Feature: Sensors


Figure 10: Simulation result of the circuit in Figure 9. The noise-free output is shown in green with the inputs V1 and V2 shown in purple and orange, respectively


the output to keep its values within acceptable limits. Equally, this configuration also produces the expected result with a single power supply. Te only requirement is to keep resistor R1 connected to ground. In this case it is not necessary to add a negative voltage to the output.


Symmetrical Kelvin connection In this case, the Kelvin connection does produce the expected result, compensating for the resistance of the connecting wires without adjustment, and completely cancelling the noise. Te circuit used for the simulation is shown in Figure 9. In this connection, the measurement obtained is directly the voltage across the sensor terminals. It is worth noting that resistors R1 and R2 compensate for


the differences between the two current sources and reduce noise levels in the cables, as they provide ground impedance. However, they introduce output delinearity, so their values should be as high as possible to minimise that.


Careful management Noise reduction in resistive sensor measurement circuits can be problematic in some configurations, whilst complete reduction is achieved in others. Current-driven connections have shown the most problems in various simulations, since they are inherently noisier and require special noise reduction circuitry. Connections with differential inputs, in particular, are not viable without a symmetrical supply, such as the 4-wire Kelvin connection.


22 June 2026 www.electronicsworld.co.uk


In this article I present some symmetrical supply connections that completely cancel noise


Regarding Wheatstone bridge connections with differential


inputs, a 4-wire connection with two opposing sensors offers complete noise cancellation. It should be noted that bridge connections introduce additional delinearisation beyond that of the sensor itself, which can be addressed using the coincidence function linearisation methods. As an alternative to noisy configurations, in this article


I have shown some symmetrical supply connections that completely cancel noise, although some present the problem of compensating for the resistance of the connecting wires. This is not the case with the symmetrical 4-wire Kelvin connection. This problem with connections that don’t compensate for


the resistance of the sensor wires can be solved by establishing a constant total cable resistance using one or two trimmers in series, adjusted to the appropriate value. In some cases, the placement of these trimmers in the circuit is critical, so their most suitable location will be determined on a case-by-case basis.


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