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Maxim公司的MAX35101是内置了放大器和比较器的时间/数字转换器,是超声波热量(流量)表完整的模拟前(AFE)解决方案.时间/数字转换精度20ps,测量范围高达8ms,单电源2.3V-3.6V工作,主要用在超声波热量表,超声波水表和超声波气表.本文介绍了MAX35101主要特性和优势,框图,应用电路,以及MAXREFDES70#超声波流量表主要特性,框图,电路图,材料清单和PCB元件布局图.
The MAX35101 is a time-to-digital converter with built-in amplifier and comparator targeted as a complete analog front-end (AFE) solution for the ultrasonic heat meter and flow meter markets.
With a time measurement accuracy of 20ps and auto-matic differential time-of-flight (TOF) measurement, this device makes for simplified computation of liquid flow. Early edge detection ensures measurements are made with consistent wave patterns to greatly improve accuracy and eliminate erroneous measurements.
Multihit capability with stop-enable windowing allows the device to be fine-tuned for the application. Internal analog switches, an autozero amplifier/comparator, real-time clock (RTC), and programmable receiver sensitivity provide the analog interface and control for a minimal electrical bill of material solution. The RTC provides an event timing mode that is configurable and runs cyclic algorithms to minimize microprocessor interactivity and increase battery life.
Built-in arithmetic logic unit provides TOF difference mea-surements. A programmable receiver hit accumulator can be utilized to minimize the host microprocessor access and thus minimize current consumption.
For temperature measurement, the MAX35101 supports up to four (4) 2-wire PT1000/500 platinum resistive tem-perature detectors (RTD).
A simple 4-wire SPI interface allows any microcon-troller to effectively configure the device for its intended measurement.
On-board 8KB user flash allows the MAX35101 to be nonvolatile-configurable and provide nonvolatile energy use data to be logged. Configuration can be recalled any-time with a SPI command.
MAX35101主要特性和优势:
Early Edge Detect Ultrasonic Time-of-Flight
? Time-to-Digital Accuracy Down to 20ps
? Measurement Range Up to 8ms
? Multihit Capability
? Early Edge Detect to Provide Advanced Accuracy
? Programmable TOF Hit Accumulator
? Two Channels: Single-Stop Channel
? Stop-Enable Windowing with Edge Trigger Select
? Built-In Pulse Launcher with Programmable Frequency
? Autozero Receiver Comparator
? Programmable Acoustic Recovery Sensitivity
? Automatic Two-Pulse Algorithm for Differential TOF Measurement
Temperature Measurement
? Up to Four (4) 2-Wire Sensors
? PT1000 and PT500 RTD Support
Event Timing Mode
? Allows Automatic Measurement Cycles
? Minimizes Microcontroller Interactivity to Reduce Power Consumption
Tamper Detection
? Single Input Pin Detects Tamper and Generates Processor Interrupt
Power Consumption
? 2.3V to 3.6V Single-Supply Operation
General
? 8KB of Nonvolatile Flash Memory for Data Logging
? Built-in Real Time Clock for Time of Day Monitoring
? 4MHz Oscillator Can Be a Ceramic Device to Lower System Cost
? Small, 5mm x 5mm, 32-Pin TQFP Package
? 4-Wire SPI Interface
? -40℃ to +85℃ Operation
MAX35101应用:
Ultrasonic Heat Meters
Ultrasonic Water Meters
Ultrasonic Gas Meters
图1. MAX35101框图
图2. MAX35101典型应用电路图
MAXREFDES70#超声波流量表
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 years.1The 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.
图3. MAXREFDES70#超声波流量表外形图
图4. MAXREFDES70#超声波流量表系统框图
MAXREFDES70#超声波流量表主要特性:
High precision
Large flow rate range
Ultra-low power consumption (20 years of battery life)
Compact and low cost
MAXREFDES70#超声波流量表应用:
Ultrasonic heat meters
Ultrasonic cooling meters
Ultrasonic flow meters
图5. MAXREFDES70#超声波流量表电路图
MAXREFDES70#超声波流量表材料清单:
图6. MAXREFDES70#超声波流量表PCB元件布局图:顶层
图7. MAXREFDES70#超声波流量表PCB元件布局图:底层
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