Critical Evaluation of the Pulsed-Current Resistance Meter for Detection of Decay in Wood

An evaluation of a pulsed-eurrent resistance meter ("Shigometer®", Model No. 7950) for facilitating detection of decay was performed on wood blocks of giant sequoia heartwood and of white fir sapwood. As decay progressed over a 12-week incubation period, a trend of lower meter readings was obtained, confirming reported field measurements of other workers. Variability in meter readings in situations where the range in resistance readings between sound and decayed wood is narrow (e.g., giant sequoia heartwood) and apparent inability of the meter to make readings necessary to diagnose dec.ay at MCs common to wood in service without ground or water contact are considered to be the major limitations of the instrument. Shortcomings of the instrument, along with suggestions for improvement in meter design, are discussed. PREVIOUS REPORTS have shown that the pulsed­ current resistance meter, (manufactured by Northeast Electronics, Concord, New Hampshire; commonly referred to as the "Shigometer®"), facilitated detection of decay in several tree species (6, 9, 11, 12, 13). The meter has also been reported to provide information necessary for assessing levels of stress and vigor in some hardwood tree species (16). The degree of resistance to a pulsed electric current in progressive stages of decay and discoloration reportedly (2, 13) is