This invention discloses a multi-channel signal conditioning circuit designed for simultaneous measurement of resistance, capacitance, and inductance from multiple sensor types. It uses bidirectional current excitation, programmable current sources, and phase-sensitive synchronous rectification (PSSR) to ensure accurate, low-noise, and wide-range sensing. The circuit eliminates traditional errors caused by front-end multiplexers by switching at a later stage, after signal amplification and filtering, and provides a clean DC voltage output ready for microcontroller interface. Applications span across healthcare, environment, and industrial domains.
Figure 1. Block diagram of the proposed design
Existing multi-sensor readout circuits suffer from noise, limited dynamic range, high component count, and switching errors due to front-end multiplexers. They also require complex digital control and are not optimized for low-power or portable systems. There is a need for a simplified, robust, and accurate multi-channel signal conditioning system that supports resistive, capacitive, and inductive sensing with minimal control overhead and improved resolution.
- Wide Dynamic Range: The circuit supports resistive measurements from 100 Ω to 4 MΩ and capacitive sensing from 200 pF to 1 µF (extendable up to 10 mF with programmable current sources).
- Post-Amplification Switching: Unlike traditional designs, the switching/multiplexing is done after amplification and band-pass filtering, which minimizes sensor crosstalk and signal degradation.
- Phase-Sensitive Synchronous Rectification (PSSR): The process utilizes phase-locked detection and low-pass filtering to generate a stable DC signal output, reducing noise and improving signal fidelity.
- Programmable Measurement Configuration: This offers configurable current sources (1 µA to 10 mA), gain (1–1000), and excitation frequency (100 Hz to 1 kHz), making the system highly adaptable.
- Multi-Sensor Support: It enables simultaneous and switchable measurements for various sensor types—resistive, capacitive, inductive—across dual channels using time-multiplexing.
A working prototype of the multi-channel signal conditioning circuit was developed and verified through simulation using TINA-TI software and practical circuit implementation. The system includes programmable current sources (1 µA to 10 mA), dual-channel half-bridge configuration, instrumentation amplifiers, and band-pass filters. It performs accurate measurements of small resistance or capacitance changes using PSSR. The output is converted into a pure DC voltage through a low-pass filter and fed into a microcontroller with on-chip ADC. The hardware supports a plug-and-play DB-9 connector interface and is scalable up to 8 channels, suitable for integration with external electronics for smart sensing applications.
A fully developed and simulated circuit supports simultaneous R, L, and C measurements with programmable current (1 μA to 10 mA) and broad sensor range (100 Ω to 4 MΩ, 200 pF to 10 mF). It’s optimized for low power, high resolution, and microcontroller interfacing.
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This technology can play a critical role in developing low-cost, portable, and accurate sensing solutions for applications such as medical diagnostics, environmental monitoring, soil health analysis, and chemical sensing. It reduces circuit complexity and power consumption, making it ideal for rural healthcare, precision agriculture, and wearable biosensors, thereby expanding access to essential diagnostics in resource-constrained environments.
- Intelligent irrigation systems with real-time data collection: Soil moisture, salinity, and nutrient sensing using resistive/capacitive sensors
- Explosive detection systems using resistive or capacitive changes: Gas, humidity, and chemical sensors
- Bio-sensing: Sweat analysis, glucose monitoring, where multi-sensor integration is needed
- Simultaneous sensing of multiple parameters: Temperature, humidity, particulate matter
- Embedded sensor circuits in packaging: To detect spoilage, tampering, or storage conditions
Geography of IP
Type of IP
4202/MUM/2015
387955