Technical readss from Comtest
Gold Standard in electrical calibration – Fluke’s 5730A Multifunction calibrator
Fluke is offering what they are calling the “gold standard” of multifunction calibration – the very impressive 5730A high-performance multifunction calibrator.
- Improved performance specifications for ac voltage, ac current and resistance
- 6.5 inch CGA capacitive touch screen with full colour graphical user interface
- Visual Connection Management™ terminals guide cable connections
- Compatible with 52120A and 5725 amplifiers
- Full MET/CAT® compatibility with 5700A and 5720A procedures
- Artifact Calibration using 10V, 1Ω and 10kΩ external standards
Like its predecessors, the 5730A calibrates a wide range of digital multimeters, up to long-scale 8.5 digit DMM’s as well as RF voltmeters when equipped with the wideband option. But this model features improved specifications that will help users increase test uncertainty ratios (TURs) and increase test confidence. Also, the improved specifications will reduce the need for guardband, giving users confidence and peace of mind with calibrations.
The 5730A is designed for calibration professionals who require the most accurate dc/lf signals available in a multifunction calibrator. Metrologists in national laboratories, the military, third party calibration laboratories, and corporate users with high-end workload value the performance and reliability of the 5730A. All 5730A calibrators are traceable to international standards and are produced in the factory with ISO/IEC 17025 accredited calibrations. Specifications are stated to the standard Fluke Calibration 99% confidence level (as well as 95% confidence level) to support easy measurement comparisons, according to international quality standards. Specifications are absolute and include the uncertainty of the calibration standards used. No additional analysis is required.
The 5730A calibrator incorporates the latest technology, such as surface mount technology and modern digital components, that have enabled Fluke Calibration to advance the proven design of the 5700A/5720A and create the next generation of high-performance multifunction calibrators.
The 5730A keeps many of the front-panel details that characterize its predecessors while adding a new full-colour touch screen display to enhance usability and ease calibration. Users enter values via a familiar, calculator-style keyboard, working naturally from left to right. A graphical user interface features easy-to-read, easy-to-use menus, as well as access to common functions. Status indicators for OPERATE, STANDBY, and HAZARDOUS VOLTAGE appear on the screen in bright letters or icons - easily recognizable – even from across the calibration lab.
The redesigned front panel features many new improvements, like Visual Connection Management™ output terminals that light up to show which terminals are active, guiding the user to make the correct connections. The handles and knob are over-moulded for comfort and feel. USB ports are placed both on the front and rear of the unit. Use the port at the front to download internal calibration constants; use the rear port for remote communication with a PC—or choose the LAN, IEEE or serial interfaces.
The 5730A calibrator features Artifact Calibration. Only three artifact standards—a 10 V dc reference and 1 ohm and 10 k ohm resistance references—are required to calibrate all ranges and functions to full specifications. Front panel GUI instructions prompt the operator to make connections and inputs each step of the way. The calibrator controls the process, which takes only about an hour, compared to several hours using traditional calibration methods. In addition to saving time and equipment costs, Artifact Calibration can extend the time between calibrations of the 5730A to two years before a full verification check by a Fluke Service Center is required. And, because the 5730A can tolerate operating temperatures between 15 °C and 35 °C, it can be calibrated where it’s used, rather than having to be shipped to a standards laboratory for calibration.
When Artifact Calibration was first introduced in the Fluke 5730A, customers asked many questions about traceability because they were surprised that one could calibrate so many ranges and functions with only three external standards. However, thanks in part to considerable testing and evaluation by three national laboratories in Europe, Artifact Calibration is fully validated by the metrology community. Today many metrologists rely on Artifact Calibration to maintain their Fluke calibrators at 90-day specifications for up to two years. Significant savings can be realized in calibration costs by only performing a full verification at a certified Fluke Service Center every two years. The time savings are also significant, as Artifact Calibration allows the 5730A to remain in service and conducting calibrations when it would otherwise be unavailable due to shipping and service time.
For extra confidence that the 5730A calibrator stays within its specifications between calibrations, the built-in automated Cal Check function checks every range and function against a set of dedicated internal standards to monitor the drift of each. These Cal Check results can be downloaded to a computer via the USB port conveniently placed on the front of the unit to develop control charts predicting the calibrator’s long-term performance. It may be surprising to learn that the internal standards built into every 5730A are the functional and design equivalents of a Fluke 732B 10 V reference plus two fully characterized metrology-grade resistance standards. These standards—totally separated from the output circuitry—are not used in normal operation and are provided solely to provide a check.
The most prevalent long-scale digital multimeters in the world are the Fluke Calibration 8508A and the Agilent 3458A. Due to the high level of accuracy of these two 8.5 digit DMMs, there are several points where calibration professionals are forced to use a technique known as guardbanding. This method decreases the measurement uncertainty for a particular value to guarantee the calibrated value falls within the appropriate 99% or 95% confidence interval. In designing the 5730A, Fluke Calibration worked diligently to bring users even better performance specifications to help address some of these “problem points.”
High current output to 120 A
Paired with a Fluke Calibration 52120A Transconductance Amplifier, the 5730A can output up to 120 A, and display the output on the 5730A touch screen display. Operating in closed-loop mode with the 52120A, the 5730A maintains the best current accuracy over the widest range of calibration workloads. The 5730A is also compatible with the Fluke Calibration 5725A Boost Amplifier.
As mentioned earlier, it has been become increasingly difficult to always meet the industry-recognized test uncertainty ratio (TUR) of 4:1. To minimize the chance of approving an out-of-tolerance (OOT) condition during calibration, the practice of guardbanding is employed. As all measurements are subject to error, most measurements assume a normal distribution commonly referred to as a “bell curve.” When the TUR is less than 4:1, the error band of the unit under test (UUT) is small enough that the calibrator cannot guarantee that the measurement is within specification. In Figure 1, the uncertainty bell curve is shown at the upper specification limit of a UUT. There is a 50 percent chance that the measurement is OOT, and 50 percent that it is in tolerance. To protect the metrologist, guardbanding moves the specification limit closer to the nominal value to “guard” against the possibility of approving an OOT condition. As shown in Figure 1, the measured value must now fall within a smaller offset from the nominal value, providing 95 percent confidence that the actual value is within the specified band. This gives the metrologist the confidence that the measurement is accurate. The 5730A calibrator is the most accurate dc/lf calibrator available, but it still requires the use of guardbanding for the most demanding long-scale multimeters.