Abstract: The present invention provides a heater temperature control circuit including a heater and a control circuit that controls a temperature of the heater, wherein the control circuit includes a bridge circuit in which a first circuit and a second circuit are connected in parallel, and an operational amplifier connected to the bridge circuit, wherein in the first circuit, the heater and a resistor are connected in series, and a midpoint of the first circuit is connected to one input portion of the operational amplifier, and an output value Vout from the second circuit is input to the other input portion of the operational amplifier, the output value Vout being obtained by multiplying a division ratio of a target resistance value Rh of the heater and a resistance value R1 of the resistor with a reference voltage Vref of the bridge circuit.

Abstract: The present invention provides a heater temperature control circuit including a heater and a control circuit that controls a temperature of the heater, wherein the control circuit includes a bridge circuit in which a first circuit and a second circuit are connected in parallel, and an operational amplifier connected to the bridge circuit, wherein in the first circuit, the heater and a resistor are connected in series, and a midpoint of the first circuit is connected to one input portion of the operational amplifier, and an output value Vout from the second circuit is input to the other input portion of the operational amplifier, the output value Vout being obtained by multiplying a division ratio of a target resistance value Rh of the heater and a resistance value R1 of the resistor with a reference voltage Vref of the bridge circuit.

Abstract: In order to provide a hydrogen sensor for measuring a hydrogen concentration with high sensitivity and excellent mass-productivity, the hydrogen sensor includes: at least a first quartz vibrator and a second quartz vibrator formed in a quartz plate; a hydrogen reaction catalytic layer including a platinum film of platinum black formed on both sides of the first quartz vibrator; and a hydrogen non-reactive layer formed in the second quartz vibrator, wherein a hydrogen concentration is measured by measuring a temperature of the first quartz vibrator increasing by heat of combustion caused by oxidization of hydrogen by the hydrogen reaction catalytic layer as a change of a natural frequency of the first quartz vibrator with respect to a natural frequency of the second quartz vibrator.

Abstract: In order to provide a hydrogen sensor for measuring a hydrogen concentration with high sensitivity and excellent mass-productivity, the hydrogen sensor includes: at least a first quartz vibrator and a second quartz vibrator formed in a quartz plate; a hydrogen reaction catalytic layer including a platinum film of platinum black formed on both sides of the first quartz vibrator; and a hydrogen non-reactive layer formed in the second quartz vibrator, wherein a hydrogen concentration is measured by measuring a temperature of the first quartz vibrator increasing by heat of combustion caused by oxidization of hydrogen by the hydrogen reaction catalytic layer as a change of a natural frequency of the first quartz vibrator with respect to a natural frequency of the second quartz vibrator.