DA-Converter

Digital-to-Analog-Converter

Digital-to-Analog-Converters are a common electric component. Digital-to-Analog-Converters are used in different branches of electric technology. Within the industrial sector they’re used to transfer IO-Link^(R) or other signals. Other areas of application include consumer electrics as well as messaging technology.

What is a D/A-Converter?

D/A-Converter is short for Digital-to-Analog-converter. The basic functionality of D/A-converters is  the translation of digital signals into analog signals. IO-Link requires Digital-to-Analog-Converters to translate digital signals of the control unit (SPS) into analog signals that are being used by an analog field device such as an actuator. Analog signal transmission presents a much higher risk of interference than digital signal transmission. In general it is recommended to put Digital-to-Analog-Converters as close to an IO-Link field device as possible  to keep the length of the analog cable as short as possible. They should be prepared for dangers such as dirt, dust, humidity and vibration. By complying to the standards IP65 and IP67 these IO-Link components are prepared for industrial use.

Functionality of a D/A-Converter

A digital signal has defined values at a defined point of time. This signal is discrete. Defined pairs of value and time exist. At times in between these defined pairs there is no value being displayed by the signal. Translation into a continuous signal is impossible. To translate into a continuous signal a fitting method has to be chosen. Accuracy and speed of the translation are determining factors for a continuous output signal.

Multiple steps are required to translate a digital signal into an analog signal. At first discrete digital values are translated into a time continuous signal. The voltage equivalent to the digital value is maintained until the next digital signal is available. The time period in between two digital signals depends on the rate. This results in a step-like graph. During the next step, filters are used to get rid of deflective signal characteristics. In the last step linear distortions are removed with additional filters. Quantization errors of a previously used analog-to-digital-conversion may distort the signal when translated back to an analog signal.

D/A-Converters - Application

Translating IO-Link signals in analog signals is an interesting application of digital-to-analog-converters. It allows the use of analog devices such as sensors and actuators. Translation of IO-Link to analog enables connection of a divers variety of field devices to machines or plants. Such devices transmit analog values such as temperature, pressure or distances to these machines or plants. IO-Link compatible D/A-converters have to be used since not all sensors include the required electric set-up to translate analog values into digital values required within IO-Link. Actuators that require an analog input signal are dependent on a translation of digital values into analog values as well. These devices are available for IO-Link too.