| 摘要 |
1,086,628. Measuring mass flow rate of gases. WESTWIND TURBINES Ltd. March 10, 1966 [April 2, 1965], No.14026/65. Heading G1N. The mass rate of flow of a gas is measured by integrating square pulses having a repetition frequency, duration and amplitude linearly proportional to a respective one of the quantities volumetric flow rate, pressure and the inverse of the temperature of the gas. The gas flows past a turbine having gas lubricated bearings, causing it to rotate at a speed proportional to the volumetric flow-rate of the gas thereby generating pulses at a corresponding frequency by means of a magnetic or capacitive pick-off. These pulses after shaping are supplied to a bi-stable circuit to generate a further series of pulses of the same frequency. Each of the latter pulses is terminated by a feedback circuit including a time constant circuit and a level discriminator supplied with signals from the time constant circuit and from an amplifier connected to a copper resistance thermometer (or a thermocouple). The length of the pulses is thus made inversely proportional to the gas temperature. The pulse amplitude is then controlled in accordance with the output of a further amplifier receiving the output from a diaphragm-type pressure transducer including a strain gauge or an inductive pick-off. The resulting pulses are finally supplied to a moving coil meter. The output may be modified as a function of standard pressure and temperature so that the device indicates the flow rate in units of standard volume for a particular gas. The measuring circuit may also include means for modifying the output in accordance with a selected value of R, the gas constant, so that the device may be used for any gas. |
