Keithley 2182A

The model 2182A nanovoltmeter is optimized for making low noise measurements in research, metrology, nanotechnology, superconductivity, and other low voltage/resistance applications.

The Model 2182A brings a powerful new set of capabilities to researchers when used in conjunction with Keithley's recently introduced model 6221 AC/DC current source; users now are able to make resistance measurements, pulsed I-V measurements, and differential conductance measurements faster and more accurately than previously possible, in many cases eliminating the need for an expensive lock-in amplifier or AC resistance bridge. The combination is also useful in many nanotechnology applications because of its ability to measure resistance while dissipating very little power in the device under test (DUT).

The Model 2182A is able to minimize DC drift and noise common to low voltage measurements with rapid measurement speeds beyond what is achievable by previous nanovoltmeters or sensitive DMMs. The instrument is able to make 15nV peak-to-peak measurements at one-second response times and 40-50 nV p-p measurements at 60 millisecond times.

The unit features a built-in Delta Mode to coordinate measurements with a reversing current source (one-button operation when used with Keithley model 6221) at up to 24Hz with 3nVrms/root-Hz noise, creating a system optimized for precision measurements of low resistance materials or devices. The new delta mode operation alternates nearly three times faster than its predecessor model, reducing measurement noise by nearly a factor of two. In addition, the new delta mode incorporates a new cancellation method that reduces the effects due to changing thermoelectric voltages by a factor of ten compared to its predecessor.

By synchronizing to line frequency, the Model 2182A provides 110dB rejection to noise at line frequency and minimizes the effect of AC common-mode currents. The unit offers two channels for measuring voltage or temperature. Or, the second channel can be used for reading the ratio of an unknown resistance directly to a reference resistor. Built-in thermocouple calculations for types J, K, N, T, E, R, S, and B are provided.

Integrating the Model 2182A with Keithley’s new current source, model 6221, creates a powerful test system capable of acting as a single instrument. When linked with the Ethernet-enabled Model 6221, the combined system effectively operates as an Internet-controlled nanovoltmeter system, allowing customers to control both sourcing and measuring through a single Internet IP address.

Some of the most important capabilities of the Model 2182A, when combined with the model 6221, include:

* Wide measurement range, from 10 nano-ohms (lowest noise) to 1 Gohms.

* Differential conductance, an increasingly common measurement for characterizing semiconductor and nanotechnology materials, can be performed 10X faster and with lower noise by the Models 6221 and 2182A than by existing solutions, including lock-in amplifiers and AC resistance bridges.

* When combined with the Model 6221, the Model 2182A can support pulsed resistance and pulsed I-V measurements with pulses as short as 50 microseconds, even at low currents. Short pulses mean less power put into the DUT, particularly important in very small devices where even a small amount of power may be enough to destroy the device or produce an invalid reading. To eliminate DC offsets and line frequency noise in these sensitive pulse measurements, the 6221/2182A pulsed mode utilizes both line synchronization and delta-mode techniques.

Key Features and Benefits:

• Make low noise measurements at high speeds, typically just 15nV p-p noise at 1s response time, 40-50nV p-p noise at 60ms
• Delta mode coordinates measurements with a reversing current source at up to 24Hz with 30nV p-p noise (typical) for one reading. Averages multiple readings for greater noise reduction
• Synchronization to line provides 110dB NMRR and minimizes the effect of AC common-mode currents
• Dual channels support measuring voltage, temperature, or the ratio of an unknown resistance to a reference resistor
• Built-in thermocouple linearisation and cold junction compensation

The two-channel Model 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.

Related Applications:

• Research
• - Determining the transition temperature of superconductive materials
• - I-V characterisation of a material at a specific temperature
• - Calorimetry
• - Metrology
• - Intercomparisons of standard cells
• - Null meter for resistance bridge measurements