Factory Acceptance Test Explained - Part 2 | PLC Digital I/O Test

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⌚Timestamps:
00:00 - Intro
01:29 - Simulated signals
01:59 - Step 3) Test the PLC digital inputs
03:31 - Passive and active devices
04:25 - Step 4) Test the PLC digital outputs
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When performing a FAT for a control cabinet that includes a PLC, one of the most important things to test is the PLC inputs and outputs.
Depending on your application, you may have different input and output cards for your PLC.
To do a FAT you need to test each of the PLC inputs and outputs one by one and make sure everything works properly based on the PLC logic.
But you may ask “how can I do this while the control cabinet is still not installed on the site and there are no actual sensors or actuators connected to it?”
The answer to this question is simulated signals. You need to use simulated signals to perform your Factory Acceptance Test.
Step 3) Let’s start with the digital inputs first. The PLC digital inputs are connected to the upside of DI terminals. The other side of the terminals will be connected to the switches and sensors once we take the cabinet to the site.
But since we have some switches on the control cabinet door such as a mute buzzer, ESD Reset, and Emergency Stop, we have already wired these input devices to the other side of the terminals and we already have them connected to the relevant PLC digital inputs. Let’s start our test with these switches first.
We’ll start with the mute buzzer input. Let’s say that this push button is connected to the first digital input of the PLC. To test this input, all you need to do is to press the push button and see if the LED light for the first digital input on the card turns on.
If the LED does not turn on when you press the push button, it means that there is something wrong with the wiring.
In this case, you need to take the panel wiring diagram and follow the wiring on the panel and fix the issue.
Moving on to test the rest of the PLC digital inputs, if the device that will be connected to the digital input is passive, like a simple switch, you can simulate the signal by connecting a piece of wire to the terminal blocks.
However, if the device is active, you need to look at the wiring diagram and find the best way to simulate the signal coming from that active device.
In most cases, you can make use of a simulator. A simulator is a device that can accurately reproduce a sensor output.
Step 4) After you’re done with testing the digital inputs, you can move on to testing the digital outputs. The digital output card that we have sends a 24-volt signal to various devices connected to individual output terminals.
A digital output could be connected directly to an output device like a buzzer or a relay that could operate an actuator like a motor.
To test each output we just need to give the PLC an input signal and see if the digital outputs change as expected based on the PLC program.
The first digital output that we have here is connected to a motor via a contactor. The PLC program logic, says when the level switch 1 and level switch 2 are both active, we need to have the motor connected to this output turned on.
To test the output, all you need to do is to activate the inputs using simulated signals and see if the contactor on the output will be energized.
If the contactor is energized, it means all the wiring and the PLC logic works perfectly fine for this output. If not, you need to review your wiring using the wiring diagram.
You can do the same to test the rest of the PLC digital outputs.
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To learn more, you might want to review our other articles:
What is an Instrument Calibrator? realpars.com/instrument-calib...
How to Follow an Electrical Panel Wiring Diagram realpars.com/panel-wiring-dia...
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Пікірлер: 46

  • @JKTCGMV13
    @JKTCGMV133 жыл бұрын

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    @realpars

    3 жыл бұрын

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    3 жыл бұрын

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    @JKTCGMV13

    3 жыл бұрын

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    @UsherWolheim3 жыл бұрын

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    @realpars

    3 жыл бұрын

    That means a lot, Usher! Thanks for sharing that with us. If you have any questions while watching our video courses, please feel free to contact us at any time! Thanks again and happy learning!

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    @frednewcal93883 жыл бұрын

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  • @realpars

    @realpars

    3 жыл бұрын

    Thanks a lot! Great to hear that, Fred

  • @bushramusa8729
    @bushramusa87292 жыл бұрын

    This channel is tailored for me and my career needs. If you can make videos for failures inspection and maintenance plans. It will be awesome

  • @realpars

    @realpars

    2 жыл бұрын

    Hi Bushra, Thanks for the topic suggestion, I will definitely go ahead and forward this to our creator team. Happy learning!

  • @khalidahmad9563
    @khalidahmad9563 Жыл бұрын

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  • @realpars

    @realpars

    Жыл бұрын

    That's great, Khalid! Thanks for your support.

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    @prasannahukkire34093 жыл бұрын

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  • @benjieramos4887
    @benjieramos48873 жыл бұрын

    More for how to use the simulator..thank you from phil.

  • @AbdullahAhmed-vj2vi
    @AbdullahAhmed-vj2vi3 жыл бұрын

    I like your videos. We need more . Also we need video that explains wiring digital input and output step by step

  • @realpars

    @realpars

    3 жыл бұрын

    Hi Abdullah, Thanks for your comment and topic suggestion! I will happily go ahead and pass this on to our course developers. In the meantime, the following video course might be helpful as well kzread.info/dash/bejne/oI1krsOFqNjZmNI.html

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    @SEALTRONICS Жыл бұрын

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    @realpars

    Жыл бұрын

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  • @Halesh1305
    @Halesh13053 жыл бұрын

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  • @realpars

    @realpars

    3 жыл бұрын

    Glad to hear that, Halesh!

  • @darshanacollection6646
    @darshanacollection66463 жыл бұрын

    Good job sir.👍👍

  • @realpars

    @realpars

    3 жыл бұрын

    Thank you!

