Ungrounded power supplies (two prong) will pass along noise to the part of the SPARKlink Air that records voltage through the builtin voltage sensor. Please use the battery power only if you are recording voltage using the SPARKlink Air built-in voltage sensor. This will result in cleaner data. You can reattach the charger or externally powered USB charger as long as you are not actively collecting data.
You may also see this occur if you are using a laptop computer that is plugged into wall power. If you see this noise in your data, please unplug the computer from the wall while you are collecting data.