By Martin Rowe, senior technical editor, test & measurement, EE Times & EDN
We normally think of technology as fast-moving — what’s new today is yesterday’s news a few microseconds later. In the calibration/metrology business, new means “unproven.” That’s why metrology-grade products come to market rather infrequently. Fluke Calibration has introduced two metrology-grade 8.5-digit digital multimeters (DMMs): the 8588A reference multimeter and a subset, the 8558A . Fluke’s original 8.5-digit DMM, the 8508A , was released in 2013.
When you need the most accurate and stable measurements for calibrating multifunction calibrators that, in turn, calibrate working test equipment, the 8588A reference multimeter offers what Fluke claims is the most stable meter on the market at one-year DC voltage accuracy of 2.7 µV/V at 95% confidence interval (3.5 µV/V at 99%). Fluke also claims 24-hour stability of 0.5 µV/V (95 %) or 0.65 µV/V (99 %).
While these stability specs are slightly better than those of the 8508A, the 8858A lets you achieve an 8.5-digit reading in 1 s. In addition, the 8858A adds capacitance, frequency, and RF power measurements to its DC/AC voltage/current, resistance, and temperature (with optional PRT probe) measurements. Capacitance and RF power measurements require a power sensor. Fluke recommends the Rohde & Schwarz NRP series.
A companion meter, the 8558A, is a scaled-down version of the 8588A. Its DC voltage in the 10-V range is 4.0 µV/V at 95% confidence interval. It also lacks the capacitance and RF power measurements.
When running at 4.5 digits, these meters can make 100,000 readings/s. Data transfer rates to a host computer reach 500,000/s over USB and 200,000/s over Ethernet or GPIB. Data transfer speeds depend on the data format.
The USB and Ethernet ports are new for both models, giving you additional connectivity options over the older 8508A. Front-panel USB ports let you load configurations and store measurement results. When operated under remote control, both models can emulate the Fluke 8508A and the Keysight 3458A, meaning you can use existing applications without writing new code. Of course, you can take advantage of the new features available in these meters as well.
Both models add usability features over the older 8508A. For example, the new models feature graphical displays that let you see digitized waveforms from their 5 MS/s digitizers. The higher-end 8588A also lets you see measurements in the frequency domain through a fast Fourier transform (FFT).
As with the 8508A, both the 8558A and 8588A are available with an optional set of rear binding posts. The rear set lets you connect to an instrument under calibration in a rack without the risk of people accidentally removing cables. Furthermore, the second set lets you make ratiometric measurements for comparing measurements to a reference source. An illuminated binding post help guide technicians to connect test leads to the correct locations.
When it comes to metrology-grade instruments, it’s all about the specs, too many to mention here. Follow the links above to the respective datasheets.
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