Measurement setup and adjustment
The centerpiece as a reference is a special, high-precision ultrasonic flowmeter in the form of the Keyence FD-Q10C. This clamp-on flowmeter operates completely contact-free and also does not affect the flow in the circuit. The accuracy exceeds that of the mechanical solutions by far, so that a real reference value for the instantaneous volume flow is obtained here after calibration. Especially also in the lower ranges clearly below 100 l/h.
The whole thing is powered via a special 4-pin M12 cable from an external power supply. In order to do exact justice to the tube section used under the clamp, I had the assembled components calibrated once again in a friendly laboratory in series connection to a calibrated device (M 1). Instantaneous volume flow is generally measured in liters per minute (l/m), not per hour. In addition to limit value determination, the instrument also offers differential measurements and a freely definable zero point.
Equipped in this way, it is now possible to evaluate flow sensors in the measuring circuit and, for the multiple value determination, always also have the option of comparing in real time between this test object and the reference sensor in order to detect a possible drift in the volumetric flow and, if necessary, readjust something. The heart of the measurement setup is again a potent pump that can deliver up to 300 l/h, a large expansion tank in the compressor cooler and an external one with a combined volume of almost 10 liters (here I have again reduced the amount of water somewhat), as well as the compressor cooler itself, whose hysteresis has been adjusted so that the temperature in the flow can be kept between 19.5 and 20.5 °C up to 1000 watts of supplied waste heat. Pure osmosis water without additives is used.
To avoid fluctuations of the volume flow (“flow rate”) in the area of the pump, I let it run unregulated at maximum power and instead regulate the volume flow down with the help of a spindle valve in cooperation with a ball valve as valves arranged in parallel. With the ball valve, I set (quite roughly) the flow rate slightly below the desired value and then regulate the flow rate exactly to the desired value by opening the very well controllable spindle valve.
the stem valve is far too restrictive on its own, so with the ball valve closed (or not) I can only measure flows from around 100 l/h upwards. However, this can then be adjusted very precisely down to 10 l/h almost steplessly.
I have installed all three sensors in series and between the “High Flow Next” and the Alphacool ES sensor put another 10 cm straight hose to exclude turbulence. I also had the Alphacool sensor for counter-testing once before the Keyence and these values coincided with those of the setup at the end of the chain. Thus, it does not matter where which sensor is integrated.
Alphacool ES "HighFlow", Durchfluss- und Temperatursensor mit Tachosignal (17558)
Zentrallager: >5 Stück bestellt, wird in 2 Werktagen erwartetFiliale Wilhelmshaven: >5 Stück bestellt, wird in 2 Werktagen erwartetStand: 28.03.24 23:03 | 39,57 €*Stand: 28.03.24 23:06 | |
lagernd: 250+ | 39,58 €*Stand: 28.03.24 23:00 | |
Alphacool | ab Lager verfügbar | 39,98 €*Stand: 28.03.24 23:06 |
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