MSP430FW42X Non-Magnetic Sensor Water Meter Solution

火辣西米秀

MSP430FW42X Non-Magnetic Sensor Water Meter Solution [Copy link]

The MSP30FW42X non-magnetic sensor water meter has the characteristics of low power consumption (quiescent current is less than 4 microamperes), wide flow measurement range, high accuracy, good stability and consistency. It maintains high measurement accuracy especially at small flow rates. At the same time, it is not affected by various types of water rust and impurities. It is particularly suitable for long-term use in heating environments with poor water quality without affecting the measurement accuracy.

　　1. Main performance of single chip microcomputer

　　The MSP430FW42X series of microcontrollers is TI's latest dedicated MCU chip developed for electronic flow and rotary motion detection. It perfectly combines an ultra-low power MCU, a rotary scan interface (Scan IF) and a liquid crystal display LCD driver module. The device's ultra-low power structure and flow detection module not only extend the battery life, but also improve the accuracy and performance of the instrument.

　　In addition to being fully compatible with existing MSP 430F 41x products, the MSP430FW42X also has the following key features:

　　Scan IF units for flow measurement in water, heat and gas meters;

　　Integrated LCD driver with up to 96 segments;

　　Power-off protection function and supply voltage monitor;

　　Two multi-channel PWM timers;

　　Universal analog comparator_A that can realize analog-to-digital conversion.

　　2. System composition

　　The water meter and heat meter developed using MSP430FW42X directly use the internal flow scanning module (Scan IF) and do not require an external flow detection IC, directly replacing TMS3723B, greatly simplifying the system hardware design and software design, and improving the stability of the system. The block diagram of the non-magnetic water meter system developed using MSP430FW42X is as follows:

　　Figure 1 System block diagram

　　Figure 2 Actual photo

　　3. Measurement Principle

　　This solution detects fluid flow by converting fluid flow into rotational motion. This conversion is achieved by using an impeller with a metal film. The fluid in the pipeline drives the impeller to rotate continuously, and its speed is directly determined by the flow rate of the fluid. This mechanical rotation signal is converted into an electrical signal by a non-magnetic non-contact sensor and sent to the SCAN IF module of the microcontroller. The SCAN IF module calculates the rotation (fluid flow) and its direction.

　　4. SCAN IF Module Introduction

　　The SCAN IF module can automatically detect linear or rotational motion at low power consumption. The SCAN IF module consists of three parts: analog front end (AFE), signal processing state machine (PSM), and timing state machine (TSM). The main components of the analog front end are a "VCC/2" generator, a comparator, and a 10-bit DAC. The analog front end is used to excite the sensor, detect the signal level and convert the signal into digital form; these digital signals enter the signal processing state machine, which calculates the rotation (fluid flow) and its direction; the timing state machine is used to control the analog front end and the signal processing state machine.

　　Figure 3 SCAN IF module block diagram

　　5. Main functions

　　1. Water consumption measurement

　　Total water consumption and monthly water consumption measurement;

　　Store the historical water consumption of the last 12 months;

　　2. Time Management

　　With calendar, timing and leap year automatic switching functions;

　　The calendar and time settings have measures to prevent unauthorized persons from operating;

　　3. Event Record

　　Water volume record

　　The time and amount of last water purchase, total water consumption, remaining water, and historical water consumption in the last 12 months

　　Battery Management

　　Battery low voltage record and prompt

　　Destruction of records

　　Meter removal record

　　4. Display

　　Display the water meter's accumulated flow, remaining water volume, current water purchase volume, water meter valve status, battery status and other related information;

　　The display order and display interval can be preset;

　　Alarm and error message prompts;

　　5. Communication interface

　　You can choose one of the following three methods.

　　IC Card

　　RFID Card

　　M_BUS Teletransmission

　　6. Button operation

　　Display buttons can be set according to the user's base meter and case.