Notes on the location of electrical lines, radio transmission towers, known metallic objects, topography, and weather should be collected at each field site, as should decisions about the QA/QC procedures above. It is important to check and record: battery voltages, x–y–z positions of the electrodes, how their position was determined (meter tape, GPS, laser level, etc.), and how the electrodes were deployed and/or built. The integrity of multi-core cables should be assessed, particularly around individual electrode takeouts that are most prone to damage during use. For cross-well measurements, information on well construction (casing length, total depth, borehole integrity, presence of monitoring equipment, etc.) should be known prior to installing cables and injecting current. Some commercially available systems provide a test resistor to verify the correct operation of the instrument. Results of this test, if performed, should be recorded. Although outside the scope of this book, safety is an important consideration when dealing with any electrical instrumentation, and equipment users should develop protocols to ensure that no one touches energized electrodes during data collection. These issues do not prevent collection of quality data, but should be recorded and considered when evaluating data quality.