The document explains data acquisition (DAQ), detailing the conversion of physical parameters into digital data using sensors, signal conditioners, hardware, and software. It highlights the digitization process, its importance in modern technology, and discusses the Modbus communication protocol and its various types. Additionally, it covers the architecture of DAQ systems, communication standards, and technical specifications relevant to Modbus operations and wiring configurations.

1. DATA ACQUISITION
AND
SOFT COMMUNICATION

2. What is Data Acquisition ?
Manual Process of Data Acquisition
Technician operator checking and record
reading value of pressure, temperature and
flow transmitter in daily log book

3. What is Digitization?
 Digitization refers to the process of converting physical objects into
digital format. An example of this would be document scanning,
where text from physical paper is converted into PDF or other digital
formats, which are then stored in the computer
 Digitization’s purpose is to encode information in computers by
converting from analog to digital format. The process mainly deals with
recording data that can eventually be used in digital technologies.
 This process of digitizing the reality of the world around us has a
name: Data acquisition or, shorter, DAQ. Thanks to this procedure,
information can be displayed, analyzed and stored on a computer
and used to make better decisions that benefit the business.

4. How does Data Acquisition System work?
 A data acquisition system (DAS) is a device used to
convert physical parameters into digital data that can
be read by a computer.
 Temperature, light intensity, vibration, gas pressure, fluid
movement, and force are a few examples of factors
often considered in a DAQ system
 The basic scheme of DAS is illustrated in Following Fig.

5. Components Of DAQ :  Sensors
 Signal
Conditioners
 Hardware
 Software

6. Function of DAQ Components
 Sensors : Sensors are devices that
convert physical parameters into
electrical signals that can be measured
and recorded. They are used to
measure physical parameters such as
temperature, pressure, flow, and level

7. Function of DAQ Components
 Signal Conditioners : Signal conditioners amplify, filter, and convert the
sensor signals into a form that can be read by the data acquisition
hardware.

8. Function of DAQ Components
 Hardware: Data acquisition hardware is the hardware that is connected
between the sensors and the computer. This hardware is either connected
to the computer employing a USB port or ethernet port. This component of
the DAQ system serves to convert analog signals into digital signals. This
component is at the core of all data acquisition systems.

9. Function of DAQ Components
 Software: DAQ software provides a user interface for configuring and
controlling the data acquisition devices, as well as for viewing and
analyzing the data that has been acquired. Specialized data
acquisition software required for acquiring, storing, and processing data
in a logical format is available

10. DAQ Place in Automation Pyramid

11. System Architecture for Data Acquisition
Data Acquisition
Hardware
RTD
Signal
Conditionner Resistance
Input
Data Acquisition
Software
RS 485 to USB
Convertor
4-20 mA
Output
Sensor
Temperature
Transmitter
RS 485 Soft
Communication
Modbus RTU
Protocol

12. System Architecture for Data Acquisition

13. System Architecture for Data Acquisition

14. Communication Protocol
1. HART (Highway Addressable Remote Transducer)
2.Modbus
3. PROFIBUS (Process Field Bus)
4. PROFINET (Process Field Net)
5. EtherNet/IP (Ethernet Industrial Protocol)
6. Foundation Fieldbus
7. OPC (OLE for Process Control)
8. DeviceNet
9. CANopen
10.Industrial Ethernet
11.AS-Interface (Actuator Sensor Interface)
12.Zigbee
13.MQTT (Message Queuing Telemetry Transport)
14.Bluetooth
15.Wi-Fi

15. What is Modbus ?
 MODBUS is a communication protocol developed by Modicon in 1979 (now
Schneider Electric) used by programmable logic controllers. Modbus transmission of
data can be over serial lines or ethernet. Many devices are now Modbus compliant
since it's now a widely accepted communication protocol.
Supervisory Control and Data Acquisition mainly use Modbus (SCADA) to receive
data from remote terminal units (RTU) and PLCs.
 Modbus is an open protocol, meaning that it's free for manufacturers to build into
their equipment without having to pay royalties. It has become a very common
protocol used widely by many manufacturers throughout many industries. Modbus is
typically used to transmit signals from instrumentation and control devices back to a
main controller or data gathering system.
 Modbus communication types
 Modbus can be grouped into three broad types:
1. Modbus RTU – Serial
2. Modbus ASCII - Serial
3. Modbus TCP – Parallel Ethernet

16. Modbus RTU Working
 Modbus is transmitted over serial lines between devices. The simplest setup would be
a single serial cable connecting the serial ports on two or more devices, a Master
and Slaves.
 The data is sent as series of ones and zeroes called bits. Each bit is sent as a voltage.
Zeroes are sent as positive voltages and a ones as negative. The bits are sent very
quickly. A typical transmission speed is 9600 baud (bits per second).
 A Modbus RTU operates a Master to slave structure. A Modbus master can connect
with up to 32 slaves and exchange data. Each slave has its own 8-bit device address,
often known as a unit number or Device ID Number or Sr.Number.

17. Modbus RTU Working
 The address of the slave for whom the communication is intended is included in the
packets transmitted by the master. The slave must only answer if its address is
recognized, and it must do so within a specific amount of time, or the master will
consider it a "no response" error

18. Modbus RTU Working
 A slave is any peripheral device that analyzes data and delivers a response message
to the master using Modbus, such as an I/O transducer, valve, network drive, or other
measuring devices. The communication media for an RTU network is serial, either
using RS232, RS422, or RS485.
 Modbus Protocol | Physical connection of RS232, RS485, RS422 using a DB9 cable

19. Modbus Register addressing
 The Modbus protocol is based on the concept that Modbus slaves hold their data in a
series of defined status flags and registers, with defined addresses. A number of flags
and registers are set aside for a number of purposes:
 Discrete Outputs (Coils) – Digital Output
 Discrete inputs (contacts) – Digital Input
 Input registers – Analog Input Holding Registers
 Holding registers – Analog Output Holding Register

20. Modbus Register addressing
1. Discrete Outputs (Coils): Coils are one-bit registers used as outputs. They are both
read and write registers
2. Discrete inputs (contacts): Discrete inputs are bit contact registers, and they can
only be read. They can best be described as the contacts in PLC programming.
3. Input registers: Inputs registers are 16-bit registers used for inputs. They are read only
4. Holding registers: Holding registers are 16-bit registers that are both read and write.
They are the most universal register as they can be used for inputs, outputs, and for
holding any kind of data.

21. RS 485- Daisy Chain Wiring
Each device [MASTER or SLAVE] has a connection port with 2 terminals that are used to
communicate with that particular device over MODBUS RTU – RS485. These terminals are
mostly marked as A [or DATA +] and B [or DATA -]. The cabling is done such that all these
devices are connected in parallel. This means that all the A terminals should be connected
together and all the B terminals should be connected together

22. RS 485- Setting Communication Parameter
Baud rate Set this parameter based on the baud rate of the
connected device.
The value can be 1200, 2400, 4800, 9600, 19200,
or 115200.
Parity Set this parameter based on the parity mode of the
connected device.
The value can be None, Odd parity, or Even parity.
Stop Bit Set this parameter based on the stop bit of the
connected device.
The value can be 1 or 2.

23. RS 485- Modscan / Modbus Tester
 Software Tools to check the communication

24. Thank You