EARTH MAGNETISM COMPENSATING POWER SUPPLY

PROBLEM TO BE SOLVED: To reduce cost for a power supply part and to shorten a time for setting a magnetic field by integrating a direct-current power supply supplying a current to earth magnetism compensating coils of three systems, a circuit controlling the current and a circuit varying reference voltage applied to the circuit. SOLUTION: A power supply is actuated in a power supply body by turning a main power supply switch. A current which is made to flow to coils of three systems is set by a rotary switch 20. Polarity of each of currents which are made to flow to the coils of the three systems is set by a switch 21. In short, when the switch 21 is OFF, currents are made to flow from terminals 25, 27 and 29 to terminals 26, 28 and 30, respectively, and when the switch is ON, currents are made to flow from the terminals 26, 28 and 30 to the terminals 25, 27 and 29, respectively. A current value which is made to flow to the coil is measured with an ampere meter 22. A switch 23 decides which current value of coil should be measured with the ampere meter 22, and four modes of verticality, north and south, east and west and automatic scanning mode are selected.