Programming Analog Inputs 4-20mA PLC Logo!

The Analog Inputs are values of parameters mainly Electrical Signals that work with the PLC and are Outputs from Sensors (Transmitters) by Current (0-20mA/4-20mA) or by Volts (0-10V), this value is Scaled in PLC Software and then we have a Real Value very similar to Sensor Value

OFF => 0% => 4mA

Simulating in PLC a Signal 4-20mA becoming in 0-1000/0-100

First, We must to know these concepts:

Input/Output AI in (mA): There are the Analog Signals working in Current, mainly 4-20mA or 0-20mA, is one of the most used signals in the industry (have advantanges) between Sensors/Transmitters and PLCs or other devices capable to work with 4-20mA

Input/Output AI in (Volts): There are the Analog Signals working in Voltaje, mainly 0-10V, The Voltage in Analog Signals is most used in Outputs, it's because we have more Actuators using 0-10V as Valves, Servomotors, Motors 0-10V, etc

Sensors / Transmitters: There are the electronic devices that mainly measure all types of parameteres (Flow, Pressure, Temperature, etc) and are configured to send a signal to PLC by 0-20/4-20mA or 0-10V, the values allowed in that a PLC can read, Scale signals are developed in Software

Must Knowledge

Computation
Electricity
First Time with Logo!

MAIN SUMMARY
STEP 1: Necessary Elements
STEP 2: Analog Inputs Types
STEP 3: Hardware You Must have for AI
STEP 4: Wiring and Technical Details
STEP 5: Programming in PLC (VIDEO)
STEP 6: Upload Program to Logo!
STEP 7: QUESTIONS & ANSWERS

STEP 1 : NECESSARY ELEMENTS

First Remember have all elements to use Hardware and Software

The Programmable Relay PLC Logo! need a Software to make the Program that control all our process, so we need these elemments:

Notebook or Portable Computer with CD-USB o CD
PLC Logo! V8 Siemens
Communication Cable Ethernet Cat5e o higher
Software PLC Logo Siemens; Logo Soft Comfort V8.0 or higher
Wiring in 220VAC (We use Logo! 220VAC)

NO problem if we dont have the Original CD, we can Download DEMO VERSION Here Download fast! from Siemens WebPage in "Demosoftware" if we have this demo, we may simulate and create a lot of control projects really perfect to practice

STEP 2: Analyzing Analog Inputs

First watch the differences between Analog Input Types

The Analog Inputs are the Signals between Sensors o Instruments and Control Devices and afther these signals are Scaled by Software we transform this 4-20mA current in a Real Measure getting around 100% of real value, We can scale all important measure types as Temperature (also RTD), Humidity, Pressure, Flow, Toxic Gases and More, all these measures are Analog Signals
Hay 4 tipos importantes:

4-20mA: The most used signal in Sensors/Transmitters because we have less error, and more advantages (we'll see), this is a Current Signal (mA) very Low, the Sensor has the configuration of scale the 4-20mA in a parameter defined by Manufacturer; By example a Pressure range 0-300PSI (defined), 4mA = 0 ; 300 = 20mA

0-20mA: Signal Current (mA) the differences is that the value of sensor 0 means "0mA", nowadays it signals is used but less than 4-20mA (more advantages), Still you can find Sensors with Output 0-20mA

0-10V: The Signal measured in Volts also is very used in Analog Signals (but is most used in Analog Outputs), this have the advantage that is very easy to measure, By example, if Sensor is in half of his range, The Signal in Voltaje is 5V and with a instruments is easy to check

RTD: This is the most exactly and robust way to measure Temperature because the Analog Inputs used are RTD Thermocouple or PT100, that in all PLCs are the best Way to Measure Temperature because It Supports high Temperatures (°C), Also the way of Scale is Easier than a Analog Input in 4-20mA our 0-10V, some Softwares have the options to Read directly RTD, PLC Logo! of course has it, in this chapter dont' see RTD Inputs

In All Softwares The Graphic of Analog Signals and PLC Software Scale use same way, but numbers of Software are differentes, PLC Logo! uses 0-1000; the graphic is designed by a Linear Function

Signal 4-20mA take advantages because:
- It's better for a longer distances
- Considering 4mA as "0" value we can detect faster if any wire is off
- Better Reception to Electronic Noise (always caution)
- Most modern Sensors/Transmitters uses 4-20mA

STEP 4: Wiring and Analyse Details

When we gonna measure Analog Inputs we must to know the Process

In this example we gonna measure Humidity (%), and will activate a Contactor, it means if the value of humidity is higher of a value ON "X" activate the Output and if the value is Lower OFF "X" the Output will be Deactivated

For this Example we choose a Humidity Transmitter Output 4-20mA

Ahora comenzamos a tener nuestra información para una Medición existosa:

Measured Parameter: HUMIDITY
Unit of Measurement: % (Percentage)
Measurement Range: 0 - 100 %
Current Output: 4-20mA
N° Wires: 2-wire, 1 Power and 1 Signal to (+) AI Module
Power Supply: 12-40VDC, in this case with wire (+) from Switching Power Supply 24VDC
Important Consider: Always is important be clear in the enviroment the Sensor/Transmitter Works, always consider to install Sensor avoiding Dust, High Temperatures, Etc, Sometimes Sensores are very Sensitive and it may affect his Signal, of course you want all working nice!

