My chargemaster is the European version and the information on the supplied transformer is 9v - 1000mA. The centre pin on the adaptor is the +ve. Outer is -ve
Be careful what transformer you use as a member on here (Viperteks) used a dodgy one and it basically buggered up his chargemaster, readings wandered and became unstable. Changed the power supply to something better and all was well once again
Mark