One of my true passions is electrophysiology! I enjoy the engineering and I enjoy the troubleshooting, which often feels like solving a major mystery. Here are some random thoughts and experiences.
60 Hz noise. Wherever we go, we pick up ambient 60 Hz electromagnetic fields (in Europe this would be 50Hz). this is a concern since 60 Hz is frequency employed by the brain when it synchronizes neuronal activity across cells and networks. The main strategies to fight 60 Hz noise are shielding and grounding. Shielding can take different forms but it most often involves a material that conducts (such as aluminum foil, or fabric embedded with metal wires) between the experimental setup and the likely source of the 60Hz field (e.g. power cords etc). Yes - you tin foil hat! Grounding refers to electrically connecting the major pieces of metal (such as cases of devices) to ensure they are on the same potential and thus no current can be introduced by the external 60Hz field. Most devices have a ground port. It is important to connect all ground ports together at one electrical point close to the set-up, essentially giving rise to a star of ground wires. An even better approach is to eliminate the 60Hz at its source such as moving away transformers from the setup or using battery powered equipment. Which takes me to my next point...
Charge and check your batteries! I know of so many devices that do not properly indicate when the battery is getting discharged. You can use a simple volt meter to get an idea if a battery is still good. Just realize that the nominal voltage of a battery such as 9.0V is not necessarily what the charged battery delivers, for example if we are looking at a lithium ion battery, the charged voltage would be less. Google the datasheet of your batteries!
Write down all your settings of your amplifier etc for every single experiment. Most of the devices we use for electrophysiology have some kind of front panel where you can select certain settings such as the gain of the amplifier and the filtering of the signals. Your notes are the only record of these settings. Just because a given knob was "always" in the same position, it just takes one clueless PI wander into the lab and turning the knob to get reminded of how life at the bench felt like. I certianly hope I have never been guilty of this - but who knows!
Lastly - listen to your signals (i.e. feed them into an audio amp). Our ears are the much better real-time signal analyzers than our eyes. By learning what a good recording sounds like, you can very quickly assess the quality of a recording without any analysis. This can then guide your troubleshooting - if you need posthoc data processing to see how noisy your data are, then it is too late to fix the set-up!
OK - enough of all that. Do you enjoy the technical challenges of electrophysiology? I certainly do.