ADI Electromagnetic Flow Meter Solutions System Theory and Typical Architecture of Industrial Electromagnetic Flow Meters COIL TRANSDUCER The operating principle of the electromagnetic flow meter is based on Faraday’s law of electromagnetic induction. When the magnetic field direction perpendicular to the conductor cutting magnetic line is speed V, both ends of the conductor will be induced by a certain force E, and the liquid flow rate change can be calculated by detecting the value of the force. D ELECTRODE The features of electromagnetic flow meters are no pressure loss and no impact from viscosity, fluid density, temperature, pressure, or conductivity, making it suitable for measuring pulp, slurry, and sewage with high accuracy. VELOCITY (V) EMF (E) MAGNETIC FLEX DENSITY (B) An electromagnetic flow meter system consists of power supplies, magnetic excitation, signal conditioning, analog-to-digital conversion, processor, display, keyboards, logic I/Os, and multiple communications like 4 mA to 20 mA, HART, Profibus, RS-485/RS-422/RS-232, Modbus, and Foundation. E=K×B×V×D K is instrument constant B is magnetic flex density V is average fluid velocity across the pipe D is diameter of measurement pipe System Design Considerations and Major Challenges of Industrial Electromagnetic Flow Meters To appropriately design an electromagnetic flow meter system, designers must consider many different system requirements, including accuracy, bandwidth, and magnetic excitation frequency. • Electromagnetic flow meter sensor output ranges can be as small as several tens of μV with a certain common voltage. The output impedance is often higher than the MΩ range. The front-end precision operational amplifier or instrumentation amplifier requires ultrahigh input impedance, very low leakage current, and excellent CMRR. • Electromagnetic flow meter product maximum measurement range can be as wide as 1500:1, and the range for corresponding flow rate is 0.01 m/s to 15 m/s. • Measurement accuracy can be as high as 0.2% of reading, which often requires a 16-bit to 24-bit analog-to-digital converter. • Connectivity to different fieldbus protocols, such as HART, Profibus, Modbus, Foundation, RS-485/RS-422/RS-232, and wireless HART. • Isolation needed between system power supply, central logic unit, communication, and I/Os. Isolation grade varies from 1 kV to 2.5 kV. • Portable electromagnetic flow meters require ultralow power MCU, amp, and ADC components. • Higher frequency square wave excitation improves the flow of mud and noise immunity, but needs to be balanced with zero stability. Industrial site temperature environments are quite complex and sometimes even extremely adverse. Low temperature drift coefficient and low power consumption are very important for electromagnetic flow meters to withstand a wide working temperature range. ADI offers a complete portfolio such as precision amplifiers, precision references, precision analog-to-digital converters, and ARM core microprocessors. Also, EMC interference immunity, such as for ESD, EFT and surge, is a big challenge for electromagnetic flow meters. The high level ESD immunity components offered by ADI greatly help to improve its reliability and robustness. In addition, the limited space inside electromagnetic flow meters requires dense systems. Therefore, the form factor has to be reduced to accommodate this. Recently, advances in integration have allowed system designers to migrate to smaller, lower power, lower cost solutions, with performance approaching that of larger systems. The challenge moving forward is to continue to drive the integration of these solutions while increasing their performance and diagnostic capabilities. ADI offers market tailored solutions to aid in the design process. These solutions feature our industry-leading technologies and offer a range of design options: from implementation of discrete components to fully integrated solutions and everything in between. Total Solutions from ADI Leverage ADI amplifier, data conversion, signal processing, communications, and power technology and expertise to design high resolution, low noise industrial electromagnetic flow meter systems. www.analog.com Main Signal Chain AC-TO-DC 110V/220V AC-TO-DC ANALOG PROCESS POWER EXCITATION POWER COMM POWER DC-TO-DC INTERFACES WIRELESS RS-485/ RS-422 LDO ISOLATED DC-TO-DC GATE DRIVER PROFIBUS