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1. INTRODUCTION
Thank you for choosing the HYDROS 21 Water Depth, Temperature, and Electrical
Conductivity (EC) sensor from METER Group.
The HYDROS 21 (CTD) is designed for groundwater monitoring wells or piezometers, surface
water monitoring, and wetland monitoring. The sensor cable is vented to remove the effects
of barometric pressure changes. The sensor also features a precision thermistor to measure
temperature. The integrated 4-probe electrical conductivity transducer accurately senses EC
up to 120 mS/cm.
Prior to use, verify the sensor arrived in good condition.