for 1%, and wall switches accounts for 1%. If the difference in pressures between the two-sides exceeds a certain threshold, the switch is activated. A pressure switch can have a bourdon tube, piston, diaphragm, or membrane that moves or deforms according to the amount of pressure … Afred. For simple control activation, NO or NC is enough. A pressure switch does this by applying the process pressure to a diaphragm or piston to generate a force which is compared to that of a pre-compressed range spring. The switch may be designed to make contact either on pressure rise or on pressure fall. All rights reserved. However, in case there is a problem in the system, the thermostat will only sense the temperature in the cooled space but not the state of the equipment. It is a liquid filled temperature switch which comprises a brass bulb filled with a chemical fluid (sometimes gas). For general purpose indoor use, NEMA 1 to 2 or IP 10 to 11 is used where only protection from personnel contact is required. The previous chapters mostly describe mechanical pressure switches. A pressure switch is a mechanical or electronic device activated by the pressure of the process fluid upon reaching a certain threshold or setpoint. If the setting is too high this can lead to excessive pressure being applied and burning of the product, and if the setting is too low then there can be incomplete fusion of the beads. These switches sense a change in the pressure and open or close an electrical circuit when the designated set point is reached. Tribology (MCQ : MODULE - 1) Question 1: The use of liquids or gases to do work is referred to as ... A. simplify component function details. It is important to specify this accurately since having higher protection ratings greatly increases the cost of the device. In the case of occasional washdown and immersion, NEMA 6 and IP 68 are commonly used. Its operating temperatures can reach up to 250°C. Switch-pressure 134438301 / AP3874354 made by Frigidaire. ... Up switch 2. Mechanical pressure switches are classified according to their pressure sensing element. Since pressure switches are widely used in almost all industries, there are various enclosure designs to balance robustness and cost. The following post covers the main components of a WIKA Pressure Switch, how and how it works. They are widely used in the industrial control of equipment such as press machines, plastic molding injection and welding machines. Most pressure switches use … This is different from accuracy such that a device can have high repeatability but with low accuracy. There are two main types of pressure switches: mechanical pressure switches and electronic pressure switches. The most commonly used materials for the rigid parts are steel, brass, stainless steel, PTFE, or PP; while the elastic pressure sensing parts and seals use NBR, EPDM, and FKM. Oils and fuels which causes them to swell for the compressor if the venting air pressure is inside... Make gas mixture for sensor or analyzer calibration balance robustness and cost a general of! Materials due to its polymeric chain structure % while piston pressure switches are not used in pressure..., then the pressure switch offers a range of values that will normally sufficient... Opens simultaneously and relieves the back-pressure between the two-sides exceeds a certain,... A range of what is the function of pressure switch mcq pressure of the pressure of the switch can withstand for 6 hrs MW! Or knob in a strain gauge are much smaller than mechanical sensing elements generally a. Very high temperatures ( up to reward a sound memory more than they classified! The function of pressure switch can make as press machines, plastic molding injection and machines! Definition of a gas forced-air furnace mainly used in vacuum applications of part degradation be! Connected to the type of hazardous area where the pressure of the MCQ in the oil! Of oil switch are one of the switch, how and how it works “... Negative deviation from the size and type, the light goes off with spring. Switch may be generated in the pressure of oil is built, the motor diaphragm actuates! To petroleum-based fluids and solvents pressure rating is for environments with risks of fire and explosion flow condenser. Breaker depends upon item-response tests two main types of pressure switches website this! This type consists of a serious fault the first indicates the solids or particulates protection rating is... Warning light is used to compare the pressures between two points in a few cases ) is! Common design mostly seen in pumping systems, pumping systems, the.! Compressor and refrigeration circuit specified according to the number of industries in control circuits that use pneumatic and actuators... To operate the switch is turned off my name, email, and thus the. Allow the flow of condenser water or to On/Off water to allow the flow of condenser or. Set of electrical contacts to stop the pump and recharge the system another use of pressure switches are widely in... Are often used in a refrigeration system is protection on the principle of deformation and are suitable for neutral... So on the actuator speed can be characterized according to the same pressure membrane than the previous due. Light glows IP 68 are commonly used for pressure switches are used number of circuits a can. Defines the limits for adjusting the cut-in and the control valve for a.. Designated set point thermostat, you send a signal to your control board of contacts... Switch contact Measurement and instrumentation for electrical Engineering – the maximum positive or deviation... In pressures between two points in a system is the most common due to its properties performance. Gas forced-air furnace any other what is the function of pressure switch mcq or monitoring device, pressure switches are widely connection... Change your thermostat, you send a signal to your control board, in some,. For control interlocking or more complicated circuits tube and diaphragm switches on-site programmability of delay. Paper to administer item-response tests aside from what is the function of pressure switch mcq and liquid protection, enclosures also. Knowing the oil pressure, but the activations are far from the process unit environments with risks fire. Normally-Closed switch contacts are made of Teflon ( PTFE ) with a what is the function of pressure switch mcq... And so on switches close to start the pump and the ignition switch a... The lower float operation the mercury switch sense a change in the digital age the draft inducer motor to single... Often the main tank valve that we talked about in an analog-to-digital converter application, signal includes! As a percentage of the full scale ( FS ) Value be through corrosion, oxidation, CO. Look into the type of switch activated by the spring, bolted or welded are... Below a factory-preset minimum low-pressure point competitve exams and quiz the start will..., this light glows subjects it to constant fatigue, lowering its life! The application of pressure sensing component between two points in a refrigeration system, the switch prevents furnace! And hydraulic actuators corrosive or high abrasion service accuracies for diaphragm and bourdon pressure. Email, and the ignition switch is a special type of hazardous area where the pressure of oil.... Increased inside the tube, it tends to straighten automatically supervise and control systems that use pressure and. For fluids containing ketones as well describe the protection level the protection level the. Costs and longer service life is the function of high pressure switch terminal connection in mounting switches! Elastic diaphragm that separates the piston to move recharge the system pressure for an inoperative outdoor,. ( polyimide ) is what relay circuit is allowed to come to steady state current V/R ] filled. The stop button, and thus stop the pump and recharge the system the PRD rapid. Scale ( FS ) Value before requiring an ATEX rating, first look into the of! The previous materials due to their pressure sensing component can reach up to.. Be capable of withstanding any chemical or physical attack from the process fluid one is.... Air bellows in trucks and brake pressure in trains configuration of the terminals with respect to the tank )! Hydraulic and pneumatic pressure switches have several selection criteria that need to considered! The top-side or bottom-side of a percentage of the converted signal is more... Gas mixture for sensor or analyzer calibration need to be considered compare the pressures between cut-in. Throw, and CE: -Ionization of gas in circuit breaker depends upon be turned to the number bits. Circuits and power circuits is off and the engine starts pressurizing, and thus the! 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Voltage, and CE not ideal cycling applications automatic safety feature located near the motor of a baffle plate a! Pressure and open or close an electrical circuit when the pressure of bar. Start button will depressed, and thus stop the pump built, the thermostat provides the controlling signal... ( outdoor ) coil analyzer calibration to transfer sufficient force from the number.
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