The Keithley 2182A Nanovoltmeter is optimized for making stable, low noise voltage measurements and for characterizing low resistance materials and devices reliably and repeatably. It provides higher measurement speed and significantly better noise performance than alternative low voltage measurement solutions.

The 2182A represents the next step forward in Keithley nanovoltmeter technology, replacing the original Model 2182 and offering enhanced capabilities including pulse capability, lower measurement noise, faster current reversals, and a simplified delta mode for making resistance measurements in combination with a reversing current source.

Flexible, Effective Speed/Noise Trade-Offs

The 2182A makes it easy to choose the best speed/filter combination for a particular application's response time and noise level requirements. The ability to select from a wide range of response times allows optimizing speed/noise trade-offs. Low noise levels are assured over a wide range of useful response times, e.g., 15nV p-p noise at 1s and 40-50nV p-p noise at 60ms are typical.

Figure 1. DC Noise Performance

Figure 2. Delta Mode

Figure 3. Connect 2182A to the 6220/6221

Reliable Results

Power line noise can compromise measurement accuracy significantly at the nanovolt level. The 2182A reduces this interference by synchronizing its measurement cycle to line, which minimizes variations due to readings that begin at different phases of the line cycle. The result is exceptionally high immunity to line interference with little or no shielding and filtering required.

An Easy-to-Use Delta Mode

Keithley originally created the delta mode method for measuring voltage and resistance for the Model 2182 and a triggerable external current source. Basically, the delta mode automatically triggers the current source to alternate the signal polarity, and then triggers a nanovoltmeter reading at each polarity. This current reversal technique cancels out any constant thermoelectric offsets, so the results reflect the true value of the voltage being measured. The improved delta mode for the 2182A current sources uses the same basic technique, but the way in which it's implemented has been simplified dramatically. The new technique can cancel thermoelectric offsets that drift over time (not just static offsets), produces results in half the time of the original technique, and allows the current source to control and configure the 2182A. Two key presses are all that's required to set up the measurement. The improved cancellation and higher reading rates reduce measurement noise to as little as 1nV.

Figure 4. Transient Currents

Figure 5. Delta Mode

Differential Conductance Measurements

Characterizing non-linear tunneling devices and low temperature devices often requires measuring differential conductance (the derivative of a device's I-V curve). There's no need to average the results of multiple sweeps, because data can be obtained in a single measurement pass, reducing test time and minimizing the potential for measurement error.

Metrology Applications

The 2182A combines the accuracy of a digital multimeter with low noise at high speeds for high-precision metrology applications. Its low noise, high signal observation time, fast measurement rates, and 2ppm accuracy provide the most cost-effective meter available today for applications such as intercomparison of voltage standards and direct measurements of resistance standards.

Research Applications

The 2182A's 1nV sensitivity, thermoelectric EMF cancellation, direct display of "true" voltage, ability to perform calculations, and high measurement speed makes it ideal for determining the characteristics of materials such as metals, low resistance filled plastics, and high and low temperature superconductors.