Self Calibration ADCC Ratio Bridge AccuBridge®
Since 1994, the 6010 technology has set the standard for DC Current Comparator (DCC) Resistance Bridge performance in calibration laboratories globally. The time has now come to advance this best-in-class series, taking advantage of twenty-first century AccuBridge® ADCCC technology.
Measurements International’s (MI) major technological advantage in resistance measurements is the development of the only commercially available portable Quantum Hall System, QUANTΩ, (Figure 1) which uses a AccuBridge® ADCC technology bridge as the measurement system operated in ambient temperatures. Like all our DCC bridges the current range is from 1 uA to 200 mA for use as a Quantum Hall Bridge and a resistance bridge . The ADCC 6020Q features increased ampere turn sensitivity (more turns) on both the slave and master winding’s and a new voltage feedback circuit to improve on the linearity error of the nano volt amplifier.
MIL has world class expertise in both DC Resistance Metrology at NMI’s and 17025 Accreditation throughout industry. As your accreditation partner and global support partner, MIL offers leading product knowledge and applications expertise through coaching, system design, implementation, calibration services and ongoing expert support insuring your competitive advantage.
It’s not only about the equipment or the science….It’s about what that will enable you to do, and the ease with which you can do it.
The AccuBridge® 6020Q room temperature ADCC Quantum Hall Resistance Bridge can be used to characterise both the GaAs/AlGaAs (Figure 2) or Graphene samples by measuring and plotting the field sweep, the contact resistance (Vcr), the longitudinal resistance and dissipation of the I = 2 plateau (Vxx) and transferring the Hall Resistance (Vxy) to a 1,000 Ω standard resistor.
Enhancements using AccuBridge® ADCC technology include a higher ampere turn sensitivity covering a wider range of resistance ratio, a current and voltage feedback circuit for increased linearity performance and a new calibration technique with increased resolution in obtaining even tighter specifications. In addition to the updated technology, it carry’s the 6010’s dependability, simplified calibration, ease-of-use, automation, speed of measurement and worldwide support making the 6020Q the BEST and ONLY Resistance Bridge that offers uncertainty specifications that rival anything available today.
The AccuBridge® 6020Q is a fully automated bridge. Its speed, precision and measurement accuracy accounts for its preferred status as the primary resistance bridge in most NMIs throughout the world. It is designed for flexibility and ease of use and is perfectly suited for stand-alone resistor calibrations.
The Accubridge® 6020Q has two inputs, Rx and Rs. The number of inputs can be expanded to 40 when used in conjunction with the 4200 Series Low Thermal Four Terminal Matrix Scanners (Figure 3). Measurements can be performed automatically and with Measurements International’s 6020Q software delayed or scheduled measurements can all be performed at any time. Automatic current reversal ensures that dc offsets and thermals in the bridge and scanner are canceled out during the measurement. See the 4200 Data Sheet for a complete range of Matrix Scanners.
As a stand-alone device, the 6020Q is capable of performing the sweep check, contact resistance, the longitudinal potential difference (dissipation) and Hall resistance measurements on the QHR sample (Fig 2). Menu driven functions are selectable using the front panel display or over the GPIB488. In addition, the 6020Q dcCCC current comparator bridge can be used as a high accuracy dc resistance ratio bridge in its own right for calibrating resistors using either a 1Ω or 10KΩ standard resistor. For laboratories that don`t have a QHR system, the 6020Q can be used to build up from the 1Ω or down from the 10kΩ.
Sweep Check Measurement: The 6020Q performs the field sweep check measurement by feeding a current into the Source & Drain of the sample and then reversing it. This allows the measurement of potential differences between various points on the sample. These potential differences can be measured at Hall resistances Vxy(1-2) or Vxy(3-4) and the longitudinal resistance Vxx(1-3) and Vxx(2-4) on the sample. Vxy(1-2) and Vxy(3-4) should be in close agreement with each other as should Vxx(1-3) an Vxx (2-4).
Contact Resistance Measurements are made using the microvolt detector in the 6020Q. It is important to measure the contact resistance each time the QHR device is cycled to room temperature and re-cooled as large contact resistances can lead to errors in the QHR measurement. The 6020Q uses a three probe measurement on each of the contacts in turn to measure the contact resistance. The contact resistance is equal to V(cr)/I = resistance of wire + resistance of contact + resistance of 2-Deg. The contact resistance should be ideally less then 1Ω.
Dissipation: For an accurate transfer of the QHR value it is also necessary to measure the longitudinal potential difference. This can be accomplished by measuring between Vxx(1-3), and Vxx(2-4) using the 6020Q Vxx nanovolt mode. This measurement is taken to verify that there is no dissipation in the 2-Deg. When the 2-Deg is quantized Vxx should go to 0 and should be < 2 x 10-8 of Vxy.
For traceable measurements, the QHR value and related uncertainty are entered in the resistor ID standards file and the 1,000Ω transfer resistor into the measurand (unknown) ID file from the keypad. Standard Resistors such as the 1Ω or 10kΩ are entered into the standards file after they have been calibrated. Resistors to be Figure 5 calibrated are entered into the measurand (Rx) or unknown file. Measurement
functions such as current through the unknown resistor, settle time, a number of measurements and number of statistics are also entered into the Programs file using the keypad on the touch screen.
Please see data sheet for specification table