The Keithley 6487 Picoammeter/Voltage Source's 10fA resolution, superior sensitivity, voltage sweeping, and Alternating Voltage resistance measurements make it well suited for characterizing low current devices. Using the latest current measurement technology, it is significantly less expensive than other instruments that perform similar functions, such as optical power meters, tera-ohmmeters, competitive picoammeters, or user-designed solutions. With a price that's comparable to a high-end DMM, the 6487 makes picoamp-level measurements affordable for virtually any laboratory or production floor.

Low Voltage Burden and Higher Accuracy

While DMMs typically employ shunt ammeter circuitry to measure current, the 6487 is a feedback picoammeter. This design reduces voltage burden by several orders of magnitude, resulting in a voltage burden of less than 200μV on the lower measurement ranges. The low voltage burden makes the 6487 function much more like an ideal ammeter than a DMM, so it can make current measurements with high accuracy, even in circuits with very low source voltages.

Rear Panel Triax Input

This allows the picoammeter to be used in floating operation, up to 500V. When not floating, the addition of a triax to BNC adapter allows inexpensive, easy-to-use BNC cables to be employed, rather than more expensive triaxial cables.

RS-232 and IEEE-488 Interfaces

These interfaces make it easy to integrate the 6487 into automated test and measurement systems.

Scaled Voltage Analog Output

This output allows the 6487 to transmit measurement results to devices like DMMs, data acquisition cards, oscilloscopes, or strip chart recorders.

Built-In Trigger Link Interface

The Trigger Link interface simplifies synchronizing the 6487 with other instruments and voltage sources. This interface combines six independent selectable trigger lines on a single connector for simple, direct control over all instruments in a system.

Display On/Off Switch

For research on light-sensitive components, such as measuring the dark currents of photodiodes or I-V measurements on unpackaged semiconductors, the front panel display can be switched off to avoid introducing light that could significantly reduce the accuracy of the results.

One-Touch Front Panel Design

Functions can be configured easily with the push of a button, without complicated function menus.

Wafer-Level Photodiode Testing

The 6487 Picoammeter/Voltage Source can be paired with a calibrated light source and a probing fixture to create a cost-effective photodiode test system. Multiple 6487s can be connected to the DUT's probe pads to provide photocurrent readings or, with the addition of a switch matrix, one picoammeter can take current measurements from multiple pads. In the first step of the measurement process, performed in total darkness, the 6487 produces a voltage sweep and then measures the resulting dark current. In the second step, a voltage bias is applied and the resulting photocurrent is measured while the light level is increased in calibrated steps. The same basic test configuration can be used for testing positive intrinsic negative (PIN) and avalanche photodiodes (APDs). The 6487's high resolution on the 10V source range provides superior sweeping and biasing when small biases are required. The 500V source capability is necessary to bias APDs.

Monitoring and Control of Focused Ion Beam Currents

In semiconductor fabrication, focused ion beam systems are often used for nanometer-scale imaging, micromachining, and mapping. Careful monitoring of the magnitude of the beam current with an ion detector is critical. The ion detector generates a secondary current that's proportional to the current of the primary ion beam. When this secondary current is measured, it can be used to control the intensity of the primary beam. However, this secondary current is very low, often just a few picoamps, so the instrumentation measuring it must provide high measurement accuracy and repeatability, as well as sub-picoamp resolution. The 6487's wide measurement range and 5 1/2-digit resolution make it ideal for this application. Signal connections to the 6487 are made through the instrument's triax connector. Often, a detector may require high voltage to attract ions, making the 6487's 500V source a necessity.

High Resistance Measurements

The 6487 Picoammeter can be used to measure high resistances (>1GW) in applications such as insulation resistance testing. A constant voltage is placed in series with the unknown resistance and the picoammeter. The voltage drop across the picoammeter is negligible, so all the voltage appears across the unknown resistance. The resulting current is measured by the picoammeter and the resistance is calculated using Ohm's Law (R = V/I). To prevent generated current due to electrostatic interference, the unknown resistance is housed in a shielded test fixture. A small series resistor may be added to reduce noise if the unknown resistor has high stray capacitance across it.