The utility model relates to a non -contact card communication technology field especially relates to a water gauge that is used for radio frequency circuit of non -contact cartoon letter and containsthis circuit, the radio frequency circuit is including main control chip, EMC filter circuit, radiofrequency signal matching circuit and the radiofrequency signal transmitting circuit of electricityconnection in proper order, main control chip still electricity is connected with crystal oscillator and radiofrequency signal receiving circuit, the utility model is used for data are supplemented with money through the radio -frequency card reading and writing to the water gauge, realize the prepayment function. This circuit adopts the device few, with low costs, and the interference killing feature is strong, and the reliability is high, possesses the ultra -low power consumption characteristic, and the specially adapted adopts battery powered water gauge. Utilize the radio frequency technology, make the water gauge calculate the remaining sum in the water gauge according to the water parameter and the of that month interior real -time earth's core of water consumption, make things convenient for the management of water gauge user and water supply department.