567 MAIN ST OCONTO, WI 54153 Get Directions
567 MAIN ST OCONTO, WI 54153 Get Directions
When Holt developed the first AC voltage calibrators in 1958, the only available Thermal Transfer Voltmeter was the Hermach Englehard instrument developed by F.L. Hermach at NIST in the early 1950's. This was an excellent instrument for its time, but it soon became apparent that a TVM with better resolution, stability, and frequency response was needed. Holt engineers developed the Holt Model TV-1, which was submitted to NIST for testing in July of 1960. This instrument was the basis for United States patent 3,258,691, which covers the earliest use of multiple thermal junctions for the reduction of DC reversal, the use of a thermal converter in the feedback loop of an operational amplifier to obtain a linear conversion to DC, the use of precision zener references in a TVM, the use of a coaxial transfer switch in a TVM, and the use of a coaxial range attenuator in a TVM. Many of these instruments are still in use today and are considered state-of-the-art.
As the calibration laboratory workloads continued to increase, Holt recognized the need for a TVM with thermo-element burnout protection, and introduced the Model 6 in 1963. This was followed by the Model 6A in 1965. The 6A included an electronic null detector and lindeck potentiometer of high resolution and low noise allowing comparisons of better than 20 ppm. Holt also led the way in alternating current metrology with the introduction of the HCS-1 Shunt set in 1961. These units are still the best in the world today. Improvements in these designs have been made by Holt over the past thirty years, but many of these early instruments continue to serve as reference standards in laboratories around the world.
Continuing research has enabled Holt to automate the AC/DC measurement while improving the resolution and stability of our transfer voltmeters. Allowing measurement repeatability of better than 5 ppm., these fully-protected instruments cover the full voltage and frequency ranges of today's AC Calibrators.
Today, as a direct result of this long history of excellence, Holt's products are the finest available. The continued commitment of Holt personnel provides the best in metrology and service to our customers.
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