The pH meter appears to be OK, BUT the TDS meter cannot be calibrated or at least there is no instruction on how to perform the procedure. Customer support from the Manufacturer is atrocious. They refuse to acknowledge questions from customers outside North American continent and appear to be deliberately evasive. They do not recognize the Australian Amazon Order number and consequently will not provide support. There is conflicting information given about the need for calibration between the Vivosun website and Amazon / Vivosun Website. Vivosun says that factory calibration lasts 1 year while Amazon / Vivosun says the unit has Upgraded automatic calibration and never requires re-calibration. This is remarkable if true, as other meters costing 10 X the price still need to be regularly re-calibrated.