Abstract: It is an object of the present invention to provide an operation control circuit without using a photo-coupler. The operation control circuit controls the operation of an LED in a DC/AC inverter comprising a voltage conversion circuit, a DC/AC conversion circuit for converting output voltage of the voltage conversion circuit to two pieces of AC voltage each with an opposite phase, and an LED which is lit when AC voltage is outputted from the DC/AC conversion circuit. The operation control circuit comprising a rectifier circuit, capacitors connected between the input terminal of the rectifier circuit and the output terminal of the DC/AC conversion circuit, and a comparator circuit connected to the same ground level as the ground level connected to the LED for lighting the LED when voltage V1 outputted from the rectifier circuit is higher than a threshold Vref1.

Abstract: A voltage monitoring device 30 includes an AC input portion 31, a rectifier circuit 32, and a detection circuit 33. The AC input portion 31 receives alternating current output from a DC-AC inverter unit 13. The rectifier circuit 32 rectifies the alternating current received at the AC input portion 31. The rectifier circuit 32 is formed by a full-wave rectifier circuit. The detection circuit 33 detects the output voltage of the rectifier circuit 32. The detection circuit 33 includes a differential amplifier circuit 34. First and second capacitors C1 and C2 are respectively connected to two wires 36a and 36b, which connect the AC input portion 31 and the rectifier circuit 32. The capacitors C1 and C2 are set to have the same capacitance.

Abstract: It is an object of the present invention to provide an operation control circuit without using a photo-coupler. The operation control circuit controls the operation of an LED in a DC/AC inverter comprising a voltage conversion circuit, a DC/AC conversion circuit for converting output voltage of the voltage conversion circuit to two pieces of AC voltage each with an opposite phase, and an LED which is lit when AC voltage is outputted from the DC/AC conversion circuit. The operation control circuit comprising a rectifier circuit, capacitors connected between the input terminal of the rectifier circuit and the output terminal of the DC/AC conversion circuit, and a comparator circuit connected to the same ground level as the ground level connected to the LED for lighting the LED when voltage V1 outputted from the rectifier circuit is higher than a threshold Vref1.

Abstract: A voltage monitoring device 30 includes an AC input portion 31, a rectifier circuit 32, and a detection circuit 33. The AC input portion 31 receives alternating current output from a DC-AC inverter unit 13. The rectifier circuit 32 rectifies the alternating current received at the AC input portion 31. The rectifier circuit 32 is formed by a full-wave rectifier circuit. The detection circuit 33 detects the output voltage of the rectifier circuit 32. The detection circuit 33 includes a differential amplifier circuit 34. First and second capacitors C1 and C2 are respectively connected to two wires 36a and 36b, which connect the AC input portion 31 and the rectifier circuit 32. The capacitors C1 and C2 are set to have the same capacitance.

Abstract: A gas chromatographic system for analyzing gas components includes an analyzer, a constant temperature oven, an analyzer case, an indicator, an integrated sample conditioner, and a coupler. The analyzer includes a sample valve having a detector and a heater built therein and first and second columns wound around the periphery of the sample valve. The constant temperature oven accommodates the analyzer unit therein. The analyzer case accommodates the constant temperature oven. The indicator is protruded from the analyzer case to display analysis processes and results. The integrated sample conditioner provides an optimal condition for analysis. The coupler couples the analyzer unit with the sample conditioner so as to supply a sample gas and one of a carrier gas and a reference gas from the sample conditioner to the analyzer unit.