Feature: Sensors


Figure 1: Wheatstone bridge circuit compensated with 3-wire RTD, used for simulation


Noise reduction in resistive sensors


By Félix Mateo Lázaro, Electronics Engineer


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onnecting a sensor far from the measurement and conditioning circuit introduces small resistances that come from the wiring, but also electrical noise that is picked up by the cables at the circuit’s input. Tis noise depends primarily on the cable length and any surrounding electrical noise.


Traditionally, resistive sensors are mainly connected in a


Wheatstone bridge. Measurements are taken differentially to minimise the noise reading – at least in theory, since the variation in resistance between branches causes some differences in the noise level. Sensors can also be connected with voltage or current excitation. Tese connections alone do not eliminate the electrical noise


16 June 2026 www.electronicsworld.co.uk


picked up by the sensor cables, so appropriate connections and/or noise reduction techniques must be implemented.


Noise reduction Electromagnetic interference, primarily produced by inductive, capacitive and radiative coupling, generates electrical noise that is picked up by the sensor cable, to the point of hindering accurate measurements and even making them impossible. In some cases these cables can exceed 600m in length, making measurements difficult, especially in environments with high levels of electromagnetic interference. One solution is to use twisted-pair and/or shielded cables,


which reduces noise pickup and helps absorb electromagnetic interference. Another solution is to connect low-pass filters to eliminate high-frequency noise, using ceramic capacitors at the input or output of the measurement and conditioning circuit, since the sensor response is oſten slow, especially with temperature sensors. Other applicable techniques, although more expensive, include


sample averaging, which involves taking multiple rapid readings from the sensor and calculating the average digitally to reduce random noise. Digital filters are used to implement low-pass filters, and so on. In cases where these reduction measures are not applicable,


analogue circuits are used to reduce signal noise in the sensor’s conditioning circuit. Tese circuits primarily operate with differential inputs, or by capturing the shape of the noise signal on one wire and subtracting this signal from the excitation circuit. Tis allows the use of relatively fast response sensors, like strain gauges.


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