Category Archives: Controls

Posts with information about control systems.

Learning about Relay Logic; What’s a Relay?

Author’s Note:  I edited this to put in pictures with better contrast for the relay images further down the post and for some reason, instead of just replacing the original post, the system put it up as a new post.   … Continue reading

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Control System Fundamentals

This post evolved to support a string of posts I will start next to support an exercise in one of the classes I am involved with at the Pacific Energy Center.  In those posts, we will look at how you … Continue reading

Posted in Controls, HVAC Fundamentals, Operations and Maintenance, Pneumatic Controls | 2 Comments

Economizers–The Physics of Linkage Systems

In the post before the previous, I was discussing an economizer performance problem in a facility we worked with as a class in Monterey California.  One of the problems was related to the mechanics of motion in the linkage system … Continue reading

Posted in Air Handling Systems, Controls, Economizers, Pneumatic Controls | Leave a comment

Economizers–The Physics of a Mixed Air Plenum

I’ve been working on a post that shows how a scatter plot technique can be used to assess the performance of an HVAC airside economizer.  It’s based on comparing a plot of outdoor air temperature vs. mixed air temperature for … Continue reading

Posted in Air Handling Systems, Controls, Economizers, HVAC Calculations, HVAC Fundamentals, Psychrometrics | Leave a comment

Applied Psychrometrics – the Psych Chart Dry Bulb Temperature Axis (Plus a Bit about Dry Bulb Thermometers)

This post looks at dry-bulb temperature and how it is measured.  Then, it looks at how you plot a dry-bulb temperature on a psych chart.  The links below will jump you to the various topics in the post. What Is … Continue reading

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4-20 ma Current Loop Experiments – Thermal Mass Effects

In this post, I will look at how thermal mass impacts a temperature reading, as can be seen in this video clip where I apply heat to a sensor inside a well while letting you watch a meter displaying the … Continue reading

Posted in 4-20 ma Current Loops, Controls, Data Logging | Leave a comment

4-20 ma Current Loop Experiments – Position Sensitivity

The next few posts will supplement a string of posts I did a while back on 4-20 ma current loops, including a couple of posts that show you how to build a DC power supply panel so you can use … Continue reading

Posted in 4-20 ma Current Loops, Controls | Leave a comment