What is 4-20 ma?

This article will be geared towards the curious, I am not going to try to train you how to work with the subject materiel.
But you will be able to converse intelligently after reading this.

BASIC DEFINITION

4-20ma can be either an input or output from the perspective of a PLC, (Programmable Logic Controller)which was covered in an earlier article.
The PLC specialty cards necessary are referred to as Analog cards(both input and output types).

MA stands for milliamp, a measurement of current flow. 4-20 is the lower and upper limits of this defined scale.
One example is the use of this scale to order a motor to run at a specific speed, with 4ma representing stopped and 20ma representing full speed.

Continue reading “What is 4-20 ma?”

A little about PLC’s

It seems to me that most information available on this topic assumes a moderate knowledge level before beginning their discussion, so I intend to break this down a little to accommodate those of you who may not have even heard of PLC’s before today.  Along the way, I will share my perspective as someone who has been working “hands-on” since the late eighties.
The most basic form of PLC’s are hardened, industrialized PC’s which provide inputs and outputs. Continue reading “A little about PLC’s”

About Motor troubleshooting and the use of Meggers…

This particular activity is potentially very dangerous because power needs to be applied and locked out frequently, so please follow proper lockout-tagout procedures!
Meggers are a must in the area of industrial electrical troubleshooting because they can help quickly identify some sources of malfunctions while eliminating other sources as the cause of the malfunction.
As an example, let’s say that a motor refuses to turn. The problem could be coming from let’s say 3 different directions. Continue reading “About Motor troubleshooting and the use of Meggers…”