We turn our attention to something every universal I/O module must handle: Voltage Input Measurement. At first glance, reading a voltage sounds trivial. But in real-world industrial systems, it rarely is. I Voltage Input Measurement requires consideration of numerous and diverse factors, including signal input ranges, type of input signal, measurement accuracy, and robustness. The AD74416H simplifies design by integrating advanced features to streamline the implementation of reliable and precise voltage measurements. In earlier blogs in this series, we explored how software configurable I/O (SWIO) simplifies industrial designs, from adaptive power switching for thermal management to flexible voltage and current outputs.
Voltage Input - Simple Industrial Solution
Voltage inputs are generally considered less robust and more susceptible to noise and interference when compared to current loop signaling. In industrial environments, where long cable runs, electromagnetic interference (EMI), and grounding differences are common, this perception often leads designers to favor 4–20 mA current loops. However, voltage inputs remain highly relevant and widely used, especially in applications involving short cable distances, cost-sensitive designs, or direct interfacing with sensors and legacy systems.
Despite these challenges, voltage input solutions can be implemented effectively when the right level of integration and configurability is available. This is where the AD74416H simplifies the design process. Rather than relying on a collection of external components, precision resistors, protection networks, filtering stages, and ADC front ends integrate key building blocks required for robust voltage acquisition.
Voltage Input Demonstration on the EV-AD74416H-ARDZ
To demonstrate the Voltage Input capability on the physical hardware, use the EV-AD74416H-ARDZ board setup and ACE. In a single-ended voltage configuration, the input voltage signal is directly connected to I/OP_x and I/ON_x terminals. Potentiometer RT can be used to easily adjust the input voltage. Connect the potentiometer's midpoint to the onboard voltage AVDD_LO (~ 13V) to allow easy adjustment of the input voltage.
Figure 1: EV-AD74416H-ARDZ Voltage Input channel connection
Once the physical connection to the channel is complete, configure Voltage Input (VIN) using the dropdown menu. Set ADC to convert the input voltage by configuring CONV_SEQ to CONTINUOUS and enabling the corresponding channel conversion by ticking CONV_x_EN., Click the apply button, then load the setting to the device. The figure below shows an example of channel A configuration; the calculated input voltage can then be read next to the enabled channel configuration.
Figure 2: AD74416H ACE plugin, Voltage Input Configuration
In practical applications, the source of the voltage input signal would typically be a sensor, that uses voltage as the primary analog variable to indicate the measured physical quantity, such as pressure, temperature, or position.
Typically, the sensor's input voltage signal ranges from 0 V to 10 V, a standard widely adopted in industrial applications. Sensors and transmitters often use this range to represent a physical quantity in a linear manner. For instance, 0 V corresponds to the minimum value and 10 V to the maximum full-scale reading. In practice, however, signals may occasionally exceed this nominal range due to sensor tolerance, fault conditions, or transient events.
Such overrange conditions must be properly handled by the input circuitry to avoid measurement errors or potential damage. A robust voltage input design needs to detect and safely process overrange signals while maintaining accurate measurement within the valid operating range.
AD74416H integrates the ADC_ERR status flag, which indicates that the input voltage is outside the configured range (CONV_RANGE). Adjust the input voltage source beyond the configured input voltage range and observe that the ALERTS tab will indicate ADC_ERR.
Robust Voltage Input Diagnostics with Integrated Burnout Currents
In addition to handling nominal input ranges, robust voltage input designs must also address fault conditions such as disconnected sensors. In voltage-driven systems, an open circuit can go unnoticed because a floating input may appear as a valid measurement (for example, near 0 V). To address this, the AD74416H integrates burnout current sources in voltage input mode.
These very small currents introduce a controlled bias on the input pins, ensuring that an open-circuit condition forces the measurement toward a defined limit, making fault detection reliable and deterministic. When the sensor is connected, the induced error is negligible due to the low current magnitude, but when the input is open, the resulting shift in measured voltage clearly indicates a fault.
AD74416H allows the user to configure the Burnout Current of both polarities (SINK_CURR or SRC_CURR) with a range from 100nA to 10μA (BRN_VIOU_CURR). Current sources for burnout can be enabled in the ACE plugin under the I_BURNOUT_CONFIG configuration. The figure below highlights the burnout's current operation.
Figure 3: Voltage Input Configuration, Burnout Currents
From Challenge to Confidence in Voltage Input Design
Voltage input may seem straightforward, but achieving robust, industrial-grade performance requires careful attention to accuracy, protection, and diagnostics. The AD74416H simplifies this challenge by integrating key features, from flexible configuration to fault detection, into a single device.
By leveraging the built chip capabilities mentioned, designers can confidently implement reliable voltage measurement solutions while reducing complexity, cost, and development time, ultimately increasing the intelligence and resilience of modern industrial I/O systems.
Read all the blogs in the Configurability IQ series.