Gossen-Metrawatt-M507A-Metraline-Z-check-VDE-Tester-Gossen-Metrawatt-M507A-The-Gossen-Metrawatt-Metraline-Z-check-M507A-loop-resistance-measuring-instrument-is-part-of-the-Metraline-range-which-has-the-design-philosophy-of-concentrating-on-measuring-one-parameter-&-doing-it-well-This-leads-to-simplicity-of-design-&-speed-of-use-In-this-case-the-parameter-is-impedance-including-fault-loop-impedance-with-short-circuit-current-fault-loop-impedance-with-short-circuit-current-without-tripp