Pressure Switch A pressure switch is an ON/OFF device that activates (changes electrical contact) when the pressure reaches a preset setpoint. A pressure switch is a simple device that monitors pressure and turns ON/OFF a circuit when pressure reaches a set value. How it Works Pressure acts on a diaphragm or piston. When pressure crosses the setpoint, the internal NO/NC contact changes state. You set a pressure value (Setpoint). When the process pressure rises above or falls below that setpoint, the switch contacts change state (NO→NC or NC→NO). It gives only ON/OFF output. Output Type NO/NC Contact Relay Output Applications Pump start/stop (flow detection) High/low pressure alarm  Compressor control (gas pressure checking) Safety interlock (line pressure checking) Pressure Transmitter A pressure transmitter measures pressure continuously and s...

How to Calibrate a Pressure Transmitter — Step-by-Step Guide Pressure transmitter calibration ensures that the transmitter provides accurate readings of applied pressure by comparing it with a known reference standard. This is essential for process accuracy, safety, and reliability. Required Equipment Pressure Calibrator / Hand Pump / Dead Weight Tester – for applying known pressure. Digital Reference Gauge – for precise measurement accuracy. 24 V DC Power Supply – to power the transmitter. Multimeter / Loop Calibrator – to measure 4–20 mA output signal. HART Communicator – for SMART transmitters. Tubing and Fittings – for proper connection and sealing. Working Principle A pressure transmitter converts the applied pressure into a proportional electrical signal (4–20 mA) . Typically, 4 mA represents 0% (LRV) and 20 mA represents 100% (URV) of the calibrated pressure range. Calibration Procedure Step 1: Isolate ...

What is a Gas Filled Dial Thermometer? Essentially, the gas-filled dial thermometer is a measuring principle based on the volumetric temperature expansion of the gas filling in the measuring element. The measuring element is tightly connected by a capillary tube containing a measuring spring. The spring transfers the expansion of the gas filling through the movement on the dial. Gas-filled dial thermometers are used for temperatures ranging from -80°C to +600°C. The accuracy is ± 1% of full scale deflection. A gas-filled dial thermometer can be supplied with a capillary line between the measuring element and a 100 m long spring.

What is a Bimetallic Dial Thermometer? A bimetallic dial thermometer is basically a measuring element that consists of two, metal tapes, joined together. Tapes with different thermal expansion coefficients. The coiled measuring element is fixed at the end of the stem; The other side is attached to a pointer axle. Temperature changes cause the bi-metal to stretch or bend, causing the coiled component to twist. This movement is proportional to the temperature change and is shown on the dial. Bi-metal dial thermometers are used for temperatures ranging from – 50°C to +500 C. The accuracy is ± 1,6% of full scale deflection.

What is an absolute pressure gauge with a diaphragm? Basically, an absolute pressure gauge with a diaphragm in this type of gauge is used to measure pressure, independent of any changes in ambient pressure. The pressure chamber shall be isolated by a thin diaphragm. A chamber that will not be loaded to gauge pressure, will be evacuated to absolute vacuum. This vacuum (= absolute zero-point) is called the reference pressure. The diaphragm will be loaded with measuring pressure and will flexibly deviate from its normal position, thus transmitting the pressure through the bellows upon movement. Absolute pressure gauges are used for measuring gases and liquids; It can be aggressive too. The accuracy is ± 1,6% of full scale deflection. Basically, an absolute pressure gauge with a diaphragm in this type of gauge is used to measure pressure, independent of any changes in ambient pressure. The pressure chamber shall be isolated by a thin diaphragm. A chamber that will not be loaded to gauge pr...

What is Differential Pressure Gauge? Basically, differential pressure means that the pressure chamber will be separated by a thin diaphragm. This diaphragm is under constant pressure from both chambers and additionally has a gauge pressure from one chamber. The diaphragm will transmit pressure differences through the bellows on movement. The movement shows a positive or negative value on the dial with a 270° angle. The bellows on the opposite side compensates the force. Differential pressure gauges are used for measuring gases and liquids; It can be aggressive too. The accuracy is ± 1,6% of full scale deflection. The ambient temperature should be from -20 to +60 °C; and medium temperature not exceeding +100°C.

What is chemically sealed Bourdon tube pressure gauge? Basically Borden tube gauge will be fixed on the seal. A seal consists of a defined cavity that is closed off with a thin, flexible diaphragm. The volume between this diaphragm and the Borden tube will be filled with transmission fluid after it has been completely emptied. When pressure is applied, a flexible diaphragm will use this fluid to transmit the applied pressure, thus lifting the gauge. A Borden tube transfers the measured pressure using movement on a dial with a 270° angle. As the liquid fills, the connection between the seal and the gauge should remain closed. The seal can be made in various forms and types. The gauges with seals can be used to measure pressure from -1 bar to 1000 bar. The accuracy is ± 1,0% of full scale deflection. Sealed gauges are mainly used outdoors as there is no risk of freezing. The gauge with connecting flange is suitable for highly viscous, crystalline and medium solid materials. Flat seals ma...

What is a capsule pressure gauge? Basically the capsule consists of two thin, concentrically corrugated diaphragms welded or attached together. The pressure change in the capsule causes elastic deformation on both sides of the measuring element. The travel of the measuring element is proportional to the pressure being measured. It will be transmitted to a pointer using a geared movement and indicated on a dial with a 270° angle. Capsule pressure gauges are used for measuring low positive or negative values up to 600 mbar. The accuracy is ± 1,6% of full scale deflection. Capsule is made of Brass or SS316. and is only used to measure gases. And this ambient temperature will be -20 +60 °C; The medium temperature shall not exceed +100°C.

