Tracking Water Consumption with Sensors

Water accounts for approximately 60% of a person’s body weight.   The human brain and heart contain an even higher percentage of water at over 73%[1].  It is important for people to drink the recommended amount of water each day in order to maintain proper hydration levels for optimal health. Unfortunately, an iDrink device to monitor our water consumption does not currently exist. There are a number of products one can buy on Amazon or at other retailers to monitor water consumption, but the measurement and tracking technology is too basic and imprecise. Current products only offer users a simple, timed reminder to take a sip based on their hydration profile and goals.

To get more meaningful water consumption tracking from a water bottle, it is essential to include sensors.  Pressure sensors are already used to monitor water level in ponds and tanks but are traditionally too big and expensive for consumer products.  Many bars integrate accelerometers into pouring spouts that are attached to each bottle to determine when a bar tender pours a drink (to monitor and prevent over-pouring).  As the bottle is tipped to pour, the accelerometer detects the bottle angle, and its input can be used to estimate the amount of liquor dispensed.

Mitsumi MMR920 pressure sensor is ideal for water level measurement in a smart water bottle due to its small size, low-cost, and liquid compatibility. It can be embedded at the bottom of the bottle to measure water pressure which is used to calculate water level (Stevin’s law).  The sensor simply measures the water level height.  The water level decreases as water is consumed and a microchip is able to quantify this change. Because this method calculates water consumption using the drop in water level, it works even when the water bottle is refilled.

Water bottles are typically used when a user is mobile – during travel, gym or sporting events they can be tossed around and are not always in an upright position. To accurately measure the water level, a second sensor is needed to compensate during situations when the bottle is inclined.  This is achieved by using a two-axis accelerometer to detect when and how much the bottle is tilted.  The tilting of the bottle is detected by the two-axis accelerometer and its signal can adjust the pressure sensor reading for improved accuracy.

Two-axis accelerometers are also used in smart phones to detect orientation and, coupled with a pressure sensor, offer an inexpensive solution for monitoring water consumption within smart water bottles.  The microchip interface enables data to be synced with a smart phone. Merging this data with each user’s own unique health profile (age, weight, fitness) and environmental statistics (humidity, temperature, time) makes it possible to determine the precise quantity and frequency of each individual’s water consumption needs.

1. The Water in You: Water and the Human Body | U.S. Geological Survey (usgs.gov)