We produce high qualified geophysical instrument much cheaper. i.e. 1. Automatic resistivity meter (multicahnnel) 2. Manual resistivity meter (twin probe) 3. Sonic wave analyzer (triaxial sonic wave sensor) 4. Digital time delay sonic wave 5. Low frequency accelerometer 6. etc If you are interesting, please email-me for detail to hlkhairy@yahoo.com. Thank you. We give 3 years warranty for whole of our product.