6300A DCCT Calibration System

Since 1992, the Measurements International (MI) 6010 series has set the standard for research, calibration and measurement of resistors and shunts in NMIs and calibration laboratories worldwide. Today, that best-in-class series moves forward. The MI 6010 series of DC Resistance and Temperature Bridges now incorporates AccuBridge® technology and a more intuitive user experience. The flagship MI 6010D High-Performance Resistance Bridge is the result of years of engineering development, customer research and industrial design, and it sets a new standard for resistance, shunt and DCCT research, measurement and calibration.

MI’s DCCT measurement systems offer the best accuracy and lowest uncertainty of any commercial system available today. MI High Current Range Extenders expand the capabilities of the MI model 6010 and model 6242, allowing lower resistance values to be measured at higher currents. Accredited uncertainties of < 20 ppm at 10 µΩ, 0.1 ppm at 1 Ω and 0.1 ppm at 10 kΩ are achievable.

High Performance with Increased Applications

The 6010 calibrates a wide range of resistance standards (0.1 Ω to 100 kΩ). With MI range extenders and power supplies added, it can also calibrate high-current shunts (1 µΩ to 100 mΩ).

For industrial DC current measurement, DC current transformers (DCCTs) deliver the lowest uncertainties. They need no warm-up period. However, they are more capacitive and inductive than current shunts, so a longer reversal time is needed to reach the best accuracy. Several commercial DCCTs now approach accuracies of 10⁻⁵. To support DCCT research and calibration, MI is pleased to introduce the Model 6300 series of DCCT calibration systems, which achieve measurement uncertainties of a few ppm or less for DC currents from 1 A to 3 kA.

The 6300 series is built on MI’s proprietary high-current DC Range Extenders, with ratios up to 1:1,000,000. It offers two ways to measure the transimpedance of a DCCT:

• Model 6010D Resistance Bridge: Built on well-established AccuBridge® technology, it determines transimpedance by accurately measuring the current ratio. This gives the best accuracy for voltage-output DCCTs.
• Model 6300A: It uses two 8½-digit DMMs (3458A). This approach requires the absolute value of the test current, so accuracy is limited by the DMMs. The 6300A can measure both voltage-output and current-output DCCTs.

Figure 1 shows a simple setup using the Model 6300A/100. It includes a Model 6011D Range Extender, a standard resistor, two DMMs and a 4210A Scanner, which allows several DCCTs to be calibrated at the same time. The system can also calibrate at currents up to 300 A. To do this, wind three turns of the primary current lead through the center hole of the DCCT under test, which extends the range of the 6011D. The uncertainty achieved is < 0.5 ppm, limited by the behaviour of the DCCT. In practice, the upper limit is set by the number of turns (N) that physically fit through the center hole.

<sup>1. 2 sigma ratio accuracy of the 6010D is 0.04 ppm.
2. Current accuracy is < 0.01 % = 0.01 ppm in ratio.
3. 3458A accuracy without Acal and with Acal. (Accuracy depends on how well the 3458A can be calibrated.)</sup>