What is Ratio Control ?
Most people reading this article have likely had the experience of adjusting water temperature using two hand valves as they took a shower: one valve controlling the flow of hot…
Ratio Controller Example
An example of ratio control at work is in a process whereby hydrocarbon gases (usually methane) are converted into hydrogen gas and carbon dioxide gas. This is known as the…
Thermocouple Calculations
The voltage generated by a thermocouple is a function of the temperature difference between the measurement and reference junctions. Traditionally the reference junction was held at 0 °C by an…
Liquid In Glass Thermometer Principle
The liquid in glass thermometer, is the most commonly used device to measure temperature and it is inexpensive to make and easy to use. The liquid in glass thermometer has…
How to Convert Cable Size from AWG to Inches
How to Convert Cable Size from AWG to Inches ? Here is the formula for conversion of cable size from American wire gauge to inches. The diameter of a Number…
Cascade Control
A simple control system drawn in block diagram form looks like this: Information from the measuring device (e.g. transmitter) goes to the controller, then to the final control device (e.g.…
Supervisory Control
In a manually-controlled process, a human operator directly actuates some form of final control element (usually a valve) to influence a process variable. Simple automatic (“regulatory”) control relieves human operators…
Tuning a Temperature Process Control Loop
Tuning a Temperature Process Control Loop Ziegler-Nichols open-loop tuning procedure This next simulated process is a temperature control process. Performing an open-loop test (two 10% increasing output step-changes, both made…
Tuning a Liquid Level Process Control Loop
Ziegler-Nichols open-loop tuning procedure The next simulated process I attempted to tune was a liquid level-control process. Performing an open-loop test (one 10% increasing output step-change, followed by a 10%…
Features of PID Controller actions
Purpose of each Controller action Proportional action is the “universal” control action, capable of providing at least marginal control quality for any process. Integral action is useful for eliminating offset…
