Knopp, Inc.

knoppAbout Us.

Knopp Inc., a TESCO company, is a design and manufacturing company located in Bristol, Pennsylvania outside of Philadelphia.

We build high quality precision voltage and current transformers, electric meter and transformer test equipment, and electrical instruments for the utility and electrical industries. Our voltage and current transformer test equipment is used by electric utilities throughout the world to verify the accuracy of transformers used to measure electric energy.





Knopp, Inc., was founded in 1928 in then Oakland, CA, by Otto Knopp under the name Electrical Facilities.  Mr. Knopp (pronounced KAH-NOPP) was the Chief of the Bureau of Tests and Inspection at Pacific Gas & Electric.  He had observed a need for some specific types of products and test equipment which were presently going unfilled, and decided to begin the manufacture of some of this equipment himself.

The company was just beginning to get underway from its small, conservative start when the crash of 1929 occurred, followed by the Great Depression.  This caused years of struggling to keep the business going with year after year of operating losses, yet Mr. Knopp continued patenting his inventions and designing new products for the fledgling company.

In 1932, Mr. Knopp’s son Harold joined the firm.  In 1936 the company made its first operating profit—a whopping $750!  In 1943 Mr. Knopp’s daughter Helen joined the firm. Harold and Helen Knopp continued to operate the company after Mr. Knopp’s death in 1946. In 1957 the company moved to Emeryville, CA, and continued manufacturing quality, precision items to a global market.

In 1976, Harold and Helen decided to retire and they sold the majority of their shares of Knopp Inc. to Quantum-Precision Inc., a company that had been established by two former Sangamo Electric Company employees—Alexander Finlay and Ralph W. Karle. Mr. Karle passed away in 1996, and Mr. Finlay passed away in 2017 leaving the future of the company uncertain.

In 2018, TESCO – The Eastern Specialty Company acquired Knopp and continues Mr. Knopp’s legacy of building quality, precision products for use all over the world today.

In 2021, Knopp moved to Bristol, PA, current headquarters and manufacturing facility of TESCO – The Eastern Specialty Company.



Current Transformer Testing Systems and Standards

Voltage Transformer Testing Systems and Standards

Hand Instruments


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