MAXREFDES70#: Temp / TOF Flow Rate Sensing

Accurate, cost-effective, ultrasonic flow meters key a transformation in liquid and gas flow measurement. Critical for revenue collection, leak detection and conservation of critical natural resources, flow meters lie at the heart of utility and industrial distribution systems of water, gas and heat. Mechanical flow meters, currently the most prevalent meter style, use moving parts to measure the velocity of a fluid in a pipe. These moving parts are subject to wear and lose accuracy over time, often requiring replacement within 10 years1. The MAXREFDES70# ultrasonic time-of-flight flow meter by Maxim Integrated sends and receives ultrasound waves between piezoelectric transducers in both the upstream and downstream directions in the pipe. By measuring the TOF difference between the upstream and downstream wave travels, utilizing sophisticated digital signal processing techniques, a very accurate flow rate can be calculated.

The MAX35101 is the center of the heat/flow meter system. The MAX35101 integrates all the functions required for automatic TOF measurements, including the ultrasound pulse launching and detecting, TOF calculation, temperature measurement, and a real-time clock (RTC). The MAX35101 can work in various configurable automatic event timing modes, requiring very minimal interactivity from a host microcontroller, thus reducing the total power consumption of the system.

The MAXREFDES70# reference design (Figure 1) demonstrates the typical application of the MAX35101 TOF converter. Please note, the meter is not calibrated and only serves as a high-performance platform for developing customized heat/flow meters. Contact the manufacturer for calibration details.