Methods and apparatus for fluid flow measurement

Abstract

A fluid flow meter estimates the velocity of water or another fluid flowing through pipe by comparing measurements of the water velocity to one or more pre-determined templates. The fluid flow meter may collect measurement signals from one or more flow sensors, estimate the fluid velocity or flow rate by comparing the measurement signals to the template, and either store the comparison results in local memory, transmit the results to a remote memory or server, or both. In some embodiments, the fluid flow meter transmits the results to a server via a wireless interface. The transducers and processing system can be powered by a battery, a power line, or, for manifolds installed outdoors, a solar cell. Example transducers and processing systems may also have a passive wake-up feature for power reduction; that is, they may only draw power when water or another fluid flows through the pipe.

What is claimed is: 
     
         1 . A fluid flow meter comprising:
 a sensor to detect an ultrasonic signal representative of a velocity of a fluid flowing through a lumen and to provide a measurement signal representative of the velocity;   a memory to store a template associated with a possible velocity of the fluid; and   a processor, communicatively coupled to the sensor and to the memory, to perform a comparison of the measurement signal to the template and to determine an estimated velocity of the fluid based on the comparison.   
     
     
         2 . The fluid flow meter of  claim 1  wherein the sensor comprises:
 (i) a first transducer to transmit the ultrasonic signal through the fluid flowing through the lumen; 
 (ii) a second transducer to receive a reflected, scattered, or transmitted copy of the ultrasonic signal; and 
 (iii) a front end to produce the measurement signal from the reflected, scattered, or transmitted copy of the ultrasonic signal. 
 
     
     
         3 . The fluid flow meter of  claim 2  wherein:
 the ultrasonic signal is a first ultrasonic signal, 
 the second transducer is further configured to transmit a second ultrasonic signal through the fluid flowing through the lumen, 
 the first transducer is configured to receive a reflected, scattered, or transmitted copy of the second ultrasonic signal, and 
 the front end is further configured to produce the measurement signal based on a difference of the reflected, scattered, or transmitted copy of the first ultrasonic signal and the reflected, scattered, or transmitted copy of the second ultrasonic signal. 
 
     
     
         4 . The fluid flow meter of  claim 1  wherein the memory stores a plurality of templates, each template in the plurality of templates corresponding to a different possible velocity of the fluid flowing through the lumen, and wherein
 the processor is further configured to compare the measurement signal to each template in the plurality of templates. 
 
     
     
         5 . The fluid flow meter of  claim 1  wherein the template is produced at a first sampling frequency and stored in the memory at a second sampling frequency lower than the first sampling frequency. 
     
     
         6 . The fluid flow meter of  claim 1  wherein the processor is further configured to interpolate at least one of the measurement signal and the template before or while performing the comparison. 
     
     
         7 . The fluid flow meter of  claim 1  wherein the processor is further configured to add a first random waveform to the measurement signal and a second random waveform to the template before performing the comparison. 
     
     
         8 . The fluid flow meter of  claim 1  further comprising:
 a fixation device to secure the sensor to a vessel that defines the lumen. 
 
     
     
         9 . The fluid flow meter of  claim 1  further comprising:
 a manifold defining the lumen, the manifold comprising:
 an inlet to channel the fluid into the lumen; and 
 one or more outlets to channel the fluid out of the lumen, 
 
 wherein the sensor is configured to measure the velocity of the fluid flowing into or out of the lumen. 
 
     
     
         10 . The fluid flow meter of  claim 1  further comprising:
 a communications interface, communicatively coupled to the processor, to transmit a representation of the estimated velocity or the measurement signal to a server. 
 
     
     
         11 . A method of estimating a velocity of a fluid flowing through a lumen, the method comprising:
 (a) acquiring a measurement signal representative of the velocity of the fluid flowing through the lumen;   (b) performing a comparison of the measurement signal to a template associated with a possible velocity of the fluid; and   (c) determining an estimated velocity of the fluid based on the comparison.   
     
     
         12 . The method of  claim 11  wherein (a) comprises:
 (i) transmitting an ultrasonic signal through the fluid flowing through the lumen; 
 (ii) receiving a reflected, scattered, or transmitted copy of the ultrasonic signal; and 
 (iii) producing the measurement signal from the reflected, scattered, or transmitted copy of the ultrasonic signal. 
 
     
     
         13 . The method of  claim 11  wherein (a) comprises:
 (i) transmitting a first ultrasonic signal in a first direction through the fluid flowing through the lumen; 
 (ii) receiving a reflected, scattered, or transmitted copy of the first ultrasonic signal; 
 (iii) transmitting a second ultrasonic signal in a second direction through the fluid; 
 (iv) receiving a reflected, scattered, or transmitted copy of the second ultrasonic signal; and 
 (v) producing the measurement signal from a difference between the reflected, scattered, or transmitted copy of the first ultrasonic signal and the reflected, scattered, or transmitted copy of the second ultrasonic signal. 
 
     
     
         14 . The method of  claim 11  further comprising, before (b):
 generating the template at a first sampling frequency; and 
 sampling the template at a second sampling frequency lower than the first sampling frequency. 
 
     
     
         15 . The method of  claim 11  further comprising, before (b):
 adding a first random waveform to the measurement signal; and 
 adding a second random waveform to the template. 
 
     
     
         16 . The method of  claim 11  wherein (b) comprises:
 comparing the measurement signal to each of a plurality of templates, wherein each template in the plurality of templates is associated with a different possible velocity of the fluid. 
 
     
     
         17 . The method of  claim 11  wherein (b) comprises:
 interpolating at least one of the measurement signal and the template. 
 
     
     
         18 . The method of  claim 11  further comprising:
 transmitting a representation of the estimated velocity or the measurement signal to a server. 
 
     
     
         19 . A method of installing a fluid flow meter, the fluid flow meter comprising a sensor to measure a velocity of a fluid flowing through a lumen and to provide a measurement signal representative of the velocity, a memory to store a template associated with a possible velocity of the fluid, and a processor, communicatively coupled to the sensor and to the memory, to perform a comparison of the measurement signal to the template and to estimate the velocity based on the comparison, the method comprising:
 securing the fluid flow meter to an exterior of a structure that defines the lumen.   
     
     
         20 . The method of  claim 19  further comprising:
 setting the velocity to a known value; 
 generating an estimated velocity with fluid flow meter; and 
 calibrating the fluid flow meter based on the known value and the estimated velocity. 
 
     
     
         21 . The method of  claim 20  further comprising:
 generating an estimated diameter of the lumen based on the known value and the estimated velocity. 
 
     
     
         22 . The method of  claim 20  further comprising:
 verifying the diameter of the lumen based the estimated diameter and a description of the lumen or the structure.