Wireless temperature cluster
For measuring the vertical temperature gradient cheaply at different stations across about a heactare of land. A heactare is 10000 m^2 or about 100×100 metres. You could use a set of 1-wire temperature sensors in a local cluster. Use a 433MHz radio link and coding similar to this wireless mouse trap and a battery pack to give greater than six month life.
It would need something to collect the information as you don’t want a laptop to be on all of the time. The individual stations could keep transmitting a rolling few days of data or use something like MRTG‘s methods of collating data. Or keep something low power on all of the time that also decodes the protocol and provides a serial interface.
- Transmitter ~$4.20US
- Dallas 18B20 sensor – $2.57US
- Atmel ATTINY or similar – $5NZ
Mechanicals including a waterproof box and antenna, if any, would double the cost.