| 摘要 |
PURPOSE:To detect pressure exceeding the strain limit of a piezoelectric element securely by applying a voltage in such a way that when the strain of the piezoelectric element detecting pressure has a limit value, the strain is corrected. CONSTITUTION:When an FF21 is inverted by operating a switch S, an OR circuit 5 is opened and an AND circuit 4 is closed through an inverter 22 to inhibit data transfer from a timer circuit 3 to a display part 6. A voltage signal of pressure from the piezoelectric element 7 is sent through an AD converter 11, pressure converting and adding circuit 13, and OR circuit 20 to the display part 6 to display the pressure. The output of the AD converter 11, on the other hand, is sent to a comparing circuit 13 and compared with the strain limit voltage Va of the piezoelectric element 7; when it exceeds the Va, a signal is generated to reset and FF15, and consequently an MOS transistor 9 is turned on to apply the Va from a power source 8 to the piezoelectric element 7 in such a direction that the strain is corrected. The circuit 12 adds the Va to the input signal and the sum signal is converted into pressure, which is sent to the display part 6. Thus, pressure exceeding a strain limit is detected securely. |
