Digital time meter
US4478521A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 9, 1981 |
| Grant date | Oct 23, 1984 |
| Priority date | — |
| Expiry date | Nov 9, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG04F10/04
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A digital time meter for use in a vehicle or other motorized equipment for sensing, accumulating, displaying and retaining the total time a monitored signal from the vehicle or the equipment is present employs a crystal oscillator time base to time the monitored signal. The meter uses integrated circuits to count pulses emanating from the time base in order to accumulate the total time the monitored signal is present. These integrated circuits also have decoder/driver circuitry with multiplexing capabilities to operate a digital display. Power to operate the meter is obtained from the monitored signal when said signal is present, and a replaceable internal battery when said signal is absent. The battery can be replaced without affecting the timing and accumulating functions of the meter provided the monitored signal is present. When the monitored signal is absent, a display switching circuit disables the display to prolong battery life. The meter can retain the accumulated time for several years on battery power alone. The digital display can be detached from the meter to prevent unauthorized reading of the display and to protect the display from physical damage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.