| 摘要 |
PURPOSE: To obtain measurement result of high precision by, at measuring gas concentration with an ultrasonic wave device when the gas flow coming from an entrance is split and made to flow in a housing, suppressing a gas flow turbulence and performing temperature compensation. CONSTITUTION: To an ultrasonic wave transmitter 6 of a gas sensor 1 in the gas flow which flows as a laminar flow in a housing, a rectangular wave signal is sent from an oscillator/driver 30, to generate ultrasonic wave, and, a rectangular wave signal representing reference output is, through a circuit line 31, sent to a comparator 36. Meanwhile, an ultrasonic wave reception element 7 receives ultrasonic wave, and in its sine wave output signal, a rectangular wave is, through an amplifier 33, inputted in a phase shift circuit 35, and then phase- shifted and inputted in the wave form comparator 36. The comparator 36 compares a gas sensor output and a phase shift signal to a reference output signal, to detect a phase shift between two signals (proportional to gas concentration), and the output difference is wave-filtered with a filter 39 and converted into a volt, and temperature compensation is made at a circuit 41, and then a span representing pressure difference is corrected at a signal adjusting circuit 43, and outputted from a circuit line 44. |
