Keep shop voltage under control.

Dear Editor,

C & E shops need to make sure the source of DC voltage in their shop is correctly grounded. Many of them aren't.

If you're working on commo equipment and have noticed sparks between your work bench or other grounded objects or have been "bitten" by electricity, you need to check the ground on the central station power supply that provides 28 DC volts.

Many of these supplies are capable of producing 200 or more amperes of current. That's enough to cause serious injury!

Almost all these power supplies have two output terminals--positive and negative. Neither of these terminals are connected to the power supply's chassis!

Here's what you, need to do: Connect the negative terminal of the power supply to the station ground buss with a cable of sufficient size to handle the entire output capacity of the power supply.

Now check the voltage between the positive terminal to the ground. If you get 28 DC volts, you're okay.

Don't be fooled by a "no voltage reading" on your meter when you check for voltage between the ground and the negative side of the power source. Verify the connection both visually and with a continuity check with an ohm meter.

Edward Butorajac

Ft Gordon, GA

From the desk of the Editor

Shop power supplies are often installed by folks who are not aware of the need to have the chassis and the negative terminal of the voltage source bonded together and connected to the station ground for proper grounding. This could lead to a shock hazard, arcing of the chassis to the work bench or other grounded item, or RF burns. Take Ed's advice and check out your shop's power supply for the right grounds. Also, check the power supply TM or manufacturer to make sure that the power supply is installed properly and that tying the secondary to ground is okay.