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Low Noise, High Resistance Measurement

Models 2400, 2401, 2410, 2420, 2425, 2430, 2440, 6430
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dnagasawa
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Joined: January 24th, 2011, 10:59 am
Country: United States

Low Noise, High Resistance Measurement

Post by dnagasawa » January 24th, 2011, 11:10 am

Hi.

I need the Keithley 2400 to take high resistance, low noise I-V curves. Expected resistances are about 10-100 Gigaohms and due to the nature of the device being measured (in a cryogenic system), we cannot use more than +/- 5V in our measurements in order to minimize heating of the system. We've tried doing this with stock settings and failed because the sourcemeter's voltage was still overheating our system (even at low voltages). We did not experience this problem earlier using a separate DC power supply and a -.

So is there a way to achieve these high resistance, low noise I-V curves using this device?

Thanks in advance for the help.

Dale C
Keithley Applications
Keithley Applications
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Re: Low Noise, High Resistance Measurement

Post by Dale C » January 24th, 2011, 12:56 pm

The Model 2400 is on the edge of being able to do this measurement accurately.
Consider that 5V into 100G ohms develops only about 50pA.
The current measurement sensitivity of the Model 2400 is 10pA with about 300pA of uncertainty.
I am surprised that the 2400 is over heating your device. Since this is such a low current developed, I would not expect this to be a problem.
For this measurement I would recommend the Model 2635A. This unit is an SMU but is much more sensitive, around (1e-15A).
The voltage source could be much lower because the Model 2635A can measure much lower current.
But I am still puzzled why the 5V of the 2400 would cause over heating.
You could set the compliance on the 2400 to very small (e.g.1nA?) maybe that would help.

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