Contents
What is an analog input module?
The Analog Input Module (AIN) is a key subsystem in the PLC. AINs come in many variations to condition real world physical parameters, such as, Temperature, Pressure, Force, or Strain. Typically, these AIN inputs are command signals in both voltage (e.g. ±10V) and current form (e.g. 4-20mA).
Is PLC analog or digital?
Common PLC input/output (I/O) can be analog and/or digital. An analog signal is one whose value continually varies over time. They are best represented as a continuous signal like a sine wave. Each point on the wave has a precisely defined value.
What is the IEC system protection for precision analog inputs?
IEC system protection for precision analog inputs. IEC 61000 is the standard that covers EMC robustness at the system level. The three sections of the standard that deal with high voltage transients are IEC 61000-4-2, IEC 61000-4-4, and IEC 61000-4-5.
How are analog input and output pins protected?
The analog input and output pins of a modern IC are typically protected against high voltage electrostatic discharge (ESD) transients. The human body model (HBM), machine model (MM), and charged device model (CDM) are the device-level standards used to measure a device ’ s ability to withstand ESD events.
How does an input clipping diode protect the input?
Figure 13: Reading high voltage inputs. The input clipping diode to ground is to protect from less than zero volt spikes. The input clipping diode to the positive bus is removed in favor of the zener diode after the current limiting resistor. This provides a known voltage for the input pin and reduces the amount of current shunted to the power bus.
What’s the best protection for a digital input?
For most digital inputs, a good value is between 100 Ω and 10 kΩ. For our system, a value of 1 kΩ is used. Figure 6: Current limit protection for an input. This type of protection works well for short wire connection lengths and enclosed wire runs (little chance of EMI, etc.).