Integrated Closed Loop Control: Embedded Intelligence for Real-Time Pressure Regulation

Advanced Pressure Sensor Implementations Demand Sub-Millisecond Feedback Architectures

Modern closed-loop control systems use real-time feedback to autonomously regulate processes to specified setpoints with minimal latency and maximum precision. These systems integrate sensing, computation, and actuation elements that continuously measure system variables, compute error signals, and generate corrective actions to minimize deviation from target operating conditions. In modern systems, edge computing architectures enable control loops to operate at kilohertz frequencies without microcontroller intervention.

Figure 1:  Standard Control Loop System

Differential pressure sensors are critical for flow, level, and density measurements across biomedical devices, industrial automation, aerospace systems, automotive powertrain management, renewable energy systems, and smart building HVAC networks. These sensors typically provide analog or digital outputs that feed into control algorithms.

Legacy Control Loops: Bottlenecks and Limitations

Conventional implementations rely on external microcontrollers or DSPs to execute control algorithms, introducing several systemic inefficiencies:

1. Latency Accumulation: Multi-stage signal chains (sensor → ADC → MCU → processing → DAC → actuator) accumulate delays of 5-50ms, creating phase lag that destabilizes fast dynamic systems and limits control bandwidth to <100Hz.

2. Computational Overhead: Real-time control requires high-performance ARM Cortex-M7-class processors (≥400 MHz) with floating-point units, consuming 50-200 mW and requiring thermal management in compact enclosures.

3. System Complexity: Discrete-component architectures require careful PCB layout for signal integrity, analog front-end design for ADC interfacing, and sophisticated firmware for control-loop tuning and stability analysis.

4. Quantization and Sampling Artifacts: External ADCs operating at typical 1-10 kHz sampling rates introduce aliasing and quantization noise (typically 12-16 bit resolution) that propagate through the control loop, necessitating oversampling and digital filtering.

5. Determinism Challenges: RTOS-based control implementations face jitter due to interrupt latency, task scheduling, and context switching, compromising the loop timing consistency critical for industrial safety certification (IEC 61508, ISO 13849).

6. EMI Susceptibility: Long analog signal paths between the sensor and controller act as antennas for electromagnetic interference, requiring extensive shielding and filtering that increase cost and footprint.

NimbleSense™ Architecture: Silicon-Integrated Loop Control

Incorporated into all our differential pressure sensors, Superior Sensor Technology’s proprietary NimbleSense architecture combines processing intelligence, signal-path integration, and algorithms to create modular building blocks that are easily selectable to support a wide array of applications. One of the building-block components in NimbleSense is a closed-loop controller, enabling the company to incorporate this function directly into certain sensor products. This optional capability eliminates the need to design and implement a complex control-loop system, resulting in more efficient, more reliable, and less costly products.

Superior Sensor’s CLC adds control capability to set and maintain flow rates by measuring pressure within the sensor. It can directly control motors, valves, and actuators to maintain flow rate targets. The integrated CLC design significantly reduces loop delays in the electronic circuit by up to 100x.   

Noise-Aware Control: Filtering Before It Becomes an Error Signal

In traditional systems, mechanical and electrical noise often enters the loop before control calculations are performed. This noise is then amplified by the control algorithm, creating instability and degraded accuracy.

NimbleSense closed-loop control operates on digitally filtered pressure data, ensuring:

• Mechanical vibration is removed before the control action
• ADC quantization noise does not modulate actuator response
• Flow ripple does not destabilize the loop

This noise-aware architecture allows control loops to operate at higher gains while maintaining stability, thereby directly improving regulation precision

Figure 2:  Closed Loop Control – Air Quality Application Example

Figure 2 shows a block diagram of an implementation of the Superior Sensor CLC for an air quality application. To effectively measure air quality, we must maintain a constant, known airflow through the viewing window. The differential pressure across the venturi directly measures the flow into this viewing window. The system sets a target pressure across the venturi, and the differential pressure sensor automatically increases or decreases the pump drive to maintain the targeted differential pressure, ensuring a constant airflow into the viewing window. This is accomplished with the NimbleSense closed-loop circuit and, when used in combination with the company’s proprietary noise filtering (topic for another blog post), results in greater than a 100x reduction in loop delay.

Target Applications and Use Cases

The NimbleSense closed-loop control capability addresses critical requirements in:

• Respiratory Care: Ventilators, CPAP/BiPAP devices, oxygen concentrators, and anesthesia delivery systems requiring rapid pressure regulation during patient breathing cycles
• Industrial Automation: Pneumatic actuator control, spray coating systems, semiconductor fabrication gas flow management, etc.
• Building Systems: VAV boxes, demand-controlled ventilation, cleanroom pressurization, laboratory fume-hood face-velocity control, etc.
• Automotive: Turbocharger wastegate control, EGR valve positioning, fuel vapor management, battery thermal management
• Renewable Energy: Hydrogen fuel cell reactant flow control, biogas processing, concentrated solar thermal systems
• UAVs: Speed, angle of attack, and altitude verification

Conclusion: Control Is Becoming a Sensor Function

As systems move toward higher integration, lower power budgets, and tighter performance margins, control architectures must evolve. Embedding closed-loop control directly in the pressure sensor fundamentally changes system design:

• Measurement and actuation become tightly coupled
• Latency becomes deterministic and minimal
• System reliability and efficiency improve simultaneously

With NimbleSense™ integrated Closed-Loop Control, Superior Sensor Technology enables designers to achieve higher performance with simpler, more robust system architectures that meet the demands of next-generation medical, industrial, and environmental systems.

Contact our applications engineering team to discuss implementing NimbleSense CLC technology in your next-generation product, leveraging the quantifiable advantages in performance, efficiency, reliability, and time-to-market outlined above.

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