| 摘要 |
PURPOSE:To monitor a voltage drop of a power source without providing any source voltage monitoring circuit externally to an LSI circuit of an electronic clinical thermometer by detecting the oscillation frequency of an oscillation circuit when it oscillates with a reference resistance, and detecting the battery being flat. CONSTITUTION:A counter 19 counts up to measure the oscillation frequency. A gate 20 inputs output pulses from a crystal oscillator 11 to be inputted to a terminal 21 to a counter 22 on knowing by an electronic switch switching signal that a body temperature measuring oscillation circuit 7 oscillates at an oscillation frequency fs. A decode 23 monitors the contents of the counter 22 and resets a flip-flop 16 at a specific time to close a gate 17. Thus, the counter 19 counts output pulses of the body temperature measuring oscillation circuit 7 only for a specific time to measure the oscillation frequency. A comparator 24 compares the contents of a constant generating circuit 25 which generates the value of the counter 19 when the battery is flat with the count result of the counter 19 and outputs a battery flat signal to an LCD output terminal 13 when the battery is flat. |
