Thursday, June 11, 2015

Teardown of a paddle wheel flow meter

I'm setting up a control system for a small scale biofuel processing rig. Part of the task is to monitor the flow rate of feedstock. Due to budget constraints, I could not simply buy and industrial grade sensor. So, I'm evaluating this low cost sensor for low flow rate and more viscous fluid [than water].

This type of low-cost paddle wheel flow meter is sold by Adafruit among other places.

Assembled flow sensor before teardown

Cavity is open.  Top of the paddle wheel with the magnet visible inside the cavity.
The gap between the tips of the paddles and the cavity is about 2.5mm .  If the gap were smaller, this flow meter would be more sensitive at low speeds.

The static o-ring, which seals the paddle wheel cavity, is visible on the lid.  The latter also serves as the bottom of the PCB compartment.

At the end of the paddle wheel sits the magnet.  The outside diameter of the magnet is 9.7mm .

PCB compartment is open.  Component side of the PCB visible.

PCB with Hall effect sensor removed from its compartment

On the left side of the PCB stands the Hall effect sensor.  The writing on the IC is "W130".  I'm guessing it's Winson WSH130 (datasheet).  The Hall effect sensor sits 16.4mm from the axis.

The o-ring in this photo prevents liquid ingress into PCB compartment.  This is the 2nd o-ring in this device, and not the main one that seals the paddle cavity.


After this teardown, the reassembled sensor continued to work like new. 


Sensors Magazine article on paddlewheel flow sensors
Higher precision paddle wheel flow sensors made by Omega Engineering


I'm not affiliated with any of the companies mentioned in this post.

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