REF I/O iCOUPLER ISOLATION EMF SIGNAL AMP MUX MAIN ADC AMP OPTIONAL AUX AMP ADC PROCESSOR MCU isoPOWER ISOLATION HMI DAC 4mA TO 20mA KEYBOARDS DISPLAY TEMPERATURE MEASURE Note: The signal chain above is representative of a typical EM flow meter system. The technical requirements of the blocks vary, but the products listed in the table are representative ADI's solutions that meet some of those requirement. Main Product Introduction Part Number Description Key Features Benefits ADC AD7663 16-bit, 250 kSPS CMOS ADC 35 mW @ 5 V, 16-bit no missing code, INL = 3 LSB, S/(N + D): 90 dB type @ 100 kHz Fast throughput, serial or parallel interface AD7685 16-bit, 250 kSPS PulSAR ® ADC 16-bit 250 kSPS no missing code, INL = ±2 LSB max, 4 mW @ 5 V/100 kSPS Low power, internal conversion clock, high throughput rate AD7682 16-bit, 4-channels, 250 kSPS, PulSAR ADC 16-bit 250 kSPS no missing code, INL = ±1.5 LSB max, 12.5 mW @ 5 V/250 kSPS Unipolar single-ended and differential, low power, single power with bipolar input, competitive price AD7192 24-bit 2 differential/4 pseudo channels, Σ-Δ ADC with PGA 4.8 kHz, ultralow noise, rms noise: 11 nV @ 4.7 Hz (gain = 128), 15.5 noise-free bits @ 2.4 kHz (gain = 128), differential inputs Ultralow noise, internal PGA, high precision Σ-Δ ADC 4.7 Hz to 470 Hz, embedded 2 switchable current sources, reference, PGA, low noise Low power consumption and designed for RTD/thermocouple temperature measure Main ADC/Aux ADC 16-bit to 24-bit, 3 differential AD7792/AD7793/ to 6 differential channels, AD7794/AD7795 Σ-Δ ADC with PGA Processor/MCU ADUC7060 Analog microcontroller (ARM7TDMI core) 24-bit, 8 kSPS Σ-Δ ADC up to 10 ADC channels; 1-channel 14-bit voltage High resolution, low power, and abundant DAC outputs; 16-bit, 6-channel PWM; on-chip voltage reference, resources ±10 ppm/°C and temperature sensor; programmable sensor excitation current sources, 200 µA to 2 mA; up to 14 GPIO pins 2 | ADI Electromagnetic Flow Meter Solutions Main Product Introduction (continued) Part Number Description Key Features Benefits AMP AD8622 Low power and precision op amp Bandwidth = 540 kHz; VNOISE density= 11 nV/√Hz; I B = 45 pA; I SY = 350 μA Very low noise and low leakage current AD8667 Low noise op amp Bandwidth = 520 kHz; VNOISE density = 21 nV/√Hz; I B = 0.3 pA; I SY = 355 μA Extremely low leakage current, battery powered ADA4051-1 Micropower and auto-zero op amp Bandwidth = 125 kHz; VNOISE density = 95 nV/√Hz; I B = 20 pA; I SY = 20 μA Perfect buffer for battery supply, competitive price AD8220 Instrumentation amplifier Bandwidth = 1.5 MHz; VOS = 1 mV; VNOISE density = 90 nV/√Hz; I B = 25 pA; gain control interface = resistor New generation for replacing classic AD620 AD8226 Instrumentation amplifier Bandwidth = 1.5 MHz; VOS = 1.2 mV; VNOISE density = 2 μV/√Hz; I B = 27 nA; gain control interface = resistor Good performance and competitive price AD8228 Instrumentation amplifier Bandwidth = 650 kHz; VOS = 50 μV; VNOISE density = 15 nV/√Hz; I B = 600 pA; gain control interface = pin strap Excellent temperature drift and low noise AD8231 Instrumentation amplifier Bandwidth = 2.7 MHz; VOS = 15 μV; VNOISE density = 66 nV/√Hz; I B = 500 pA; gain control interface = digital Digital gain control with low offset voltage AD8276 Difference amplifier Wide input range beyond supplies; bandwidth: 550 kHz; low offset voltage drift: ±2 μV/°C maximum; low gain drift: 1 ppm/°C maximum Low cost solution for current source and RTD measurement Current source DAC 12-bit/16-bit resolution; 0 mA to 24 mA ±0.01% FSR TUE; ±3 ppm/°C typical output drift; on-chip reference (10 ppm/°C maximum) Universal output DAC, supports HART communication AD5421 Current source DAC 16-bit resolution; 3.2 mA to 24 mA; NAMUR-compliant alarm; TUE error: 0.05% maximum; on-chip reference TC: 4 ppm/°C maximum, loop voltage range: 5.5 V to 52 V Loop powered universal output DAC, supports HART AD5660 nanoDAC ® Single 16-bit, 5 ppm/°C on-chip reference; tiny 8-lead SOT-23/MSOP packages Tiny package and high performance DAC AD5410/ AD5420 REF Sink low quiescent current: 100 μA (maximum), low dropout voltage ADR34xx Voltage references Initial accuracy: ±0.1% (maximum) maximum temperature coefficient: 8 ppm/°C ADR44x Voltage references Initial accuracy: ±0.04% (maximum), temperature coefficient: 3 ppm/°C; voltage noise: 2.25 μV p-p type in 0.1 Hz to 10 Hz Ultralow