| 摘要 |
A circuit for measuring the internal impedance of the cell of a heart pacer in order that the remaining life of the cell can be estimated. The test is performed by cutting off all current flow from the cell to the pacer circuitry, the pacer still being powered, however, by the conventional by-pass capacitor. When the cell impedance test is conducted, a test capacitor is placed across the cell and it charges exponentially with a time constant which is a function of the cell impedance. By measuring the time required for the test capacitor potential to reach a reference level, the cell impedance can be ascertained. The measured parameter can be telemetered out of the pacer along with other data in the conventional manner. With a typical lithium iodide cell, the internal impedance of the cell varies from less than 100 ohms when new, to tens of kilohms near the end of the cell life.
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