MEASUREMENTS INTERNATIONAL BRIDGE - Model 5581

Several companies manufacture high-quality resistance bridges for both AC and DC applications. All of these bridges can take measurements at the 0.1 ppm level, and research has shown that all of them compensate well for any theoretical inaccuracies predicted in their design.

We like the MI bridge because we feel confident about our measurements, and its software gives us more information than we can get from the other instruments. While it’s true we do use the other bridges for certain functions we undertake in our lab, including some experimental testing, the MI bridge is used every day for fixed-point calibrations of SPRTs. It’s extremely quiet. Our typical standard deviation is only 0.02 ppm!

The Model 5581 Bridge does a true auto-balancing procedure to nine significant digits. As the check proceeds, the bridge steps through an internal comparison of the transformer’s windings, the results of which are recorded to track its performance over time.

Another function of this bridge is its real-time uncertainty analysis program. In this mode you enter external uncertainty factors such as the uncertainty of your resistor, and the 5581 combines your information with its own uncertainties to compute a system uncertainty for your measurement.

The optional Windows-control software offers history logging and regression analysis along with uncertainty analysis and the auto-self-check feature. The software can record daily triple point of water readings for statistical prediction of your SPRT’s uncertainty. The program calculates standard deviations if you need them. You can enter coefficients for your SPRT and read temperature rather than resistance.

Of course, if you prefer, you can operate the bridge manually. The choice is yours, but either way you’ll find this to be a great bridge to use.

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