CUG30J surrounding rock deformation detector cUG30J surrounding rock deformation detector working principle of the detector using phase-shift laser ranging principle, amplitude modulated laser beam and measuring the phase-modulated light and from the survey line generated a delay, according to the modulated light wavelength conversion this phase delay represents the distance. That is determined by the indirect method of light through the round-trip time required for the survey line. CUG30J surrounding rock deformation detector parameters Supply voltage: 9V Working current: ≤150mA Standby current: ≤40mA measuring distance: 0.5m ~ 30m Measurement error: ± 2mm