Factory Acceptance Testing Checklist

  • How do you test digital outputs with factory acceptance tests?

In a digital control system, like a programmable logic controller (PLC) or a microcontroller, a digital output is a type of output signal. A digital output signal is a binary signal, which means it can only be “on” or “off.” These transmissions are employed to turn on or off multiple devices. In a digital control system, the control device generates the digital output signal, which is then transferred to the controlled device via a communication interface.

With that being said, a common question we receive here at Keltour is, “how do you factory acceptance tests digital outputs?” Therefore, to ensure you’re able to gain further knowledge about digital outputs, and site acceptance tests, to learn the answer to this question, keep reading about our factory acceptance testing checklist!




What are digital outputs?


As we mentioned earlier, a digital output is a form of output current in a digital control system, like a programmable logic controller (PLC). A digital output signal can only have two positions: “on” or “off.” These signals are applied to turn on and off different devices. The unique aspects of a digital output signal, including operating voltage safety inspection and current capacity, are determined by the application’s needs and the parts utilized.

Digital outputs, in general, offer a high level of precision and accuracy because they’re on/off state and can be precisely regulated and monitored to acceptance criteria, and they are broadly used during commercial and industrial control systems to handle numerous types of testing equipment and entire fat procedure with hazard identification fat checklist.

What is a digital output example?


Now that you have a more comprehensive understanding of what a digital output is, let’s take a closer look at some examples of digital outputs that are used in our everyday life:

  • Lights: Digital outputs can be used to turn lights on and off.
  • Motors: Digital outputs can be used to start and stop motors
  • Valves: Digital outputs can be used to open and close valves, such as in fluid or gas control systems.
  • Alarms and warning signals: Digital outputs can be used to activate alarms and warning signals, such as flashing lights or sirens, to indicate a fault or alarm condition.
  • Heating and cooling systems: Digital outputs can be used to control the operation of heating and cooling systems, such as turning on and off fans, pumps, and valves.
  • Conveyor systems: Digital outputs can be used to control the operation of conveyor systems, such as starting and stopping the conveyors.
  • Digital control signals from PLC (Programmable Logic Controllers): used to control industrial machines and processes.
  • Digital signals from sensors: used to transmit information from sensors, such as temperature or pressure, to control systems.

What is the difference between analog and digital output?


Analog and digital outputs are two kinds of output signals that are used in control systems. The primary distinction between the two is how data is represented and transmitted.

Analog outputs are consistent signals that can reflect any value within a specified range, such as current or voltage. Analog outputs are frequently used to control devices or processes that necessitate a continuous or seamless control signal, such as motor speed or heating element temperature.

In contrast, digital outputs are binary signals that control “on” or “off” requests. Digital outputs are employed to turn on or off devices or processes, including lights, motors, or valves, as we mentioned above. Analog outputs, in general, offer a high degree of precision and resolution because they can embody any value within a specific range. They do, however, necessitate more expensive and complex equipment reliability, such as analog-to-digital adapters and power amplifiers, to be utilized successfully.

On the other hand, digital outputs are simpler and less costly because they only need to transfer a binary signal. However, because they can only represent states, they are less precise and versatile than analogue outputs, and they may not be appropriate for applications that necessitate a seamless control signal.

How does digital input-output work?


A digital input/output (I/O) system controls the flow of digital signals among a number of devices. Input and output devices are linked to a control system, like a programmable logic controller (PLC), microcontroller, or computer, in the digital I/O system. The digital input systems receive binary signals from outside sources and transform them into signals that the control system can handle.

The control system sends signals to the digital output devices, which convert them into binary signals that can be used to control external devices or processes. A digital output device, for example, may receive a signal from the control system implying to either turn on or off a light or whether to start or stop a motor.

The control system is in charge of digital processing inputs, making choices based on the data, and transmitting instructions to digital outputs. To carry out this function, the control system employs a program or algorithm which can be written in a range of programming languages.

How do you tell if a signal is analog or digital?


Analog and digital signals can be distinguished by observing their behaviour and properties. The primary distinction between analogue and digital signals is that analogue signals can represent any value within a specified range, whereas digital signals can only depict specific, predefined values.

You can observe a signal’s behaviour and properties on factory acceptance test checklist, such as its waveform and the range of values it can represent, to determine whether it is analogue or digital. Furthermore, test equipment such as an oscilloscope or logic analyzer can be used to measure the properties of a signal and determine whether it is analogue or digital more accurately.

How do you test digital inputs at PLC?


Furthermore, to test digital inputs at PLC to applicable standards, you will need to do the following factory acceptance testing checklist:

  1. Connect the input device to the PLC: This may involve physically connecting the input device to the PLC using cables or connecting wirelessly if the device supports it.
  2. Configure the input in the PLC software: This involves specifying the input channel or address, and input types, such as a switch and setting any necessary parameters, such as debouncing or filtering.
  3. Monitor the input status in the software: This can be done through a dedicated input monitoring screen or by viewing the input status in the program or ladder logic view.
  4. Apply the input signal: This involves physically triggering the input device, such as by closing a switch or applying a voltage.
  5. Observe the change in the input status: The input status should change in the PLC software to reflect the signal being received.
  6. Repeat for all inputs to be tested: Repeat the process for each individual input to be tested.

During this process, it is essential to keep a record of the test results for future reference, in case of any issues like incomplete materials data sheets or for maintenance personnel purposes. This can be done through software reports, spreadsheets, or reference documents.