Practical Arduino: Cool Projects for Open Source Hardware

Chapter 10. Water Flow Gauge

Determining the consumption of a resource that is measured in units of volume can be more tricky than it sounds. Use of resources such as water, gas, and even electricity is typically measured by gauges that determine either instantaneous flow rate or cumulative volume over time. Both techniques have problems. Measuring flow rate at frequent intervals allows you to do time-based reporting and generate a graph of how the flow rate varied over time, but to determine the total consumption by volume across a specific time period, you then have to integrate the data. This means there is the danger of underreporting usage if your sample rate is slow and usage rapidly fluctuates or spikes. Measuring cumulative volume makes ...