Tamper detection methods and apparatus for load management terminals
US5488565A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 28, 1993 |
| Grant date | Jan 30, 1996 |
| Priority date | — |
| Expiry date | May 28, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R21/133
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Apparatus and methods are claimed for detecting tampering with a load management terminal, wherein the terminal has a load control relay coupled to a power line for selectably decoupling the load from the power line. One embodiment of the claimed apparatus for detecting tampering comprises a current sensor coupled to the load control relay for sensing whether load current is flowing through the load control relay contacts when the contacts are closed. A timer is provided for measuring elapsed time during which no current is sensed flowing through the closed contacts. An indicator provides an indication of tampering when the elapsed time measured by the timer exceeds a pre-determined time limit. Preferably, in this embodiment, the current sensor comprises a voltage detector coupled to the control coil of the relay for detecting whether an AC voltage has been induced in the control coil by the load current. In another embodiment, a voltage sensor is provided for sensing whether voltage is present across the contacts of the relay when the contacts are open. In yet another embodiment, a suitable resistance is connected to the power line in parallel with the load thermostat to ensure at…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.