sImproved technology for the real-time, continuous monitoring of health of the animals is an important requirement for the animal production industry. We have studied a multimodal sensor consisting of integrated electrical conductivity (EC) and temperature sensors, a wireless unit, and some circuit boards. We measured the information relayed by the integrated sensor located at several positions within the first stomach (known as 'the rumen') in cows. The wireless unit was able to simultaneously monitor the EC and temperature sensors. The results of these tests showed that the developed unit is a useful tool, since the data obtained were reasonable. We then measured the RF field strength as a function of the distance between the wireless unit and the antenna. We calculated the performance that is required in terms of the received power to accurately transmit results from the rumen. We confirmed that the unit could achieve the necessary performance to send data from the rumen to the receiver. We could also find a criterion for the amount of RF power necessary for successful measurements from rumen. (C) 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.