Author: John Mulindi
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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 RS-232, RS-422 and RS-485 Networks are applied in Instrumentation
RS-232 Presently, this standard is known as TIA-232C. These are point-to-point networks with a purpose of connecting only two devices. The signaling is single-ended (unbalanced) which implies that the respective voltage pulses are referenced to a common ground conductor and a single conductor is used to transfer data in each direction as illustrated in figure…
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Basic Features of Foundation Fieldbus (FF)
Foundation fieldbus (FF) and Profibus are the two most universal serial data bus formats that are used for interfacing between the central processor and smart devices in the process control system. The Foundation Fieldbus is mainly used in U.S. while Profibus format is primarily used in Europe. A serial data bus is a single pair…
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Radio Frequency (RF) and Microwave – Multiple Choice Questions & Answers (MCQ3)
The Answers have been provided at the end of Questions. Q1. What is the approximate bandwidth of radio frequency (RF) electromagnetic waves? A. 300 Hz to 300 GHz B. 20 Hz to 20 kHz C. 300 Hz to 3000 GHz D. 300 MHz to 300 GHz Q2. In spectral analysis the following factors are considered…
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How Ground Fault Interrupter (GFI) is used as a Safety Device
The function of a ground fault interrupter (GFI) is to disconnect the power if a current leakage to ground is detected. GFI is also termed to as Ground fault circuit interrupter (GFCI). We have two types of ground fault interrupters: those designed for life protection and those designed for equipment protection. GFI used for life…
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Features of Stepper Motors & How they are applied in Industrial Control
A stepper motor is a permanent magnet or variable reluctance DC motor that has the following characteristics: It is able to rotate in both directions It can move in precise angular increments It can sustain holding torque at zero speed Can be controlled with digital circuits Stepper motor moves in accurate angular increments, known as…
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Single-phase and Three-phase Power Systems
Single-phase Power System To help us understand single-phase power system, consider the sine wave shown in figure 1(a) below of a 120 Vac single-phase power connected to a plug. We know very well that, voltage is the difference in potential between two points. Therefore the sine wave in figure 1(a) shows only the voltage difference…
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Types of Resistors
Resistors perform two basic functions in a circuit: they limit current flow and set voltage levels within a circuit. We have various kinds of resistors e.g. fixed resistors, variable resistors, digitally adjustable resistors, photoresistors, fusible resistors, etc. Generally, resistors can be broadly categorized as: Fixed Resistors Fixed resistors are those whose value cannot be changed…