thermal consumption meter falsification prevention circuit - uses same cable for data transfer and heater control and passes sensor signals to sample-and-hold circuit

摘要

The electrical circuit for a thermal consumption meter has a temp. sensor near a heating body and a corresp. electrical connector between sensor and meter which is designed to prevent fraudulent alteration to or falsification of the measurement results. The electrical cable used to transfer the temp. sensor signal is also used to deliver the electrical power to the valve which must be electrically opened to permit the flow of heat to the heating body. The valve current circuit and temp. sensor output transfer current circuit have different current directions. The polarity of the transfer circuit is periodically switched accordingly. The transferred sensor signals are stored using either an analogue sample-and-hold circuit or an analogue-to-digital converter.