40v offset to ground?

No its not normal. The chassis with the screw and marked with the ground symbol is where you are supposed to connect earth ground. You could be getting stray readings because of the high impedance of your meter or something could be wrong. If it were me I would hook the ground to the chassis and see. Regards, Tom

Hi, Scott. First, FG is usually interpreted to mean Field Ground. It's there for safety -- to ensure that, if something goes wrong, a fuse will blow instead of putting the chassis at line potential. Safety first -- use it.

Your floating power supply will have a small leakage current between the line and the chassis, and also between the line and output. That's primarily capacitive, and is nothing to worry about for most applications. One exception is medical, where tenths of a mA of leakage current are critical, for instance with EKG readings -- you can get medical-rated power supplies where this problem is greatly reduced. The thing is, a DVM can have up to 10 megohms of impedance, so it's possibly too good at picking this up.

Try placing a 47K resistor between the cage and GND, and then measure it with your DVM. I'll bet the voltage reading goes way down. If not, your power supply is defective.

Good luck Chris

I'm using a crappy, old analog meter, and I doubt the impedance is megaohms. I'll try the 47k resistor and retest.

I have two of these supplies, a -12s and a -05s. They both report this

40v difference, so if it's a bug, it's an infestation. Anyone know if Kaga supplies are prone to this kind of thing?

I'm still not clear on the difference between an FG and a Gnd, but if it's ok to tie the outlet's ground to FG, I'm happy to do that. There's no actual screw in the screw hole marked Gnd, but there is one in the FG position.

While not always correct, I have found that if you have the old 20,000 ohm/volt meter or similar that if you change the range to another scale and the meter pointer (not the voltage) stayes in about the same position then the meter is picking up some high impedance leakage.

Sometimes a piece of equipment will have the signal ground isolated from the actual chassie (frame) . That gives you two grounds. It is similar to the way the power company and your house is wired. You have a neutral wire going from the braker box and also a ground wire. They are seperate as far as the power transmission goes, but are connected at one point back at the braker box.

Hi, Scott. Real men use analog meters. ;-)

Most all switches are made to have the cage connected to GND. You need to find the actual current, and to do that, you'll need a realistic value resistor. A 47K 1/4 watt resistor is about the smallest value that can handle line voltage for a few seconds (.3W), so I'll typically use one of those. Use your meter to read the voltage across the resistor, and you'll have current. You shouldn't be reading more than a couple of volts.

Power supplies are supposed to be tested for hipot, so this shouldn't be a problem unless the power supply is defective. Do the test, and if it's OK, connect the line cord GND to the chassis (cage) of the switcher, like the manufacturer recommends.

Good luck Chris

I consider "FG" to mean "Frame Ground" - it is a terminal used to connect the frame of the device to ground.

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Peter Bennett VE7CEI 
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I understand FG to mean 'frame ground' as in chassis i.e. the metalwork. Connecting this to the supply ground wire should not affect anything most likely.

Graham