There are several temperature element instrument types widely used to measure temperature of a process substance . These types are categorized into mechanical temperature element and electronic temperature element. Mechanical temperature element uses the principle of thermal expansion i.e. the element expands if the temperature rise and vice versa. Electronic temperature element use the principle of electrical properties change following of temperature variation. Read More..
Tubing Schedule is a document containing list of instrument tubings which serves as impulse line, hydraulic/pneumatic supply and return line, process tubing such as chemical injection line, fusible loop. This document also shows details of tubing required for connecting between two points. Read More..
Why the cable screen shall not be grounded at instrument field device?
Cable screen protects the signal carried on the conductor from external interference. Cable screen blocks the external interference and noise, then directs it to the ground.
Screen shall only be grounded at one source. The grounding is usually made in equipment panel or cabinet while field device point is left ungrounded and insulated. This is to eliminate the ground-loop current that may arise if screen is grounded at both end. In this case, the ground loop current becomes a noise for the signal conductor itself. Read More..