FEATURES * 0 to 14 pH x 0.01 pH. * Input Impedance : 10^12 ohms. * pH range Temp. : Not necessary to adjust. * Full optional pH electrode. * Economical cost digital PH meter * General purpose applications. * Easy operation. * PH-211 can ship along with " Case holder " ( Model CH-21, the unit that can hang the PH-211 on the wall ). * Customer also can special order that the PH-211 build in the " 9V DC power adapter socket ", the model no. is PH-211A.