What is the purpose of a calibration certificate? The calibration certificate is the official document registered for the calibration of instruments and provides traceability to the National Institute of Standards and Technology. The accuracy and integrity of the calibration certificate reflect the validity and credibility of the calibration organization. This document specifies the general requirements …
The Data Highway and Data Highway plus systems are Local Area Networks (LANs). They connect programmable controllers, computers, and other devices so they can communicate and exchange data with one another. A cable system is the physical means of transmitting this data between nodes. On DH and DH+ networks, a node is a hardware interface. …
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Inverse Time Circuit Breakers Inverse time circuit breakers have both thermal and instantaneous trip features and are preset to trip at standardized levels. This is the most common type of circuit breaker used in the building trades for residential, commercial, and heavy construction. The thermal action of this circuit breaker responds to heat. If a …
Profibus ProfiBus (PROcess FIeld BUS) is a widely accepted international networking standard, commonly found in process control and in large assembly and material handling machines. It supports single-cable wiring of multi-input sensor blocks, pneumatic valves, complex intelligent devices, smaller sub-networks (such as ASi), and operator interfaces. It is an open, vendor independent standard. It adheres …
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Industrial Ethernet Early Ethernet systems (of the 10 Mbps variety) use the CSMA/CD access method. This gives a system that operates with little delay if lightly loaded, but becomes very slow if heavily loaded. Ethernet network interface cards are relatively cheap and produced in vast quantities. Ethernet has, in fact, become the most widely used …
Example calculation: controller output to valve An electronic loop controller outputs a signal of 8.55 mA to a direct-responding control valve (where 4 mA is shut and 20 mA is wide open). How far open should the control valve be at this MV signal level? We must convert the milliamp signal value into a percentage …
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Main pneumatic components All main pneumatic components can be represented by simple pneumatic symbols. Each symbol shows only the function of the component it represents, but not its structure. Pneumatic symbols can be combined to form pneumatic diagrams. A pneumatic diagram describes the relations between each pneumatic component, that is, the design of the system. …
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Introduction The construction and mechanical operation of all types of pressure spring thermometers are identical. The thermal system of pressure spring thermometer contains a metal bulb, capillary and receiving element. Metal bulb contains a thermometer fluid, a liquid or a gas or a liquid vapour and is inserted at the point at which the temperature …
Installation: After installation and before start up of the differential pressure transmitter, be sure to perform the following checks and procedures. Preparation: (1) Check for liquid or gas leakage of the process connection by applying soapy water or similar. (2) Check of the electrical connection according to the “Terminal block connection diagram (3) Vent the …
Filled impulse lines An alternate method for isolating a pressure-sensing instrument from direct contact with process fluid is to either fill or purge the impulse lines with a harmless fluid. Filling impulse tubes with a static fluid works when gravity is able to keep the fill fluid in place, such as in this example of a pressure transmitter connected …
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