Most of us know that a good grounding system is important. However, not all of us understand why, and even fewer really understand how to make sure it’s working as planned. Luckily, there are those in the know who share this valuable information with the rest of us.
Once such resource was put together recently by Fluke® in a report titled “Don’t forget the grounding system – Prevent equipment failure and stay safe.” You can read the full report and learn how to test your grounding system here.
As is typical, however, we’ll give you a synopsis and discuss how it applies to level and pressure transducers.
Not only do you need little resistance to earth, you need equal resistance between grounding points. If you have more than one ground, and the resistance is not equal, then you’ll get a ground loop. A ground loop will cause problems with electrical noise.
If you’re using a submersible pressure transducer, a ground loop can also result in electrolysis.
To prevent a ground loop, you’ll need to carefully test the resistance at each ground point. Fluke’s report details several testing methods that are all possible with their suite of tools.
Resistance Changes Over Time
Testing is also important over time because resistance changes over time. As Fluke states in their report, “corrosive soils with high moisture content, high salt content, and high temperatures can degrade ground rods and their connections.”
This will result in an increase of resistance to ground over time. As your ground becomes less reliable, the risk of electrical noise, damage to equipment, and personal injury increase.
Having an annual testing procedure is important to ensure that your instruments perform as expected and your employees stay safe.
How Much Resistance Is Good
There is some confusion out there about what a good resistance value is for a ground point. Of course, the ideal resistance would be zero ohms. However, there is no global standard.
However, several standards do recommend – especially for sensitive equipment – a value of 5 ohms or less.
“The goal in ground resistance is to achieve the lowest ground resistance value that makes sense economically and physically.”
Let us know if you have any questions about grounding your APG sensors, or their electrical requirements. Our application techs are happy to help you sort through any installation or support issue you might be facing.
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