noise, high initial accuracy, and perfect temp drift ADuM322x Isolated gate driver Dual-channel isolated, 2.5 kV rms; 4 A peak output current, 4.5 V to 18 V output drive, output shoot-through logic protection; dc to 1 MHz Output shoot-through logic protection, enhanced system-level ESD performance ADuM7234 Isolated gate driver Dual-channel isolated, 1 kV rms; 4 A peak output current, high frequency operation: 1 MHz maximum, narrow-body, 16-lead SOIC, 1 kV rms input-to-output withstand voltage 1 kV rms input-to-output withstand voltage with competitive price ADuM320x Dual channel Digital isolators 2.5 kV rms; low power operation, 3 V/5 V level translation; high data rate: dc to 25 Mbps (NRZ) enhanced system-level ESD performance per IEC 61000-4-x Dual dc-to-25 Mbps (NRZ) signal isolation channels, low power operation ADuM140x Quad channel digital isolators 2.5 kV rms; low power operation, 3 V/5 V level translation; high data rate: dc to 90 Mbps (NRZ), output enable function High data rate: dc to 90 Mbps (NRZ), low power operation ADuM744x Quad channel digital isolators 1 kV rms isolation rating, low power operation; bidirectional communication, up to 25 Mbps Low power operation and competitive price data rate (NRZ),3 V/5 V level translation ADM2587E Isolated RS-485/ RS-422 Half or full duplex, 500 kbps, 5 V or 3.3 V operation Integrated isolated dc-to-dc ±15 kV ESD ADM2483 Isolated RS-485 transceiver Half-duplex, 500 kbps data rate, 5 V or 3 V operations (VDD1), low power operation: 2.5 mA max, 2.5 kV isolation Low power operation and competitive price ISM band FSK/GFSK/OOK/ MSK/GMSK transceiver IC Frequency bands: 862 MHz to 928 MHz, 431 MHz to 464 MHz; ultralow power; ISM band, data rates supported, 1 kbps to 300 Kbps, single-ended and differential PAs ISM band, data rate: 1 kbps to 300 kbps, very low power consumption ADG1408 Multiplexers 4-channel/8-channel, ±15 V supply; 4.7 Ω maximum on resistance, up to 190 mA continuous current, rail-to-rail operation Fully specified at ±15 V/+12 V/±5 V ADG5408 Multiplexers Latch-up proof construction, 4-channel/8-channel; 8 kV ESD rating, low on resistance (13.5 Ω typical), Fully specified at ±15 V, ±20 V, +12 V, and +36 V, high switching speed, break-beforemake switching action Gate Driver Isolator Interface Wireless ADF7023 MUX www.analog.com | 3 Main Product Introduction (continued) Part Number Power ADP2300/ ADP2301 Description Key Features Benefits DC-to-DC regulator Single nonsynchronous step-down dc-to-dc converter, 1.2 A output, 0.7 MHz/1.4 MHz frequency, input voltage range from 3.0 V to 20 V Small SOT23-6 package, few peripheral components, and small solution size ADP1720 Linear regulator Wide input voltage range: 4 V to 28 V, max output current: 50 mA, accuracy over line, load, and temperature: ±2%, fixed 3.3 V and 5.0 V output voltage options Wide input voltage range: 4 V to 28 V ADP1612/ ADP1613 DC-to-DC regulator Voltage input: 1.8 V to 5.5 V, output voltage: VIN to 20 V. pin-selectable 650 kHz or 1.3 MHz PWM frequency Boost dc-to-dc ADP125 Linear regulator 5.5 V input, 500 mA maximum output current, 1% initial accuracy, up to 31 fixed-output voltage options available from 1.75 V to 3.3 V; low quiescent current: 45 µA Excellent load/line transient response Circuits from the Lab™ Reference Circuits for Electromagnetic Flow Meter Solutions • Complete High Speed, High CMRR Precision Analog Front End for Process Control (CN0213)—www.analog.com/CN0213 • 4 mA-to-20 mA Loop-Powered Temperature Monitor Using the ADuC7060/ADuC7061 Precision Analog Microcontroller (CN0145)—www.analog.com/CN0145 • Simplified 16-Bit, 4 mA-to-20 mA Output Solution Using the AD5420 (CN0098)—www.analog.com/CN0098 • 16-Bit Fully Isolated Output Module Using the AD5422 Single Chip Voltage and Current Output DAC and the ADuM1401 Digital Isolator (CN0065)— www.analog.com/CN0065 • Fully Isolated Input Module Based on the AD7793 24-Bit Σ -Δ ADC and the ADuM5401 Digital Isolator (CN0066)—www.analog.com/CN0066 What ADI Can Provide to Customers • ADC ADIsimADC; Σ-Δ ADC register configuration assistant • DAC ADIsimDAC • AMP ADIsimOpAmp, ADIsimDiffAmp • Power EVB and ADIsimPower • Processor EVB emulation tools and some software Customer Interaction Center [email protected] EngineerZone ez.analog.com Free Sample www.analog.com/sample ©2011 Analog Devices, Inc. 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