Four Electrode Conductivity Probes Principle
A very old electrical technique known as the Kelvin or four-wire resistance-measuring method is a practical solution to the problem of electrode fouling faced by two-electrode conductivity probes. Commonly employed…
Two Electrode Conductivity Probes Principle
We may measure the electrical conductivity of a liquid solution by passing an electric current through it. The most primitive form of conductivity sensor (sometimes referred to as a conductivity…
Conductivity Measurement
The electrical conductivity of liquids is an important analytical measurement in many industrial processes. This measurement is one of the more non-specific types of analytical technologies, because it does not…
Accelerometer Vibration Probe Principle
In simple language we say that vibration is a movement or mechanical oscillation about an equilibrium position of a machine or component. Vibration is a by-product of an otherwise useful…
Determining the Design Purpose of Override Controls
Override control strategies are a source of much confusion for people who first learning the concept. Perhaps the most fundamental question people find difficult to answer when faced with an…
How to Analyze a Cascade Control Loop?
Let us discuss a steam-heated reactor control system with a cascade strategy, where the temperature controller drives a setpoint signal to a “slave” steam flow controller: Cascade Control Loop In…
How to Analyze PID Controller Actions
The direction of action for a loop controller – either direct or reverse – at first seems like a very simple concept. It certainly is fundamental to the comprehension of…
Override Control Functions
An “override” control strategy involves a selection between two or more controller output signals, where only one controller at a time gets the opportunity to exert control over a process.…
Selector Control Functions
In the broadest sense, a “selector” control strategy is where one signal is selected from multiple signals in a system to perform a measurement control function. I will use the…
Limit Controls : High Limit & Low Limit Functions
A common application for select and limit functions is in cascade control strategies, where the output of one controller becomes the setpoint for another. It is entirely possible for the…
