I am currently having a lot of trouble with noise being picked up by load cells.
The strain gauges on the load cell are configured in a full-bridge pattern. In a noiseless environment (ie far away from any micro/power supply lines) the system performs admirably.
However, the four wires that come from the load cell I believe are picking up noise. If these wires lie close (within 75mm) of a USB cable they pick up noise, or there is a WIFI/3G module nearby the wires also pick-up the EMI noise.
In an attempt to mitigate these problems we have twisted the wires coming from the load cell to reduce the inductance loop and therefore reduce the noise problem. This has no helped.
Therefore we are now looking into types of shielding, and thus brings me to the question.
How effective would copper (or aluminium) tape be if I were to wrap it wrap the end of the load cell, all the way along the wires and over the PCB that has the ADC chip mounted on it?
Before you ask about is it coming from other noise sources, I have eliminated the power supply as the noise as I am using a heavily filtered vref design specifically for the low noise applications.
The signal level that exists between the S+ and S- lines is at a maximum 3mV therefore any noise very quickly ruins the signal.
When I twisted the wires coming from the load cell I twisted all four at once and not as twisted pairs, would this have any impact on the result?