... CPU continuously monitors and displays thebattery level, When the battery is running out of power, Thebattery icon will disappear ... Electrode (Only for SELON 221), pHStandard Buffer, Temperature Probe, 9V BatterySPECIFICATIONS: Model SELON220 SELON221 pH Range -2.00~16.00pH ... Date/Time stamping Output USB communication interface Power Requirements 9V/800mA battery Dimensions 185(L)×88(W)×32(H)mm ...