Electronic Design

Picoammeter Merges 500-V Source With 20-fA Current Sensitivity

Providing an unusual set of measurement capabilities, the Model 6487 picoammeter/voltage source combines low current sensitivity near that of an electrometer with the ease of use of a high-performance digital multimeter (DMM). The 5-1/2-digit instrument can apply a voltage stimulus as high as 500 V to a device under test and measure currents as low as 20 fA. It provides direct readout of resistance measurements up to 5.0 * 1016 ‡ using the source-voltage, measure-current method. An alternating voltage method that minimizes background current errors is also included. The unit has a data-acquisition rate of 1000 readings/s into buffer memory. The instrument's 20-fA sensitivity allows it to characterize low-current phenomena while its 20-mA range lets it measure current high enough for 4- to 20-mA sensor loops. Accurate measurements are achieved with the the instrument's high resolution and low voltage burden of less than 200 µV on lower measurement ranges. The Model 6487 can take overloads up to 505 V dc (maximum commode-mode and continuous input). The voltage source ranges are ±10, ±50, and ±500 V dc, with a basic accuracy of ±0.1% on the programmed value. Thanks to a scaled voltage analog output, the instrument can transmit measurement results to devices like DMMs, data-acquisition cards, and oscilloscopes. The Model 6487 costs $2995.

Keithley Instruments Inc. www.keithley.com; (888) 534-8453

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