Measurements International - Metrology is our Science, Accuracy is our Business

Since 1992, the Measurements International’s (MI) 6010 series has set the standard for research, calibration and measurement of resistors and shunts in both NMIs and calibration laboratories around the world. Now the time has come to advance this best-in-class, the MI 6010 series of DC Resistance and Temperature Bridges, taking advantage of AccuBridge^® technology and usability. In particular, the MI 6010D High-Performance Resistance Bridge is the culmination of years of engineering development, customer research and industrial design, to bring to market the new standard in resistance, shunt and DCCT research, measurement and calibration. Measurements International’s (MI) series of DCCT Measurement Systems offers the best accuracy and lowest uncertainty of any commercial system available on the market today. The MI High Current Range Extenders expand the measuring capabilities of the MI model 6010 and MI model 6242 to measure lower resistance values at higher currents with accredited uncertainties < 20 ppm @ 10 µΩ to 0.1 ppm @ 1 Ω and 0.1 ppm @ 10 kΩ being achievable.

High Performance with Increased Applications

The 6010 can be used to calibrate a wide range of resistance standards (0.1 Ω to 100 kΩ) and with the addition of the MI series of range extenders and power supplies the calibration of high current shunts (1 µΩ to 100 mΩ).

In industrial current measurements, the best measurement uncertainties in DC current measurements are reached using DC current transformers (DCCTs). DCCTs have the advantage that there is no warm-up period but are more capacitive and inductive than current shunts and so the reversal rate is fairly long to achieve the best accuracy. Several commercial DCCT devices are available on the market now with accuracies approaching 10^-5. For the application of research and calibration of the DCCT, MIL is pleased to announce the model 6300 series of DCCT calibration systems where measurement uncertainties of less than a few ppm for DC currents from 1 A to 3 kA can be achieved.

The new MIL setup is based on proprietary high-current DC Range Extenders from MI with ratios up to 1:1,000,000. Two measurement techniques can be used to measure the transimpedance of a DCCT. The MI model 6010D (Resistance Bridge) or the MI model 6300A which uses two 8½ digit DMMs (3458A) as measuring devices. The 6010D is developed around the well-established AccuBridge^® technology, the transimpedance is obtained by accurately measuring the current ratio using the bridge. This 6010D system provides the best accuracy for the voltage output DCCTs. The 6300A is based on two 8½ digit DMMs (3458A). With this system, the absolute value of the test current is required, which is limited by the DMM accuracy. The model 6300A will measure both voltage and current output DCCTs.

Figure 1 shows a picture of a simple setup using the Model 6300A/100 which includes a model 6011D Range Extender, a standard resistor, two DMM’s and a 4210A Scanner for calibrating multiple DCCTs at the same time. This system can also be used for the calibration at currents up to 300 A by winding 3 turns of the primary current lead through the center hole of the DCCT under test extending the range of the 6011D. The uncertainty achieved in this particular calibration is < 0.5 ppm, limited by the behaviour of the DCCT. In practice, the limit will be set by the amount of turns N that physically fit through the center hole of the DCCT. The uncertainty achieved in this particular calibration is < 1 ppm, limited by the behaviour of the DCCT.

<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>