| 摘要 |
A telemetry system is described in which a plurality of channels are coupled to a bus. A control subsystem controls the channels so that one of the channels presents to the bus during its designated time period a channel characteristic. The control subsystem interrogates in the analog domain each of the channels during its designated time period, and forms a signal representative of the channel characteristic. The control subsystem may combine one or more of the signals into a digital packet, and transmit the same over a network. Each channel in the telemetry system can include a sample-and-hold circuit, a variable resistor circuit, and a control element. The sample-and-hold circuit is configured to hold a sample of a signal. The variable resistor circuit is configured to present a variable impedance to one or more signal lines during a time period designated for the channel an impedance representative of the sample held by the sample-and-hold circuit. The control element is configured to control the variable resistor circuit to present to the one or more signal lines an open circuit equivalent impedance during times other than the time period designated for the channel. In some implementations, the channel also includes a switch which decouples the sample-and-hold circuit from the variable resistor circuit during times other than the time period designated for the channel. In some implementations, the control element is a programmable control element that is programmable with a unique channel identifier, and may include a timing element which is updated responsive to a control signal. The programmable control element determines that the designated time period for the channel is occurring or will occur based on a comparison of the contents of the timing element with the unique channel identifier. The control element can be a zero power control element. |
