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The Keithley 238 Source-Measure Unit (SMU) is a fully programmable instrument, capable of sourcing and measuring voltage or current simultaneously. It is really four instruments in one: voltage source, current source, voltage measure and current measure. The Keithley 238 offers a decade enhancement in current source and measure (IA). In this higher current range, voltage source and measure is 15 V maximum. It will measure very small currents and voltages. With current sensitivity of 10 fA, measurement capabilities are equal to those of an electrometer. Selectable integration and the filtering of multiple measurements enhances sensitivity for demanding applications. Both source voltages and source currents settle to specified accuracy in as little as 500 µs. Programmable delay and fast, integrating measurement capability can provide coordinated source-measure times of 1 ms. Specifications. Voltage Source range: ±1.5000 V (step 100 µV), ±15.000 V (step 1 mV), ±110.00 V (step 10 mV). Voltage Measure range: ±1.5000 V (resolution 10 µV), ±15.000 V (resolution 100 µV), ±110.00 V (resolution 1 mV). Current Source minimum range: ±1.0000 nA (step 100 fA). Current Source maximum range: ±1.0000 A (step 100 µA). Current Measure minimum range: ±1.0000 nA (resolution 10 fA). Current Measure maximum range: ±1.0000 A (resolution 10 µA). Wideband Noise: 0.1 to 20M Hz, 8 mV p-p typical. Overshoot: <0.01 % (100 V step, 10 mA range). Settling Time: <500 µs to 0.01 % (110 V step, 10 mA range). Remote Sense: Corrects for up to 2V drop in each output lead. Maximum 1 k-ohm per sense lead for rated accuracy. Residual output resistance (as a voltage source) is 0.5 ohm.
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