www.thedriller.com/articles/86177-multi-probe-field-meter
Multi-probe Field Meter
September 24, 2002

Geotech Environ-mental Equipment Inc.'s YSI 556 MPS simultaneously measures dissolved oxygen, pH, conductivity, temperature, ORP and more. The YSI 556 has been designed to combine the versatility of an easy-to-use, easy-to-read handheld unit with all the functionality of a multiparameter system. Geotech Environmental Equipment Inc.