Podcast
Questions and Answers
What is the primary reason for using a 4 to 20 milliamp current range for analog input instead of 0 to 20 milliamp?
What is the primary reason for using a 4 to 20 milliamp current range for analog input instead of 0 to 20 milliamp?
Which of these is NOT a component involved in the analog input process?
Which of these is NOT a component involved in the analog input process?
What is the primary function of the transmitter in an analog input system?
What is the primary function of the transmitter in an analog input system?
What is the purpose of the analog to digital converter (ADC) in the analog input process?
What is the purpose of the analog to digital converter (ADC) in the analog input process?
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Why is it important to have an offset in the analog input range, such as starting at 4 milliamps instead of 0 milliamps?
Why is it important to have an offset in the analog input range, such as starting at 4 milliamps instead of 0 milliamps?
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Which of the following is NOT a typical example of a sensor used in an analog input system?
Which of the following is NOT a typical example of a sensor used in an analog input system?
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Study Notes
Analog Inputs
- Analog inputs are more complex than digital inputs because they involve sampling a signal that changes over time, such as temperature or tank level.
- These signals are not simply 1 or 0, but rather a continuous range of values.
Measuring Real-World Phenomena
- Analog input devices convert physical world signals into a digital representation.
- Example: a level meter measures the height of a tank and transmits a value between 4 and 20 milliamp current.
Avoiding Errors with Offset
- When setting the measuring range, it's good practice to avoid starting from 0 milliamps to detect faults such as power outages or corrosion.
- This is because a faulty connection (e.g., a cut wire) would result in a 0 milliamp reading, but the tank level would not be at 0 feet.
- Instead, the "empty tank" measurement should be represented by a non-zero value, such as 4 milliamps.
Analog Input Components
- The sensor itself (e.g., flow sensor, level sensor, temperature sensor) contains a transmitter that sends a signal.
- The signal is transmitted as 4 to 20 milliamps.
- The analog input controller card samples the current and converts it to a digital value through an A-to-D (analog-to-digital) process.
Analog Inputs
- Analog inputs are more complex than digital inputs because they involve sampling a signal that changes over time, such as temperature or tank level.
- These signals are not simply 1 or 0, but rather a continuous range of values.
Measuring Real-World Phenomena
- Analog input devices convert physical world signals into a digital representation.
- Example: a level meter measures the height of a tank and transmits a value between 4 and 20 milliamp current.
Avoiding Errors with Offset
- When setting the measuring range, it's good practice to avoid starting from 0 milliamps to detect faults such as power outages or corrosion.
- This is because a faulty connection (e.g., a cut wire) would result in a 0 milliamp reading, but the tank level would not be at 0 feet.
- Instead, the "empty tank" measurement should be represented by a non-zero value, such as 4 milliamps.
Analog Input Components
- The sensor itself (e.g., flow sensor, level sensor, temperature sensor) contains a transmitter that sends a signal.
- The signal is transmitted as 4 to 20 milliamps.
- The analog input controller card samples the current and converts it to a digital value through an A-to-D (analog-to-digital) process.
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Description
Learn how to sample and represent physical world inputs like temperature and tank levels using analog input devices and convert them into digital values.
