PROBING CORES

摘要

Some time ago, I builtrna handy self-containedrninductance meterrn(What the L is it?. Nutsrn& Volts, August'05). Itrnworks well, but itrnregistered nothingrnwhen I tested somerninductors I'd picked uprnat a hamfest. I set uprnmy old standby — arnparallel capacitor, arnsignal generator, and anrnoscilloscope — and foundrnthese inductors werernextremely lossy. As theirrncores were wound fromrnmetal tape, I wonderedrnif they were designedrnto have square-looprncharacteristics.rnI put together arndevice to displayrntheir behavior.rnHere it is.