Issued Patents All Time
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4937520 | Instrument to measure the errors of apparent power meters | Piotr S. Filipski, John J. Zelle | 1990-06-26 |
| 4786859 | RMS measuring apparatus for AC/DC voltages | John J. Zelle | 1988-11-22 |