I heard some dialogue on this topic in our facility just lately, and thought it could make a very good weblog article.
The protection our bodies (UL, CSA, IEC and so forth.) require and digital merchandise are suitably protected and examined; to make sure the person doesn't get shock that would injure and even kill.
One of many areas of concern is the grounding (earth) of the product, and the next assessments are performed; not simply throughout product security certification testing, but additionally in manufacturing. That is mandated on all merchandise with a pluggable power wire.
The bottom continuity take a look at verifies the connection between the bottom pin on the power wire and any uncovered metallic components on the tools. An AC or DC voltage can be utilized, and the present is usually fairly low, lower than 1A. A easy handheld device can be utilized for testing
Not like the continuity take a look at, the bonding checks the integrityof the grounding. That is sometimes measured utilizing a 25 or 30A present (relying upon the ranking of product’s internal AC fuse or department circuit) simulating an precise internal fault. The utilized voltage is lower than 12V and the utmost resistance between the earth and uncovered metallic surfaces is 0.1 ohm. The resistance may be decided by measuring the voltage drop. Relying upon the security company necessities, this take a look at is carried out for 60 to 120 seconds.
Utilizing the next present than the continuity take a look at ensures that any within the floor path is absolutely tightened, any wire joints are correctly crimped, and any printed wiring board traces are actually able to dealing with the present. The fuse or breaker ought to open earlier than a lack of the bottom connection.
There are a selection of commercially obtainable testers on the market than may be programmed for manufacturing use.
In the event you design your individual tester there are two issues it is best to note:
- Just be sure you don't embody the cable drops when measuring the voltage (have the meter learn on the connection factors)
- Apply the take a look at probes when there is no such thing as a power utilized; in any other case the ensuing spark can mark the metallic components and injury the plating.
As a note floor bonding could also be even be known as earth bonding.