I was wondering if it is possible to increase the output voltage beyond 3kV with an external power supply or a second 2657A SMU. What I'm thinking about is having a negative polarity DC power supply (1kV) with ground connected to the ground of the 2657A. That way the device sees the variable Vout from the 2657A +1kV. So I could measure a device from 1kV to 4kV with the last 3kV of it as variable based on the 2657A. This would also mean there is no potential to ground (Vcommon) of more than 3kV. To do this though, I would need to know where to connect the ground. I assume the current sensor of the 2657A is inside the box and to accurately measure the current, the ground of the 1kV suppl would need to go through the low side of 2657A to correctly measure current? I understand it will not meausure the full device voltage but I would, in theory, only need to add the fixed voltage of the supply to reading to get the voltage across the device.
Is this something that is do-able? Sounds like it should be possible but I'm not sure. Would it require a floating (chassis/low side not connected to earth ground) DC supply with low side to ground of 2657A?
- Keithley Applications
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If you use a fixed power supply, you can achieve zero volts by driving the 2657A output to the same voltage as the power supply. If your supply is 1kV, you can achieve 0 to 4kV by operating the 2657A from +1kV to -3kV.
You should always use a proper interlock to achieve safety when working with high voltages. The 2657A has a proper interlock designed into the instrument. Your power supply may not have the same level of safety built in. If not, you should design a way to achieve an interlock.
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