SLIA097 March   2022 DRV5011 , DRV5011 , DRV5012 , DRV5012 , DRV5013 , DRV5013 , DRV5015 , DRV5015 , DRV5021 , DRV5021 , DRV5023 , DRV5023 , DRV5032 , DRV5032 , DRV5033 , DRV5033 , TMAG5110 , TMAG5110 , TMAG5111 , TMAG5111 , TMAG5123 , TMAG5123 , TMAG5231 , TMAG5231 , TMAG5328 , TMAG5328

 

  1.   Trademarks
  2. 1Introduction
  3. 2Flow Meter Design
    1. 2.1 Mechanical Considerations
    2. 2.2 Magnetic Considerations
      1. 2.2.1 Material
      2. 2.2.2 Geometry
      3. 2.2.3 Magnetic Deign Tools
    3. 2.3 Hall-Effect Sensor Considerations
      1. 2.3.1 Device Sensitivity
      2. 2.3.2 Unipolar Switch
      3. 2.3.3 Omnipolar Switch
      4. 2.3.4 1D Latch
      5. 2.3.5 2D Integrated Latch
      6. 2.3.6 Bandwidth
      7. 2.3.7 Package
      8. 2.3.8 Power Consumption
  4. 3Flow Meter Development
    1. 3.1 3D-Print Recommendations
    2. 3.2 Flow Meter Assembly Considerations
    3. 3.3 Flow Meter Assembly Guide
      1. 3.3.1 Shaft Installation
      2. 3.3.2 Bearing Installation
      3. 3.3.3 Magnet Installation
      4. 3.3.4 Impeller Installation
      5. 3.3.5 O-ring Installation
      6. 3.3.6 Flow Meter Top Installation
      7. 3.3.7 PCB Mounting
      8. 3.3.8 Cover Installation
  5. 4Flow Meter Evaluation
    1. 4.1 Flow Meter Testing
  6. 5Error Sources
    1. 5.1 Mechanical Error
    2. 5.2 Sampling Error
    3. 5.3 Magnetic Error
  7. 6Flow Meter PCB
    1. 6.1 PCB Schematic
    2. 6.2 PCB Layout
  8. 7Bill of Materials (BOM)
  9. 8References

1 Introduction

Mechanical flow meters monitor the rotational speed of an impeller to interpolate the rate of fluid movement. When implemented with a magnet, the rotational speed of the impeller can be measured via changes in magnetic field through the use of Hall-effect sensors. This implementation has primary advantages of retaining the waterproof nature of the mechanical design, while also allowing for accurate measurements for rotational speed. The output of the Hall-effect device can then be connected to a microcontroller for frequency to flow rate conversion.

The flow meter design detailed in this document was created to offer an inexpensive test system capable of evaluating various magnet and Hall sensor configurations. In total, there are three primary configuration options for the 3D printed flow meter. Additionally, each configuration option is capable of evaluating various Hall sensors, including One-Dimensional (1D) and Two-Dimensional (2D ) SOT-23 devices. See Section 3.2 for the download link and for instructions for creating the 3D printable mechanical flow meter.