PLC Analog Inputs and Signals

==========================

✅ Check out the full blog post over at

==========================

In this video, we are going to be talking about analog inputs to the PLC.

What do we mean by analog input? Analog values are continuous values, such as temperatures and pressures.

While we tend to think of them in digital terms, at some point we have to convert them from the continuous world into our digital world, and this is where analog inputs come in.

Voltage signals in the range of plus or minus 20 volts or so and current signals in milliamps are commonly used as both analog inputs to PLCs.

Every PLC manufacturer has I/O modules to deal with these kinds of signals, along with other, more specialized modules.

==========================

Missed our most recent videos? Watch them here:

=============================

To stay up to date with our last videos and more lessons, make sure to subscribe to this YouTube channel:

=============================

=============================

=============================

A special thanks to Frederico Duarte Fagundes for translating this video.

#RealPars #PLC #PLCanaloginput

[santopino]

I would add that some of the most important reasons why 4-20mA is used over 1-5V:
1. The voltage reading could be inaccurate due to cable resistance voltage drop.
2. The current read in the transmitter and the PLC are identical, for any value of cable resistance, thus the transmitter can sense if the current is not the correct value it intended to transmit so it can adjust its impedance in line to bring back the current to the correct value.
3. Two wire transmitter connects are possible with current but not with Voltage.
4. Under ange (lower the 4mA), over range (higher than 20mA), and wire break (under 3.2mA) can interpreted by the PLC.
5. Current circuit is a very low impedance (normally less than 750 Ohms) so less sensitive to electrical interference compared to Voltage signals.
6. Current circuits allow an easy connection of an indicator in the current loop as long as the total resistance in the loop does not exceed typically 750 Ohms.

[picable]

Hello Sir..
All your videos are very helpful for us. Kindly make more similar detailed videos on PLC, HMI, SCADA, DCS etc..
Thankfully you all....

[samerbarakat-diab]

wonderful introductions. Watched it over a period of hours to absorb the wealth of information provided. Thank you for making your videos available on YouTube.

[marioorecarrion]

Great information, the way you explain it is clear and direct!!!

[ardentdfender]

Great video. I’m also wondering if you all could do a video on the process of Instrument Loop Checking and proper loop checking from the field device to Terminal Blocks to the PLC Input/Output cards in making sure instruments/devices are properly connected and or scaled.

[eugenepohjola]

Howdy. Nice as usual.
Some discussion about measurement precision might be in order.
Let's take two pressure transmitters from the same manufacturer. One is 0 - 1 bar and the other 0 - 10 bar. Both have a precision of 0, 5 %.
What does this mean ? For the first one ( 0, 5 / 100 ) x 1 bar = 5 millibar. For the latter ( 0, 5 / 100 ) x 10 bar = 50 millibar. The accuracy bandwidth for the first is + - 5 millibar over the whole measuring span and for the latter + - 50 millibar over the whole measuring span.
What is the accuracy bandwidth ? It is the + - standard deviation which, somewhat simplified, means that 2 measurements of 3 are inside the bandwidth.
Alright. Now the plant manager says he wants to reduce the stock of spare parts and orders the 1 bar type to be removed from the stock replenishing program. Just use the 10 bar type and multiply the reading by 10 in the PLC.
What is wrong with this approach ? Let's say we have a reading of 0, 8 bar. With the original transmitter the actual value can be 805 millibar but with the replacement as much as 850 millibar. This much a deviation could ruin a production batch.
Regards.

Great place to start learning and helps to get image how this works. Thanks

[adilsaiyad]

Hello RealPars,
Thank you so much for your quality explanation videos.
I have a request.
Can you make one video series for practical Industrial Project ?
In that series, u will provide the information about how exactly PLC project is approached in actual environment.

[balachandar]

super videos easy to learn devices .kindly detailed videos on plc, dcs, scada ... thank you REAL PARS TEAM

[mrae]

Just came across your channel it’s great
I’m have my new parents watch them because of the lack of understanding PLC’s and I’m retiring soon and they will be handling the maintenance and repairs on specialized equipment we work on

[ethanjohnstone]

Awesome channel !
I Work at a Waste water Treatment Plant in Sydney Australia, which we use all this gear here.

So goods to have such a refresher on how things work!

Have you guys thought about doing more instrumentation videos ?

[josecastellanos]

Awesome video !! I suggest you should post videos about the programation languages of a PLC

[santhoshdsp]

thank u bro i have clearly understood analog with ur video

[pcrb]

Dear Real Pars Team,
I have few doubts,
1) What is meant by "Conditioned Input"?
2) What is the math behind for choosing 500 ohms in the PLC AI Circuit? I mean how we derived the load resistance as 500 ohms kindly explain it in detail with calculations?
Thanks in advance
Best Regards,
PC Raju.

[mounesh]

Thank you for your job..
I request you to add some videos on analog input to PLC and how to program it.. please..

It's been very helpful from your videos..
I hope u will do the need

[mohibullahkhan]

I consider myself lucky that i found your channel.

[theodoreroberts]

Information needed. How many analog outputs (maximum) can a PLC, or other additional elements control? Using as an electrical switcher.

[kathi]

Hi RealPar, I have a request, can you please elaborate more about different types of signals used in instrumentations.. Thanks in advance

[elcinaliyev]

Thanks a lot for these wonderful videos

[Vai_kun_chee]

Please let me know how to measure the AI and AO signal on the IO modules with multimeter