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Which type of modulation is used in hart communication?

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Question added by Muhammad Umar Umar , I& C Engineer , Pakistan Refinery Limited Karachi, Pakistan
Date Posted: 2016/12/14
ASSAD ULLAH KHAN
by ASSAD ULLAH KHAN , Manager , Instrumentation Limited

FSK Frequency Shift keying in which a digital signal is superimposed on analogue signal

wael moustafa elmetwally hamada hamada
by wael moustafa elmetwally hamada hamada , مساند مناقصات حكومية لاجهزة المكتبية+ , بيت الرياض- مجموعة الجريسي

The primary form of communication used in analog transmitters is a current loop with a normal range of 4 mA to 20 mA, employing a transmitter, a receiver, and a power supply. It enables features such as remote calibration, fault interrogation, and transmission of process variable data. Low-power transmitters and receivers must operate on the minimum current, 4 mA or less, depending upon the “headroom” required for error indication. These current loops are reliable, robust, and highly immune to environmental interference over long communication distances. A significant disadvantage, however, is that a single loop allows only one-way communication from a sensor, or to an actuator, and can only transmit one process variable.

The introduction of the HART standard provided a means to create “smart” transmitters, by adding digital communication capability, sharing the same twisted-pair line used for traditional 4-mA-to-20-mA instrumentation. A 4-mA-to-20-mA analog current is modulated by a 1-mA peak-to-peak FSK signal—without interrupting the original primary variable transmission—while still leaving headroom for operating the loop. The HART protocol has become the global standard for sending and receiving digital information over analog wires between smart devices and a control or monitoring system

mohamed nasar abdullah
by mohamed nasar abdullah , Maintenance team leader , aujan cocacola industries co

operates using the

it is working by frequency shift keying(FSK) principle. The digital signal is made up of two frequencies1,200 Hz and 2,200 Hz representing bits 1 and 0, respectively. Sine waves of these two frequencies are superimposed on the direct current (dc) analog signal cables to provide simultaneous analog and digital communications Because the average value of the FSK signal is always zero, the 4–20 mA analog signal is not affected. The digital communication signal has a response time of approximately 2–3 data updates per second without interrupting the analog signal. A minimum loop impedance of 230 Ω isrequired for communication.

DADI Nooka RAJU
by DADI Nooka RAJU , Instrumentation Engineer , Zerock Construction Nigerian Company

Yokogawa and Invensys Foxboro and Emerson Rosemount RS3 system and Siemens, S-5, S-7 control system.

Ahmed Helmi Abdel Wahab
by Ahmed Helmi Abdel Wahab , Automatic Control & Instrumentation Engineer , Suez Oil Processing Company "SOPC"

Frequancy shift key (FSK) signal to establish digital communication over the 4-20mA analog signal. 

ahmed ali
by ahmed ali , Instrumentation engineer , Egyptian Projects Operation & Maintenance (EPROM)

HART uses FSK modulation techniques frequancy shift key

RAVINDRA PATLE SONALU PATLE
by RAVINDRA PATLE SONALU PATLE , JUNIOR MANAGER INSTRUMENT AND ELECTRICAL , JSW STEEL LTD DOLVI WORKS (MUMBAI)

This enables two-way field communication to take place and makes it possible for additional information beyond just the normal process variable to be communicated to/from a smart field instrument. The HART Protocol communicates at 1200 bps without interrupting the 4-20mA signal and allows a host application (master) to get two or more digital updates per second from a smart field device. As the digital FSK signal is phase continuous, there is no interference with the 4-20mA signal.

REJI JOY THOPPIL
by REJI JOY THOPPIL , Technical Consultant/ Technical Director , Technopano

The HART Devices ( Highway Addressable Remote Transmitter ) uses a frequency Shift keying digital communication which is superimposed over an analog signal. The signal uses two frequencies which corresponds to a  '0' and '1' digital data bits and the data is transmitted at a speed of 1200 bps. 

Mohamed Bayoumy
by Mohamed Bayoumy , Projects Engineer , Kharafi National

Frequency Shift Keying (FSK)

WAQAS ABBASI
by WAQAS ABBASI , Sr Instrument Officer , Attock Refinery Limited

HART  is an acronym for Highway Addressable Remote Transducer. The HART Protocol makes use of the Bell 202 Frequency Shift Keying (FSK) standard to superimpose digital communication signals at a low level on top of the 4-20mA.

The HART Communication Protocol (Highway Addressable Remote Transducer) is a hybrid analog+digital industrial automation protocol. Its most notable advantage is that it can communicate over legacy 4-20 mA analog instrumentation current loops, sharing the pair of wires used by the analog only host systems.

Mostafa mohamed El Maghraby  PMP
by Mostafa mohamed El Maghraby PMP , instrumentation General Manager , abu qir fertilizer and petrochemical ind.

used in analog transmitters is a current loop with a normal range of 4 mA to 20 mA, employing a transmitter, a receiver, and a power supply. It enables features such as remote calibration .FSK Frequency Shift keying in which a digital signal is superimposed on analogue signal

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