That's the problem. Put a resistor in series with the switches common and recalculate U2C feedback resistor or subtract the resistor's value from each of the 2.7k, 7.5k and 9.1k resistors connected to the switch. I tried it with 1k and it works.the common of S1 to the inverting input of U2C.....
You could use an IC like the LT1054. it creates a negative voltage from a positive voltage. Came to my mind because I had it at hand, there are other ICs doing the same thing. You will need the IC plus 2 additional capacitors and you'll have about -9V from +9V input. Adds cost too, though.Yea, actually earlier today i increased it to 15V and i got the +/-5V at the output..just had to change some resistor values. The thing is that the 15V adds cost to the circuit as i will need a power supply addition.
I think what Sgt meant by "earth ground" is the buildings ground.Physically speaking, if i am using the power supply to test the circuit (instead of the 9V battery) what do you mean by isolating it from earth ground. All my earth grounds are connected to the -ve power supply.
YesSo if the power supply is not referenced to the buildings ground and the scope is connected to the buildings earth ground then...connecting the -ve of the power supply to the minus of my circuit and connecting the scope GND to the virtual ground should be right not so?
The low voltage workbench power supply outputs I work/worked with are all isolated from buildings earth connection. They have however a ground connection at the front, which I normally don't use. It wouldn't be very clever to have a laboratory DC power supply where it's "-" output is connected to buildings ground. If you post your power supply model, I'm sure we can tell you.If the power supply is referenced to the buildings ground however, how can it be isolated??
Or how can i knw whether the scope is isolated or not?
The part i dont get is how a scope or power supply can be isolated.
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