The Keithley 6221/2182A Complete Delta Mode System w/AC/DC Current Source Meter/Nanovoltmeter combines ease-of-use with exceptionally low-current noise. Low-current sourcing is critical to applications in test environments ranging from R&D to production, especially in the semiconductor, nanotechnology, and superconductor industries. High sourcing accuracy and built-in control functions make the 6221/2182A ideal for applications like hall measurements, resistance measurements using delta mode, pulsed measurements, and differential conductance measurements. Combining the 6221 with a 2182A Nanovoltmeter makes it possible to address both of these challenges.

The Need for Precision, Low-Current Sourcing

Device testing and characterization for today's very small and power-efficient electronics requires sourcing low-current levels, which demands the use of a precision, low-current source. Lower stimulus currents produce lower - and harder to measure - voltages across the device.

Simple Programming

Both current sources are fully programmable via the front panel controls, or from an external controller via RS-232 or GPIB interfaces. The 6221/2182A can source DC currents from 100fA to 105mA. The output voltage can be set from 0.1V to 105V in 10mV steps. Voltage compliance (which limits the amount of voltage applied when sourcing a current) is critical for applications in which overvoltages could damage the device under test (DUT).

Define and Execute Current Ramps Easily

The 6221/2182A offers tools for defining current ramps and stepping through predefined sequences of up to 65,536 output values using a trigger or a timer; it supports linear, logarithmic, and custom sweeps.

Free Instrument Control Example Start-up Software

The instrument control example software available for the sources simplifies both performing basic sourcing tasks and coordinating complex measurement functions with the 2182A. The software, developed in the LabVIEW programming environment, includes a step-by-step measurement guide that helps users set up their instruments and make proper connections, as well as program basic sourcing functions. The advanced tools in the package support delta mode, differential conductance, and pulse mode measurements. From this package, users can print out the instrument commands for any of the pre-programmed functions, which provides a starting point for incorporating these functions into customized applications.

Differential Conductance

Differential conductance measurements are among the most important and critical measurements made on non-linear tunneling devices and on low temperature devices. Mathematically, differential conductance is the derivative of a device's I-V curve. The 6221, combined with the Model 2182A Nanovoltmeter, is the industry's most complete solution for differential conductance measurements. Together, these instruments are also the fastest solution available, providing 10× the speed and significantly lower noise than other options. Data can be obtained in a single measurement pass, rather than by averaging the result of multiple sweeps, which is both time-consuming and prone to error. The 6221/2182A is also easy to use because the combination can be treated as a single instrument. Their simple connections eliminate the isolation and noise current problems that plague other solutions.

Delta Mode

Keithley originally developed the delta mode method for making low noise measurements of voltages and resistances. Essentially, delta mode automatically triggers the current source to alternate the signal polarity, then triggers a nanovoltmeter reading at each polarity. This current reversal technique cancels out any constant thermoelectric offsets, ensuring the results reflect the true value of the voltage.

This same basic technique has been incorporated into the Model 6221/2182A delta mode, but its implementation has been dramatically enhanced and simplified. The technique can now cancel thermoelectric offsets that drift over time, produce results in half the time of the previous technique, and allow the source to control and configure the nanovoltmeter, so setting up the measurement takes just two key presses. The improved cancellation and higher reading rate reduces measurement noise to as little as 1nV.

Delta mode enables measuring low voltages and resistances accurately. Once the 6221 and 2182A are connected properly, the user simply presses the current source's Delta button, followed by the Trigger button, which starts the test. These devices work together seamlessly and can be controlled via its GPIB, or Ethernet interfaces.

Pulsed Tests

Even small amounts of heat introduced by the measurement process itself can raise the DUT's temperature, skewing test results or even destroying the device.