Tag: instrumentation and control
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Features of HART Communication Protocol
HART is an acronym for (High Addressable Remote Transducer). HART is implemented in two ways in industrial instrumentation networks: Point to point system Multidrop system HART Point to Point System Here serial communication data is superimposed onto a standard 4-20 mA loop signal as shown in figure 1(a): Frequency shift keying (FSK) is used with…
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How to Connect a DP (Differential Pressure) Flow Sensor to a DP Transmitter
The DP Transmitter should be mounted with a manifold block as illustrated in the figure 1(a) below to allow for maintenance. Valves B and C are the isolation valves while valve A is an equalizing valve. Valve A is used along with valves B and C to zero the transmitter. In normal operation valve A…
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Instrumentation Sensors and Transducers – Multiple Choice Questions & Answers (MCQ4)
The Answers have been provided at the end of the Questions: Q1. Which of the following sensors is used to measure displacement? A. Thermistor B. LVDT C. Dall tube D. None of the above Q2. Which of the below listed sensors is used for temperature measurement? A. Strain gauge B. Thermistor C. Piezoelectric crystal D.…
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How Signal Processing Circuits are protected from high currents & voltages
Protection against high currents and voltages is a very important requirement for signal processing circuits. A high current can be protected against by the incorporation in the input line of a series resistor to limit the amount of current flowing to an acceptable level and a fuse to break if the current exceeds a safe…
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How to Tune the PID Controller
Before we discuss how to tune the PID controller, let’s look at some basic facts about PID Controller. Basic Facts about PID Controller Many control systems use a combinational of three types of control i.e. Proportional + Integral + Derivative (PID) control. The foundation of the system is the Proportional Control, adding Integral Control provides…
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Methods of Protecting Instruments from Explosive Atmospheres
The protection method used in a specific hazardous location depends on the application, the technology available and the specific explosive atmosphere present. In this article, we discuss the following methods of protection: Table 1 provides the summary information for each protection method. The codes are used in the markings or labels for apparatus and enclosures.…
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Functional Safety in Instrumentation Systems (SIS, SIF & SIL)
Functional safety is the risk reduction provided by the functions implemented to ensure the safe operations of the process. The IEC 61508 standard covers functional safety of electrical/electronic/programmable electronic safety-related systems. The purpose of IEC 61508 is to use safety instrumented systems that reduce risk to a tolerable level by following the overall hardware and…
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4-20 mA Transmitters (2-wire, 3-wire and 4-wire Types)
Background of 4-20 mA Signal Transmission Initially signal transmission was dominated by pneumatics before the advent of 4-20 mA signal standard. The standard was 3-15 psi pneumatic signal where the 3 psi was the ‘live zero’ and 15 psi represented the 100 %. Any pressure below 3 psi was considered ‘dead zero’ and an alarm…
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What is a Smart Sensor?
A smart sensor is the integration of a sensor with an analogue to digital converter (ADC), a processor and digital to analogue converter (ADC) for actuator control. A typical application of a smart sensor set up is a temperature control of a furnace as illustrated below. The electronics in the smart sensor contains all the…
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P&IDs and Loop Diagrams
Process and Instrument Diagrams (P&IDs), also called Piping and Instrumentation Diagrams and Loop diagrams are construction and documentation drawings that show the flow of the process and illustrate the instrumentation control and measurement instructions, wiring and connections to the process. The sections or subsystems of the process that are usually shown are called loops. A…