Common Causes of Poor EMG/EEG Signal Quality (and How to Fix Them)
When a trace looks noisy, flat, or unreliable, the electrodes are the first place to check — before assuming it's an equipment fault. Here are the most common causes we hear about from clinics, roughly in the order worth checking.
High Electrode Impedance
The single most common cause of a noisy or unstable trace. Skin oils, dead skin, and hair all raise impedance at the electrode site. Proper skin prep before electrode placement — and the right conductive gel for the electrode type you're using — makes the biggest difference. See Conductive Gels & Pastes Compared for which gel or paste fits which electrode.
Worn or Degraded Reusable Electrodes
Reusable disc, ring, and bar electrodes lose surface plating over repeated cleaning cycles, which raises impedance even with good skin prep. If a specific reusable electrode consistently underperforms compared to others in the same set, it's usually due for replacement rather than a sign of a bigger problem. See our sterile vs. non-sterile electrode guide for what "reusable" actually requires between uses.
Loose or Damaged Connections
Intermittent noise or dropout during a procedure often traces back to a worn leadwire, a loose touch-proof connector, or a damaged extension cable rather than the electrode itself. Check electrode extensions and adapters for wear before assuming the electrode has failed.
Poor Ground Electrode Placement
A ground electrode placed too far from the recording site, or on a poorly prepped area, increases common-mode noise across the whole recording. See reusable ground electrodes and disposable ground reference electrodes.
Environmental Interference
60 Hz line noise from nearby equipment, fluorescent lighting, or unshielded cabling can show up as regular, rhythmic noise that isn't coming from the electrode setup at all. If impedance checks out and the trace is still noisy, this is worth ruling out before troubleshooting the electrodes further.