(I have an understanding of component level electronics but not mains installations regulations)
I have a machine at work that is supplied by 240vac, L,N & E. The machine is also separately bonded to earth.
If I run a wire directly to the building earth point to use as a reference, I can measure (using a standard multimeter) a resistance of 120ohm between the machine earth wire & my reference wire(supply earth, not bonding earth).
If I remove the earth wire from the machine and test it I get a good reading of less that 1 ohm to my reference wire.
I can't understand that this 1ohm wire goes up to 120ohm just from connecting it to "another" good earth. I thought resistors in parallel made the total resistance go down , not up ?
Help!
I have a machine at work that is supplied by 240vac, L,N & E. The machine is also separately bonded to earth.
If I run a wire directly to the building earth point to use as a reference, I can measure (using a standard multimeter) a resistance of 120ohm between the machine earth wire & my reference wire(supply earth, not bonding earth).
If I remove the earth wire from the machine and test it I get a good reading of less that 1 ohm to my reference wire.
I can't understand that this 1ohm wire goes up to 120ohm just from connecting it to "another" good earth. I thought resistors in parallel made the total resistance go down , not up ?
Help!