Meaning
Electrical interference that appears equally and in phase on both signal conductors relative to a local ground. Persistent common mode noise originates from external sources like power lines or switching power supplies and affects the quality of differential measurements in battery management systems. Eliminating this interference is necessary for resolving small voltage changes across individual cells.
Rejection Ratio
Differential amplifiers cancel out signals that are present on both inputs while amplifying the difference between them. The effectiveness of this cancellation is measured by a ratio that decreases at higher frequencies. Superior circuit design maintains high rejection across the entire operating spectrum.
Source Identification
Electromagnetic induction from nearby heavy machinery often couples into unshielded twisted pair cables. Variations in ground potential between different parts of a large battery rack also contribute to these unwanted signals. Proper shielding reduces the magnitude of the induced current by providing a low impedance path to ground.
Grounding the shield at both ends can sometimes introduce more noise if a potential difference exists between the two points.
Filter Integration
Passive components such as chokes or capacitors shunt high frequency interference to ground before it reaches the measurement electronics. These filters must be carefully matched to avoid converting the common signal into a differential one. System accuracy improves when the noise floor is suppressed.
