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Calculating "Charge" Through Device

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Joined: February 18th, 2016, 3:09 am
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Calculating "Charge" Through Device

Post by TCDPapu » February 18th, 2016, 3:18 am


I was hoping someone could help me in clarifying details on the source-delay-measurement cycle.
I am trying to calculate the total charge which has flown through my device, my first approach was the multiply the current value by the time step, but I am not sure that this is correct.

Say I was to perform a dual linear voltage sourced measurement 0-1V with .1v step. With a .1s time delay.

with timestamp enabled I have a series of time values, what do these time values represent? the start of the measurement cycle? or where the sourcing has begun? between each of the timestamp values has the potential across my device increased by .1v?

also if my device reaches current complience the SMU becomes a current source, how can i know the length of time that the constant current is being applied to my system?

Is there a better way to do this measurement?

Many thanks,

Keithley Applications
Keithley Applications
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Joined: June 10th, 2013, 6:00 am
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Re: Calculating "Charge" Through Device

Post by brian.d.smith » February 27th, 2016, 6:35 am

Our electrometers can measure charge as one of the fundamental features. That said, the principal of charge, Q, is

Q = C * V and dQ/dt = C dV/dt
dQ/dt is current, so

I = C * dV/dt

The change in charge from sweep point to sweep point, dQ, will be C * dV

Knowing I and V is not enough. You need to know the capacitance, C, of your device.

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