There are failsafes, failsafes and failsafes...

[C6C6CH3vo]

Classic design, simple, but pitot like approach as been proven for 100 years (carbys). Now can someone please tell me what the green wire outputs? thanks

[Richard L]

Originally Posted by lemmonhead

Everyone must realize that this type of flow meter is a measure of VOLUMETRIC flow rate and is used for reliability and repeatability purposes. It is NOT, i repeat NOT MASS FLOW rate which would be the actual mass of fluid per unit of time.
Do you see that restriction in the middle. it is there so you can measure pressure differential. Mathmatically the differential pressure is a square of fluid velocity. Differential type flow meters need corrections for temperature or pressure changes which I think most if not all systems do not do this.
why dont meth injection company's make a MASS flow meter like the Coriolis method or thermal mass meter.

In this type of fluid application, we can only measure volume unless you incorporate a kitchen scale into the sensor. As you have mentioned, the most important is repeatability.

The sensor is a based on an magnetic turbine wheel, rotational speed is picked up by a Hall effect sensor in the middle. The machined slot is for allowing the sensor to get closer to the wheel. It is not a restrictor. See the transparent sensor tube - water is spun around the surface of inner bore to ensure maximum turbine/fluid contact. An Aquamist design we have copyright to, we manufacture them in house.

I am afraid your maths does not apply to this sensor. Nonetheless, it is a nice bit of information.

[Richard L]

Originally Posted by C6C6CH3vo

Classic design, simple, but pitot like approach as been proven for 100 years (carbys). Now can someone please tell me what the green wire outputs? thanks

The green wire ... is for calibrating the flow sensor's dynamic range to a fix output over a large flow range. (0-5V)

A turbine based wheel flow sensor's rotational speed is not linear to flow, this is due to variation of fluid molecules hitting the turbine in a random fashion. This is particually notable in this type of applications, where flow is affected by the pressure ripple from the pump diaphragm. We don't have the luxury of a pulseless supply.

As the DDS3 is designed to be a universal flow monitoring device, we have to overcome some of the extreme pressure pulses from a PPS system. Particularly between the low DC% and high DC%. Low DC have well spaced out ripples and high DC has the "on-demand" induced ripples (as much as 20psi).

In order to give a reasonable accuracy over all type of systems, we mapped the turbine speed against the actual flow, over several flow ranges (a lot as we are extending the flow range). Each range is stored inside the mircochip. When you put different voltages into the green wire, it is like turning pages of the stored files. Other house-keeping algorithm is also employed to keep the data processing stable.

I cannot explain the green wire's function in a less complicated way.

[C6C6CH3vo]

Got the picture, thank you