Geonics - Model EM61S - Submersible Metal Detectors
From Metal Detectors
For operation in marine environments, the EM61S is a completely submersible coil and cable system capable of submersion to depths of more than 60 metres. Available as an attachment to the standard EM61-MK2 (or EM61), the EM61S includes a single coincident transmitter/receiver coil, with cable, only; without a second receiver coil, as is included with the standard EM61-MK2 (or EM61), the calculation of differential data is not available.
Most commonly, the EM61S is secured to a submersible platform that is positioned and operated at the bed plane. On occasion, environmental or other restrictions will require that the platform is removed some distance from the bed plane. In relatively shallow water environments, an alternate configuration of the EM61S combines a large (10 x 10 m) transmitter loop on the surface of the water, with a submersible receiver coil suspended at the required offset distance.
Importantly, the EM61S, in all configurations, has shown to be equally applicable in both freshwater and saltwater environments.
To increase the depth at which any target is detectable, the high power (HP) modification provides an eight-fold increase in the amount of signal received by a standard transmitter coil resulting in significant improvements in the signal-to-noise ratio. Relative to the standard EM61-MK2A, the depth of detection for any target will increase between 45% and 80%, depending on target characteristics - (see sidebar Figure; click to enlarge).