Abstract: Disclosed is a gas flow path switching unit including a gas passage section with a target gas passage for allowing said target gas to pass therethrough. The target gas passage includes a main passage having a proximal end serving as said gas inlet and a number n of branch passages each provided with a respective gas outlet at a terminal end thereof. The branch passages are formed by repeating two or more times a branching process of branching said main passage into two sub passages at a branch point at a distal end of said main passage and further branching at least one of said sub passages into two sub-sub passages at a branch point defined by a distal end of said sub passage. The target gas passage also includes at least a number n of switching-gas supply passages connected to respective intermediate positions of said n branch passages.

Abstract: Disclosed is a gas chromatograph, which comprises a column oven which has a ventilation door disposed in an upper portion thereof and a hydrogen gas sensor installed in an upper region of an internal space thereof. Based on a detection signal from the hydrogen gas sensor, a control section determines a concentration of hydrogen gas contained in a gas within the column oven. If the concentration is equal to or greater than a given threshold value, the control section operates to open the ventilation door while cutting off current to be supplied to a heater, and closing a valve to stop supply of hydrogen gas. Thus, in the event of leakage of hydrogen gas, hydrogen gas accumulated within the column oven can be quickly released outside the column oven to avoid a risk of inflaming.

Abstract: Disclosed is a gas flow path switching unit including a gas passage section with a target gas passage for allowing said target gas to pass therethrough. The target gas passage includes a main passage having a proximal end serving as said gas inlet and a number n of branch passages each provided with a respective gas outlet at a terminal end thereof. The branch passages are formed by repeating two or more times a branching process of branching said main passage into two sub passages at a branch point at a distal end of said main passage and further branching at least one of said sub passages into two sub-sub passages at a branch point defined by a distal end of said sub passage. The target gas passage also includes at least a number n of switching-gas supply passages connected to respective intermediate positions of said n branch passages.

Abstract: A gas chromatograph set of the present invention comprises a plurality of gas chromatographs and a flow passage assembly. Each of the gas chromatographs includes a column for separating sample-components, a carrier gas supply unit for supplying a carrier gas to the column and a detector for detecting eluted components from the column. The carrier gas supply unit comprises a carrier gas passage, and a flow controller unit for controlling a flow-rate that is connected to the carrier gas passage. The flow passage assembly comprises a metal plate inside which the carrier gas passages of the gas chromatographs are formed.

Abstract: A gas chromatograph set of the present invention comprises a plurality of gas chromatographs and a flow passage assembly. Each of the gas chromatographs includes a column for separating sample-components, a carrier gas supply unit for supplying a carrier gas to the column and a detector for detecting eluted components from the column. The carrier gas supply unit comprises a carrier gas passage, and a flow controller unit for controlling a flow-rate that is connected to the carrier gas passage. The flow passage assembly comprises a commonly-used metal plate inside which the carrier gas passages of the gas chromatographs are formed.

Abstract: A gas chromatograph is with a fluid control assembly for controlling flow and pressure of gas. The fluid control assembly includes a flow path, a control valve situated in the flow path and being capable of adjusting an opening degree thereof, a flow resistance provided in the flow path at a downstream side of the control valve, a differential pressure detecting device for detecting a differential pressure between two ends of the flow resistance, and a pressure detecting device for detecting pressure on an upstream side or a downstream side of the flow resistance. A control device carries out a predetermined calculation based on signals from the differential pressure detecting device and the pressure detecting device for controlling the opening degree of the control valve based on a result of the calculation. Thus, the fluid control assembly is applicable to either flow control or pressure control.

Abstract: In a method of analyzing a sample, an internal pressure of a sample chamber is maintained at a predetermined level through a control valve. When the sample is injected into the sample chamber, the control valve is held at an opening degree before the sample is injected into the sample chamber for a predetermined period of time. Thus, a substantial amount of the sample injected to the sample chamber can be sent to a detector without loosing through the control valve.

Abstract: A gas chromatograph includes a control unit. The control unit normally operates such that a pressure sensor monitors an internal pressure of a sample vaporization chamber, and gas is discharged through a split path based on the internal pressure, thereby maintaining the internal pressure constant. When a large quantity of a sample is quickly injected and the internal pressure of the sample vaporization chamber exceeds a preset threshold value, the control unit shuts off for a predetermined time a control valve to lock at an opening degree right before the shut-off. Therefore, it is possible to minimize an amount of the sample released through the control valve.

Abstract: A bridge circuit serving as a detector of a physical variable such as pressure has four resistors forming a wheatstone bridge, one of the resistors changing resistance according to variations in the physical variable to be measured. Voltage difference between a mutually opposite pair of junctions of the four resistors is measured by one circuit and that between the other mutually opposite pair of junctions is measured by another circuit. The effect of temperature variation is calculated from these measured values to reduce the drift in the value of pressure calculated from the voltage imbalance of the wheatstone bridge.

Abstract: A gas chromatograph has a pressure sensor measuring a pressure in a sample introduction part, a flow control valve controlling carrier gas flow rate, a flow sensor measuring a flow rate of the carrier gas, a split flow path exhausting part of a carrier gas and sample from the introduction part, an exhaust valve placed in the sprit flow path, and a monitor screen. The controller controls the flow control valve to flow the carrier gas at the designated flow rate into the introduction part, reads an output of the pressure sensor after making the exhaust valve fully open, calculates a flow path resistance of the filter by using an output of the pressure sensor and a flow path resistance of the chromatographic column, and controls the monitor screen to display an indication for exchanging the filter when the calculated resistance reaches the preset value corresponding to a state in which the filter is stuffed.

Abstract: A bridge circuit serving as a detector of a physical variable such as pressure has four resistors forming a wheatstone bridge, one of the resistors changing resistance according to variations in the physical variable to be measured. Voltage difference between a mutually opposite pair of junctions of the four resistors is measured by one circuit and that between the other mutually opposite pair of junctions is measured by another circuit. The effect of temperature variation is calculated from these measured values to reduce the drift in the value of pressure calculated from the voltage imbalance of the wheatstone bridge.