| 摘要 |
<p>PURPOSE:To provide a liquid detector for detecting a liquid within a pipe of a small diameter entirely without requiring any severe adjustment by fixing a nonconductive pipe concentrically with a tubular conductor serving as a detection probe and a shield probe, respectively, on the inside and outside thereof and detecting variation in the capacitance caused by the passage of fluid by means of the detection probe. CONSTITUTION:A pipe 1 is fixed concentrically with a sensor head part 10 comprising a tubular conductor and a coaxial cable serving as a probe 11 and a shield probe 12, respectively on the inside and outside thereof, is connected through an extension cable 30 with an amplifier section 20. At the amplifier section 20, an oscillator 21 drives the probes 11, 12 with the same phase and amplitude to sustain the potential difference substantially at zero level. In that state, variation DELTAT of oscillation period caused by the capacitance of liquid in the pipe 1 is detected and converted through T/V conversion into a voltage signal which is then compared 23 and a signal representative of presence or absence of liquid is outputted 24. This detector can be fixed easily to a medical apparatus of a small diameter and applicable to any liquid because of the difference in dielectric constant between air and the liquid. It is also suitable for automation because of easy adjustment.</p> |
