Takeda Riken Kogyo Kabushiki Kaisha

Masakazu Mitamura

Hikaru Furukawa

Kenji Higuchi

A plurality of metal resistance elements and a metal resistance element for compensation use are formed on a common substrate and placed under the same temperature condition. A reference current is applied to the metal resistance element for compensation use to yield an auxiliary reference voltage. A plurality of switches are individually connected in series to the reference metal resistance elements and the auxiliary reference voltage is provided to the series circuits to selectively control the switches, thereby obtaining various currents.

Variable current source

In an A-D converter of a dual slope system, a digital value set by setting means is provided to switch drive signal generating means to derive therefrom a switch drive signal of a time width corresponding to the digital value, and by the switch drive signal a switch is turned ON, through which a constant voltage is superimposed on an analog input voltage.

Dual slope system A-D converter

Disclosed is an A-D converter in which a voltage to be measured is subjected to first integration for a certain period of time; a reference voltage of the opposite polarity from the voltage to be measured is subjected to second integration until the integrated value obtained by the first integration returns to a predetermined value; measuring clock pulses are counted by a counter circuit in the period of the second integration; and the voltage to be measured is converted by the count value of the counter circuit into a digital value. In the A-D converter, there are provided a variable frequency divider and a memory having stored therein frequency dividing ratio determining signals for changing the frequency dividing ratio of the variable frequency divider. In the period of the second integration, the measuring clock pulses are supplied to the counter circuit through the variable frequency divider and each time the clock pulse is obtained, the frequency dividing ratio determining signals are each detected from the memory and preset in the variable frequency divider. And each time the number of clock pulses supplied to the counter circuit exceeds a certain number, the address of the memory is stepped by one. As a result of this, the frequency dividing ratio of the variable frequency divider sequentially changes, by which is obtained a digital converted value conforming to a non-linear characteristic of the voltage to be measured.

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Gyoda, Japan

Masakazu Mitamura