Next is be so clear with the Control Wire Between PLC (AI Modules) and Humidity Transmitter, remember will work with Current 4-20mA

Remember Sensors/Transmitters may be 2, 3 or 4 wires so take care at the moment of choose the Sensor, ALWAYS you must to know the Technical Details, but the concept is the same, if we are Ready with our wiring, So let's Start Programming in Logo! Soft Comfort

Watch the Example Connecting Sensors/Transmitters 2-3-4 Wires in a PLC S7-1200 Siemens

STEP 5: Programming AI in PLC

We are ready with Hardware let's Program in Software

Access to Logo Soft Comfort and start to create the program with follow blocks:

Add block and before to Configure let's Know what means each one:

AI1 This is the Real Analog Input, it means this Input comes directly from the Sensor! of course if the Sensor is connecting in AI1

SF001 This is Analog Amplifier used to Scale the Input 4-20mA VS 0-1000 Software Value

SF001 (Analog Contact) The Value Scaled between 4-20mA y 0-1000; with this value we can begin to scale other values, including our Humidity Sensor, find this Instruction in "Constants" -> "Analog Contact"

SF002 Use this Analog Amplifier to Scale Software Value 0-1000 VS the Value we want to measure, this value is 0-100% wrote in User Manual, here Scale SF001 Value in a new Value called SF002

SF003: This is just an optional block to show how is the "Scaled" between 0-1000 and 4-20mA, we use value similar 40-200 because we can't scale little values, here we scale SF001 in a new Value SF003, when sensor is 0 it shows 40, and when is 100 it shows 200, 50% is 120, So? not bad option to understand

SF004: Analog Threshold Trigger is a Trigger Block, First we Scale SF001 (0-1000) to our Sensor Value same that SF002 (0-100), then configure ON and OFF for prepare when it works, finally you create a "Digital Contact SF004"

SF004 (Digital Contact/Make Contact): This is a Make Open Contact that When SF004 is ON will activate and if is OFF it's not actived

Q1: Normal Output, when is activated SF004 the Output will energize, in this moment we must to know all about these concepts

To Learn Better we recommend to visit Programming First Time a PLC Logo! CLICK before understand better Analog Inputs

Start to Scale and Configure our Analog Inputs, let's configure the Value 4-20mA in Software Value 0-1000:

SF001 will be the direct connection from "AI1", here configure 4-20mA to 0-1000
The Analog Contact SF001 is like a "Output" from the Scaled Value SF001, now the block SF001 has a start value "0" and top value "1000"

Now is the moment to Configure the Software Value 0-1000 in the "Real Value 0-100" and too configure our comparator block 40-200 (similar to 4-20mA)

SF002 is the scaled of 0-1000 in the measurement range of the Instrument, in this case measure Humidity between "0-100% (Measurement Range Specifications), So simple we scale 0-1000 in 0-100

SF002 is scaled in 0-1000 to 0-100 and select "No Sensor", because the Value comes from 0-1000 and SF001 is already scaled from 4-20mA

SF003 in this case is used only to show how works Linear Functions in Analog Signals comparing 40-200 simulating the value 4-20 (mA)

Analog Contact SF001 must to connect in SF002 y SF003 both will scale in a final value

We are almost ready to learn how Activate a Output and how it works

Select Item Threshold Tigger in Instructions -> Analogs -> Analog Thershold Trigger

We must to consider an Analog Contact SF001 to our Block SF004, this is because SF004 too scale values and we scale directly 0-100 value in SF004 (same value than SF002)

Why we scale 2 sames values for SF002 and SF004 (0-100)? both blocks can scale Analog Inputs, but the Blocks are differents, SF002 (Analog Amplifier) don´t have the option to activate or not, but it value is an New Analog Value and can use it in a Analog Contact called SF002, The SF004 (Trigger) is a configurable block that can activate or desactivate (0-1) with a value easy to configure (ON - OFF)

If we are ready and think we have all configurated, Let's Start

SIMULATING ANALOG INPUT SIGNALS

OFF => 0% => 4mA

Simulating 4 differentes values from 0-1000/0-100%, turn on Q1 when % is higher 50

VIDEO ANALOG INPUT SIGNALS

IMPORTANT NOTE
This is just a simple example of how we "Scale Analog Signals" and how it controls Outputs signals to activate, we use SF004 to trigger by ON-OFF but is VERY IMPORTANT mention that in a PLC programming we must to create a better programmation getting a lot of details for a right opepration and less errors, we'll watch more examples, Now is the moment to understand 100% what we did with Sensor in the PLC and Software

STEP 6: Uploading to LOGO!

After every programmation and new knowledge go to Start!

