PROXIMITY SENSOR

 

A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact.
A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for inst...ance), and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. Different proximity sensor targets demand different sensors. For example, a capacitive photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor always requires a metal target.
The maximum distance that this sensor can detect is defined "nominal range". Some sensors have adjustments of the nominal range or means to report a graduated detection distance.
Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between sensor and the sensed object.
Proximity sensors are also used in machine vibration monitoring to measure the variation in distance between a shaft and its support bearing. This is common in large steam turbines, compressors, and motors that use sleeve-type bearings.

circuit for controlling a lamp from two places

Why Aren’t Bird Electrocuted When They Perch On Power Lines?

 

It’s not unusual to see lines of birds perched on power lines. But did you ever wonder why birds aren’t electrocuted by the currents that flow through these high-voltage wires?
Yo...u might think it’s because the wires are insulated, but they’re actually not insulated at all — that’s why downed power lines are so dangerous. No, the only reason why birds on power lines usually aren’t electrocuted is because the wire is the only thing they’re touching!
Why No Zap?
Like all energy, electricity seeks equilibrium, or balance. That means electricity will flow fromhigh-energy areas to areas of less energy, always using the path of least resistance. So if the bird has one foot on our original wire, and the other foot on, for example, the ground or on a different wire with less voltage, the bird would be electrocuted. The electricity would pass through the bird on its way from the high-voltage line to the lower-voltage line or the ground.
But as long as both of the bird’s feet are on the same wire (or wires of the same voltage), the bird is safe. The current doesn’t have anywhere else to go, so the electricity won’t pass through the bird–it stays on the path of least resistance, the wire.

Advantages of 3phase power over 1phase power

Three phase power transmission has become the standard for power distribution.Three phase power generation and distribution is advantageous over single phase power distribution.

Three phase power distribution requires lesser amount of copper or aluminium for transferring the same amount of power as compared to single phase power

The size of a three phase motor is smaller than that of a single phasemotor of the same rating.

Three phase motors are self starting as they can produce a rotating magnetic field. The single phase motor requires a special starting winding as it produces only a pulsating magnetic field.

Three phase power transmission has become the standard for power distribution. Three phase power generation and distribution is advantageous over single phase power distribution.

In single phase motors, the power transferred in motors is a function of the instantaneous current which is constantly varying. Hence, single phase motors are more prone to vibrations. In three phase motors, however, the power transferred is uniform through out the cycle and hence vibrations are greatly reduced.

The ripple factor of rectified DC produced from three phase power is less than the DC produced from single phase supply.

Three phase motors have better power factor regulation.

Motors above 10HP are usually three phase.

Three phase generators are smaller in size than single phase generators as winding phase can be more efficiently used.

 

Calibration Explained

To prove all instruments measuring ability which is reliable and accurate, the results of measurement are to be compared with higher standard instrument of the same kind. The procedure of this is termed as Calibration.

Calibration is done by a sequence of measurements on the device under test (DUT) to a Universally (International/ National) accepted as reference standards. To execute the calibration, the technician takes measurements of several points ranging from zero to full scale and back to zero. For ex, in a pressure gauge calibration, we use pressure source such as hand pump, calibration manifold, volume controller and nitrogen gas to create the pressure necessary to take the sequence of measurements. we use pressure calibrator or pressure test gauge as our reference. once the sequence of measurements are taken, they are compared to the reference standards. 

In the oil and gas industry, pressure and temperature transmitters re very very important. By measuring temperature, pipeline pressure and pressure drop across a restriction (called an Orifice Plate) we can infer the flow of oil or  gas through the pipe at a given time.

What is an instrument?

An instrument is a device that measures and control the physical process include pressure, temperature, flow rate and chemical consistency. 

Difference between Analog Signal and Digital Signal?

Due to the fact that electrical quantities of voltage and current  are able to easily control, manipulate and transmit over long distance, they are widely used to represent the physical variables and transmit the information to the remote locations. 

A signal is any kind of physical quantity that conveys information. Audible speech is certainly a kind of signal, as it conveys the thoughts (information) of one person to another through the physical medium of sound. Hand gestures are signals, too, conveying information by means of light. This text is another kind of signal, interpreted by your English-trained mind as information about electric circuits. In this chapter, the word signal will be used primarily in reference to an electrical quantity of voltage or current that is used to represent or signify some other physical quantity.

Analog signal
Simply we can say,a signal which varies continously with time.From the real world itsel we can found out so many examples for analog signals.sound,light etc..But in the case of instrumentaton we are using 4-20 ma or 0-20 ma as analog signals.Here the voltage between controller and instrument is kept constant and taking the current as signal.

Digital signal
Digital signal is discrete to time. Actually digitally signal is sampled from analog signal.In the conventional method they use two discreet levels for transmitting the signal from instrument to controller. Logic high And Logic low. Relays are used for implement the digital signal transmission. Recently, different types of digital signals are introduced for communication between instrument and controller. Some signals are Profibus, HART, FieldBus. I will explain about each signals in my coming posts.

What is instrumentation engineering?

          Instrumentation is the vast multi-disciplinary branch of engineering that comprises of Electrical, Electronics, Mechanical, Computer Science and Communication in it. Instrumentation engineering deals with measuring, monitoring & controlling various processes in industries and other automation sectors. Hence instrumentation field plays an important role in modern industries that requires high productivity, better quality and improved safety. 

         An instrumentation engineer is responsible for the design, construction and maintenance of entire monitoring and control systems such as sensors, motors, valves, actuators, robots etc. 

 Core Subjects:

Sensors and  Transducers

Control Systems and Process Control

Microcontrollers, PLC, DCS, SCADA, VFD, HMI

Signal Conditioning Circuits

Industrial Instrumentation

Instrumentation System Design

Electrical Machines and Power Converters

PC interfacing and Telemetry

Robotics