What is a diaphragm pressure gauge? Basically a diaphragm pressure gauge, the concentrically corrugated diaphragm would be fixed between two flanges. The diaphragm will be loaded by the process pressure on one side and will flexibly deviate from its normal position. This path is proportional to the pressure applied and will be transmitted in a rotary geared movement. The movement has a pointer and shows pressure on the dial with a 270 angle. Diaphragm pressure gauges are used to measure the pressure of gases, vapors and liquids from 40 bar and vacuum to -1 bar. The accuracy is ± 1,6% of full scale deflection. Tantalum, Hastelloy C etc. Or the diaphragm can be protected from aggressive media by using a PTFE-coated foil. The connecting part can be made or protected with suitable materials, ie SS 316L, PP, PVC, PVDF etc. Diaphragm pressure gauges with open measuring flanges are perfectly suited for media containing highly viscous, crystalline and solid substances. Diaphragm pressure gauge...

What is Bourdon tube pressure gauge? Basically Bourdon tube pressure gauges will have flexible (circular) measuring elements soldered or welded into sockets; The free end is closed tightly. The change in pressure causes the deflection of the measuring element. This deflection of the free end of the Borden tube is proportional to the applied pressure and is transmitted in a rotary geared movement. This movement carries a pointer and indicates pressure on the dial with a 270° angle. Bourdon tube gauges are used to measure high pressures up to 1000 bar and vacuums of gases, vapors and liquids down to -1 bar. The accuracy is between ± 0,1% and ± 2,5% of full scale deflection. In case of aggressive media, Borden tube can be made of brass, stainless steel or Monel.

What is the use of pressure switch?  A pressure switch is used to detect low pressure condition or high pressure condition.

  Well type Manometer   The well type monometer is widely used because of having only one leg.  The main difference between a U-tube manometer and a well type manometer is that the U-tube is substituted by a large well such that the variation in the level in the well will be negligible and instead of measuring a differential height, a single height in the remaining column is measured. It consist of a large diameter vessel with one side connected to very small size tube, so that the zero level moves very little when the pressure is applied. The area of well is much greater than the area of tube. In general this ratio is greater than 10. Accuracy is achieved by setting zero level of well at zero level of scale before each reading of table. The sensitivity of such monometer is good. Well Manometer Principle Well Manometer same as the U-tube except for the reservoir on the high-pressure side. It is sometimes called a single column gauge. The manometer consists of a meta...

  monomers Manometer is a device used to measure pressure at a single or multiple points in a single or multiple pipelines, by balancing the fluid column by the same or another column of fluid. Manometers work by the principle that a column of fluid in a tube will rise or fall until its weight is in equilibrium with the pressure differential between the two ends of the tube. For a pressure difference P is the height difference h between the level of liquid in the two halves of the tube A and B, is given by the equation P = pgh, where p is the density of the fluid in the tube. U-Tube Manometer “A U-tube manometer, in which differential pressure is measured as the difference 'h' between the high-pressure reading and the low-pressure reading, multiplied by the density of the liquid in the tube.” The difference in height of the liquid represents the applied pressure. In U-tube manometer we measure the pressure as: P= sp wt * height( fluid)- sp wt * height( Hg) Introduction...

  Bourdon Tubes Bourdon Tubes are known for its very high range of differential pressure measurement in the range of almost 100,000 psi (700 MPa). It is an elastic type pressure transducer. The device was invented by Eugene Bourdon in the year 1849. The basic idea behind the device is that, cross-sectional tubing when deformed in any way will tend to regain its circular form under the action of pressure. The bourdon pressure gauges used today have a slight elliptical cross-section and the tube is generally bent into a C-shape or arc length of about 27 degrees. The detailed diagram of the bourdon tube is shown below. As seen in the figure, the pressure input is given to a socket which is soldered to the tube at the base. The other end or free end of the device is sealed by a tip. This tip is connected to a segmental lever through an adjustable length link. The lever length may also be adjustable. The segmental lever is suitably pivoted and the spindle holds the pointer as shown in t...

  Pressure Measurement   This module will examine the theory and operation of pressure detectors (bourdon tubes, diaphragms, bellows, forced balance and variable capacitance). It also covers the variables of an operating environment (pressure, temperature) and the possible modes of failure. General Theory   Pressure is probably one of the most commonly measured variables in the power plant. It includes the measurement of steam pressure; feed water pressure, condenser pressure, lubricating oil pressure and many more. Pressure is actually the measurement of force acting on area of surface.  We could represent this as:  Pressure = Force/Area or P=F/A The units of measurement are either in pounds per square inch (PSI) in British units or Pascals (Pa) in metric. As one PSI is approximately 7000 Pa, we often use kPa and MPa as units of pressure. Pressure Scales   Before we go into how pressure is sensed and measured, we have to establish a set of ground rules. Pr...

Pressure Measuring Devices Pressure  Pressure is the force acting per unit area and it is expressed mathematically as pressure equal to the force divided by the area and the unit of pressure is newton per meter squared and newton per meter squared is also called pascal. And common types of pressure are atmospheric pressure, absolute pressure, vacuum pressure, gauge pressure. Common units of pressure are pascal, kilogram per square centimeter, bar, pound per square inch or psi, mmh2o, mmhg, inh2o, inhg. P = Force(F)/ Area(A) , pascal (N/m²) Pressure measuring devices Pressure measuring instruments are barometer, manometer, pressure tube, diaphragm pressure gauge 1. Barometer A barometer is a device that measures atmospheric pressure and common types of barometers are digital barometers, water barometers and mercury barometers. 1. Digital Barometer Digital barometer is the most common barometer for measuring pressure and Digital barometer is used for micro chip or IC to measure air p...