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Control and Instrumentation Glossary

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To confirm the initial calibration has not changed and is still valid.
Validation is usually performed at regular intervals
Further Reading


Velocity Collar
A collar fitted to a thermowell to reduce the suspended length of the well in the pipe.
Its use reduces vibrations induced by wake shedding.
Further Reading


Very Early Smoke Detection and Alarm
Trade name which has become synonymous for all types of aspirating smoke detection systems.
Further Reading


VFD - Variable Frequency Drive
An electrical system that allows a motor to be controlled to run at different speeds.

Further Reading


A measure of a fluid's resistance to flow.

Further Reading
Viscosity Toolbox Page

VPN - Virtual Private Network
The use of encryption to provide a secure connection through an otherwise insecure network e.g. typically the Internet.
The encryption may be performed by firewall software or possibly by routers.
Further Reading


VSD - Variable Speed Drive
An system - either electrical or mechanical - that allows a motor to be controlled to run at different speeds.

Further Reading


Notified Body based in Finland

Further Reading


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C&I Resources

Cable Gland Selector
CE Marking
Flange Dimensions
Ingress Protection
Pipe Schedules
Relief Valve Orifice Size
Temperature Class
Temperature Conversion
Thermocouple Types
Valve Leakage
Vortex Meters
Wires and Cables


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