64 is used as a buffer the cal signal is applied to the multiplexer 43 and during initialization of the entire system it is selected by microcontroller 45 and used as a known voltage reference signal to calibrate voltage controlled oscillator 80 table 1______________________________________ct logic selected signal______________________________________000 ch 1001 ch 2010 ch 3011 ch 4100 cur101 cal______________________________________ microcontroller 45 is programmed to count the number of interrupts over a predetermined period one second in the preferred embodiment to determine the frequency of the signal sent over line adc and thereby determine the voltage because of its proportionality to the frequency that measured voltage signal which represents the stress being applied against the foundation is compared with a set point which represents the stress applied against the foundation when the foundation is level and is stored in eeprom 46 fig4 d if the measured signal is less than the stored set point then soil shrinkage has occurred and water must be added to the particular zone microprocessor 45 is programmed to send a signal is then sent over one of on off lines 1 through 4 to turn on the appropriate solenoid and water the correct zone referring to fig4 e the solenoid operation will be addressed by way of example if zone 1 is selected microcontroller 45 will set on off line 1 low nor gate 47 is used to prevent the solenoid from being turned on if it is faulty or if there is a system malfunction as long as the system is functioning properly the fault signal generation of the fault signal will be discussed herein remains low and therefore the output of nor gate 47 to transistor q1.