Extech wq5xx water quality meters extech wq530 the extech wq5xx series of water quality meters gives you three models to choose from starting with the wq500 all measure ph mv and temperature you can manually storerecall 150 readings and transfer data directly to a pc via the built in usb interfaceall models also have a built in stirrer with 30 60 and 120 minute timer intervals or continuous operation the wq510 adds conductivity total dissolved solids tds and salinity measurements