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Low Power Method for Flow Meters

IP.com Disclosure Number: IPCOM000244492D
Publication Date: 2015-Dec-16
Document File: 5 page(s) / 272K

Publishing Venue

The IP.com Prior Art Database

Abstract

Flow meters that operate in battery supply environments need to consume as little power as possible that allow it to function properly so that high energy efficiency is achieved. However, in real situations, flow meters always sample the sensors at full speed, which consumes a lot of redundant power, and in residential user cases the meters are in static state with or without little flow for most of the day. We propose a method to save power when flow meters have no flow or little flow by using dynamic sampling rate automatically.

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Low Power Method for Flow Meters

ABSTRACT

Flow meters that operate in battery supply environments need to consume as little power as possible that allow it to function properly so that high energy efficiency is achieved.  However, in real situations, flow meters always sample the sensors at full speed, which consumes a lot of redundant power, and in residential user cases the meters are in static state with or without little flow for most of the day.  We propose a method to save power when flow meters have no flow or little flow by using dynamic sampling rate automatically.

KEYWORDS

Flow meters, low power, sample rate, adaptive

1.     INTRODUCTION

In common residential flow meters, each time the meters sample, all sensors are turned on, all comparators are turned on, and all counters are enabled.  These components consume a lot of power for battery supplied environments.  Figure-1 illustrates a water meter flow using such a sampling method.

Figure-1

According to Nyquist criteria, each coding paddle sector should be sampled at least twice to ensure no data is missed.  In older design flow meters, the sample rate is always at max speed.  Assume flow meter max rotation is 20 rps, the sampling rate should be 2 x 20 x 8 (8 sectors per rotation) = 320 Hz, period is 3.125ms, and if we assume each sample consumes 1 unit power, older flow meters consume 320 units power per second, and 320*60*60*24 ≈ 2.8e+7 unit power for 24 hours each day;

Figure-1-1 Old flow meter sample flow

2.     WHAT IS THE MOTIVATION?

Our method is to use one kind of dynamic flow (shown in Figure 2) that reduces the sampling rate to a proper value in order to reduce total power consumption for flow meters used in, for example, residential water meters.

Normal residential users only use water for about 1 hours with max flow per day in average, nearly 23 hours of a day are in idle for meters; Set minimum sample period to “ Ts ”; Set missed 8 sectors rotation state at max speed after Ts time; Then Ts = 1/20 = 50ms (missed < 8 sectors at most for a Ts time is acceptable); Leave 10% margin, Ts = 45ms, acceptable minimum sample speed is about 7% of maximum sample speed, total power consumption of 24 hours reduced to about 11% of the old flow meter user case as shown in Figure-3 (STEPmin’s value depends on how the sample rate decline curve meet with actual user cases to consume least power).

Our proposed flow meter sample flow for low power is described as below:...