Circuit arrangement for processing signals from volume flow sensors in accordance with the vortex detachment process

摘要

The invention relates to a circuit arrangement for processing signals from volume flow sensors in accordance with the vortex detachment process, particularly for measuring volume flows in the field of artificial respiration and anaesthesia. The aim and object consist in that the vortex signals contained in the output signal of the vortex detector are also reliably detected and processed in a range having a signal/noise ratio of < 10 dB, in order to detect respiratory volume flows within a measuring range of 5 l min<-1>...200 l min<-1>. According to the invention, this is achieved by the fact that the frequency-analagous signal is supplied, on the one hand, via a low-pass filter and an amplifier to a first trigger, and on the other hand, directly to a second trigger. Both triggers are located at the inputs of an electronic change-over switch which is connected to a frequency/voltage converter followed by a third trigger. The cut-off frequency of the low-pass filter is dimensioned in such a manner that it only passes and filters frequencies with a signal/noise ratio of < 10 dB and these are amplified so that error-free squarewave pulses can be obtained.