  • @anoopgeorge9483
    @anoopgeorge94833 жыл бұрын

    Very useful video 👌

  • @Halesh1305

    @Halesh1305

    3 жыл бұрын

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  • @realpars

    @realpars

    3 жыл бұрын

    Thank you!

  • @ahmad.a.alhussain
    @ahmad.a.alhussain2 жыл бұрын

    Great channel. I've followed you on LinkedIn immediately. but about the test, I have faced another issue the names in the circuit diagram (the names of components in the factory) were different from the site and that made a problem by wasting the time to understand the right wiring type.

  • @realpars

    @realpars

    2 жыл бұрын

    Part of commissioning is to match the actual device in the field with what is shown on the wiring diagram. If I have a digital input or digital output card, most devices with one of two types (contact closure or 3-wire solid-state). I have had the same thing happen over the years, but with a little practice, you will be able to quickly match the field instrument to how it should be wired to the PLC. As a side note, I would also ask the engineering company who designed the system to explain the discrepancy between the field device and what is on the wiring diagram. There may be bigger issues (working off of old drawing revisions, missed updates, mislabeled devices, etc.).

  • @ricardogarcia3900
    @ricardogarcia39003 жыл бұрын

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  • @Ravinder764
    @Ravinder7643 жыл бұрын

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  • @clems6989
    @clems69892 жыл бұрын

    90% of problems during initial testing are wiring issues. The other 90% is component configuration...

  • @Amalokch
    @Amalokch3 жыл бұрын

    04:50, what if the PLC logic is too complex to simulate? Isn’t much better for I/O testing force the output signal and see if the relay or contact activates?

  • @realpars

    @realpars

    3 жыл бұрын

    It is always better to engage the actual hardware components in any simulation or system logic checks. Most often, this is not possible since the hardware and I/O may be in the process of being installed in the field at the time testing is required. A good simulation, regardless of the complexity of the software and logic, should be designed to tie "outputs back to inputs" and allow for direct input of analog values. Full dynamic simulations are usually possible as well but take longer to plan and set up. You need to decide what level of simulation/program checkout is appropriate for your needs. Typically, it will take 5%-10% of the time taken to create your program logic to create a "tie-back" simulation; 10% - 20% for a full dynamic simulation. Your simulation and testing strategy should be part of your Functional Specification document and needs to be planned for up front. When I program PLCs, my control module logic (device control logic) and equipment module logic (equipment functional logic) have simulation code built right into the logic. When I need to simulate the system at the "tie-back" level, I simply need to set the simulation bit. If I need to do a full dynamic simulation, I add a program block or file to do all of the necessary calculations and setting of analog values. Don't forget the power of your HMI interface in setting conditions and monitoring the logic!

  • @Amalokch

    @Amalokch

    3 жыл бұрын

    @@realpars Many thanks for the feedback, as you explain seems to be having a simulation program block might help in the long run. I will try it next time. cheers!

  • @davorbozic8430
    @davorbozic84308 ай бұрын

    I would only add the information that it is easier to just force the digital outputs in your PLC one by one. Its straightforward and easy process, and you don't have to go inside the program logic and check the trigger conditions.

  • @realpars

    @realpars

    8 ай бұрын

    Thank you for adding that! We very much appreciate that.

  • @ardentdfender4116
    @ardentdfender41163 жыл бұрын

    This is what you call “Loop Checking”.

  • @cck1496
    @cck14963 жыл бұрын

    Excellent video. Can anyone tell please how to simulate the signal? Do you mean to jumper it? I am trainee. Thanks.

  • @realpars

    @realpars

    3 жыл бұрын

    Yes, digital inputs can be simulated by jumpering the appropriate voltage from a power supply to the input terminal of the PLC. This is electrically what would exist if the input device were energized. This can be dangerous if you are not experienced in doing this. 24VDC circuits from different power supplies should not be mixed. Always use power from the same power supply circuit as would normally be used by the device. Analog inputs can be simulated with a Fluke process meter or other devices that can generate 4-20 ma for loop-powered devices. For Profibus PA sensors, there is a simulation mode that allows testing of the analog signal to the PLC. Digital outputs and analog outputs should be forced from the PLC to simulate.

  • @cck1496

    @cck1496

    3 жыл бұрын

    @@realpars Thanks for your prompt and such detailed explanation. Thanks for sparing your valuable time. Really appreciate your excellent work. Keep it up...

  • @alex_nevskiy_888
    @alex_nevskiy_8882 жыл бұрын

    For DO why not just use Watch Table Force Mode for it? The DOs inclusion conditions in program may be anaccessble at all, for example they can include time delays, some inner flags or variables.

  • @realpars

    @realpars

    2 жыл бұрын

    Yes, you could certainly use this method for testing DO points. Many times, if the logic is simple or repetitive, such as with valves, it may be better to test the logic as well as the outputs at the same time. The method of testing is up to the engineer performing the test.

  • @alex_nevskiy_888

    @alex_nevskiy_888

    2 жыл бұрын

    @@realpars Ah, got it.

  • @mehulpatel9579
    @mehulpatel95792 жыл бұрын

    👍🏻🇮🇳

  • @vickywagh6860
    @vickywagh68603 жыл бұрын

    How can we test outputs if program not downloaded to PLC

  • @realpars

    @realpars

    3 жыл бұрын

    Technically, you can't. Triggering an output on a PLC output card has to be done via logic or via a "force", both of which require a connection to the PLC. You can load a "bare-bones" hardware configuration with no program elements and force the outputs.