After our program is uploaded to our Logo! (if you have problems goes to) How Connect via ethernet to PLC Logo!, you do click in RUN and READY! The program of Counters has been uploades and is running in PLC Logo! Siemens

QUESTIONS AND ANSWERS

AQUI EL LISTADO DE TUS RESPUESTAS:

Where Can Download Logo Soft Comfort! The Software of PLC Logo? and Buy Original CD?
For the Version DEMO go to Siemens Webpage here or you try in the above external links of Step 2 Here; It Costs around 70 USD (without upgrades) and you can get it in a external company Buy in Automation24 this software may be installed in many computers

What are the most used Analog Inputs in Automation Processes?
Most found are 4-20mA ; 0-10V ; 0-20mA ; RTD (Temperature by Thermocouple), to see all details go to STEP 2 HERE

Why Signal 4-20mA is the most used in Analog Inputs (AI)?
You can find some advantages GO STEP 2 but always is important mention:
- Better for a long distances
- Most tolerant to Electronic Noise (avoiding high values)
- The Current 4mA is point "0", it means always in the measure must be powered, if we don't have Voltage so we have a Wire Break, Never the wire must to be "0 Volts"
- The most choosed signal for a most technology Sensors (really it has advantages)

How can I Start a Project with Analog Inputs?
Sometimes the first time you can find a bit difficult because you are working now with "Softwares and Hardwares", but if you finally understand, Analysis is easier for next projects, always consider next points:
1. Parameter to Measure (Temperature, Pressure, Humidity, etc)
2. Enviroment where the Sensor will be Installed
3. Device and his Signals (4-20mA, 0-10V, etc)
4. PLC (CPU) and Analog Modules
5. Scale the right Measurement range, be attent with Technical Details
6. Measurement Ranges and really how it will affected in the System
7. Right Wiring in Electrical, PLC and Sensors

To Understand fast, what are the steps to understand how Scale 4-20mA in a Real Value?
Vamos a enfocarnos como programamos una AI en PLC Logo!:
1. First we must to have all connected and powered, PLC Logo! + Analog Modules (24VDC) + Transmitter 24VDC (2-3-4 hilos)
2. Then go to Logo Soft Comfort and prepare LADDER Enviroment
3. Select an Analog Contact in "Constants" and the value of the AI in Hardware, in this case AI1 (this port change in place where is connected the Sensor, if it is connected in Port2, the Analog Contact will be AI2)
4. Remember this AI1 is connected with the Current in the Analog Inputs, and the ways how connect 4-20mA and 0-10V are not the same
5. Then Select and "Analog Amplifier" and here we do the First Scaled, in the block we select 4-20mA (AI1 to SF001) and the Range must to be 0 and 1000, this block is called "SF001", it means "SF001" now is scaled from 4-20mA to 0-1000 new value scaled in Software
6. With SF001 already scaled now choose other "Analog Amplifier" and Scale 0-1000 from SF001 in other block and add the "Sensor Measurement Range" now this is a new block with a new value, may be called SF002
7. In this moment SF002 is already scaled (0-1000 to 0-100), an scaled value in a Amplifier don´t is used to activate, is just for Monitoring or scalable for other instructions
8. The moment to activate Outputs ON - OFF is arrived, Select a block "Analog Threshold trigger", and then add a Analogic Contact SF001 connected to New Block Threshold Trigger (already scaled in 0-1000) and use this block for scale in 0-100 and (very important) configure in the options "ON" or "OFF" when the Output will activate
9. Finally Create a Digital Output and called the name of our Threshold Trigger Block (SF00x) When the Block works by the configuration ON - OFF that we have designed the Output is activated
10. More details go to STEP 5 HERE

How I am sure my Connection in Sensor/Transmitter is really well connected?
First consider the power Supply of the PLC (CPU), then the Analog Module 2AI and Sensor/Transmitter are almost always in 24VDC; if you connect right you don't have problem in "burn" any device, then consider the Configuration, Analog Inputs can works independently, so when you connect all your system you can Review and Make Tests of your measurement, if you don't connect any Ouput "Q", AI don't activate anything, nice for practice

I Have a PLC Logo! 24V 24RCE and my Analog Inputs Module AM2 don't work?
It may happens is not strange, because PLCs Logo! powered 24V have incorporated 2 or 4 Analog Inputs (in 0-10V) but it must to be configurated, to see configuration go to Logo Soft Comfort! -> File -> Properties -> I/O Settings -> "Enable 0 AIs" ; it means no one AI in CPU is configurated, so the first "AI1" will be on Analog Module

Why Can't Connect with my PLC Logo?
The Communication with PLC Logo! is by ETHERNET (TCP/IP); you should change your Sub-network number in your computer, remember Logo! comes with 192.168.1.x or 192.168.0.x must to try with both options

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Programming Analog Inputs 4-20mA PLC Logo!

The Analog Inputs are values of parameters mainly Electrical Signals that work with the PLC and are Outputs from Sensors (Transmitters) by Current (0-20mA/4-20mA) or by Volts (0-10V), this value is Scaled in PLC Software and then we have a Real Value very similar to Sensor Value