| 摘要 |
In flow technology - for example in liquid chromatography - it is sometimes necessary to meter very small solvent flows which are at high pressure. The micro-metering valve to be patented provides, in combination with the solvent-independent thermal-pulse measuring system to be patented, a possibility to meter a solvent stream rapidly and virtually without inertia. The micro-metering valve comprises a passive valve system whose locking direction is opposite to the flow direction. A piezo-resistive element seals said valve system completely as a result of being deflected in the counter-flow direction. By controlling the deflection of the piezo-resistive element, it is possible to effect a change of the flow resistance of the micro-metering valve and thus metering of the liquid stream. The appertaining flowmeter system, which is based on a measurement of thermal pulses, comprises, as the thermal pulse emitter, a PELTIER element which generates a steep temperature gradient by active cooling prior to the thermal pulse, without supplying an unduly large amount of heat to the solvent even if pulses follow each other rapidly, since the mean amount of heat of the solvent is altered to only a disproportionately small degree compared to the temperature rise of the pulse. A low-axial-delay measuring section in the high-pressure range between the thermal pulse emitter and the thermal pulse sensor system results in the temperature gradient generated being maintained.
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