Tag: instrumentation
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Instrument Installation – Mounting & Accessibility Guidelines
Before we look at the instrument installation – mounting and accessibility guidelines, it is important to ensure that installation is carried out using the best engineering practices by skilled professionals in Instrumentation and Control, Electrical, Industrial Automation, etc. These professionals should be fully conversant with the safety requirements and regulations governing a plant site. Generally…
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PLC Instruction Set
An Overview of PLC Instructions Types There are various types of instructions that are available in a PLC. The instruction set will vary depending on the brand and type of processor you are working with. For example, the classic Allen-Bradley PLC-5 has 9 types of instructions: Bit Level Instructions This is the most common instructions…
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Demand Mode vs. Continuous Mode Safety Function
Demand Mode Safety Function Demand mode safety function is where a specified action is taken in response to process conditions or other demands. In the event of a dangerous failure of the SIF, a potential hazard only occurs in the event of a failure of the process of BPCS (Basic Process Control System). Demand mode…
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How to Calibrate an AC Ammeter & an AC Voltmeter
An instrument calibration is performed by comparing its reading with that of a more accurate instrument when both instruments are measuring the same quantity. In this case, the more accurate instrument is employed as a standard for comparison purposes. To calibrate ac ammeters and ac voltmeters, ac supply and an ac standard instrument must be…
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The IEEE-488 Instrumentation Bus (GPIB)
A bus in computer systems means a collection of unbroken signal lines that interconnect computer modules; these connections are usually made by taps on the lines. Examples of parallel bus architectures and protocols include: IBM PC bus (IBM PC/XT/AT), the Intel iSBX bus, the MicroVAX Q-bus, the Intel Multibus (IEEE-796 bus), the IEEE-488 instrumentation bus…
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What are Virtual Instruments?
Virtual instruments (VI) are instruments based on computer software whose controls and displays are presented on a computer screen and whose operation and settings are controlled by the keyboard and mouse. Instead of purchasing a number of expensive, dedicated, standalone instruments, users find it less costly to purchase a computer with a multichannel, analog-to-digital converter…
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Instrument Piping Systems Installation Guidelines
The right installation ensures the long term instrument system reliability. In this article we look at the general guidelines for the installation of instrument piping systems. Piping Systems/Tubing Runs Before we can proceed, it is important to state the difference between piping and tubing; tubing can be regarded as thin-walled seamless pipe that cannot be…
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What is Calibration of the Sensor?
Calibration of the sensor is the relationship between the physical measurement variable input and the signal variable output for that specific sensor. Typically, a sensor or an entire instrument system is calibrated by providing a known physical input to the system and recording the output. The data is plotted on a calibration curve such as…
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How HAZOP Technique is used to identify Hazards in a Process
In functional safety, hazards are events which have the potential to cause harm such as personal injury, damage to the environment or the business. Hazards in the process industry might include: the pressure of liquid in a vessel (high pressure may result in loss of containment, leaks or vessel rupture), the level of liquid in…
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Safety Function in a Machine Control System
A safety function is executed by the safety-related parts of the machine control system to achieve or maintain the equipment under control in a safe state with respect to a specific hazard. A failure of the safety function can result in an immediate increase of the risks of using the equipment; that is, a hazardous…