The RFID device adopts RF signals to transmit data, but the signals are easily interfered by a wet environment within the metal fences. The parlor is such an environment. However, to monitor the health of a cow, a low-frequency (LF) RFID reader is utilized to identify the tags that are tied on the ear of the cow. The selected reader herein is the ROMAG G90A with 125 kHz frequency. The environment has a weaker effect on the low-frequency reader. However, the disadvantage of such a reader is that it has a shorter sensing distance. A reader with a longer sensing distance requires a much higher transmission power. The sensing distance of the reader herein is between 90 cm and 130 cm. The width of the path of the animals through the parlor is around 100 cm. Therefore, two RFID readers are set up on both sides of the path to reduce the failure rate in the reading of tags.