JPH026355Y2

JPH026355Y2 -

Info

Publication number: JPH026355Y2
Application number: JP4160879U
Authority: JP
Priority date: 1979-03-29
Filing date: 1979-03-29
Publication date: 1990-02-15
Also published as: JPS55141061U

Description

【考案の詳細な説明】本考案は、熱伝導率式ガス分析計に関するもの
である。この種の分析計は、４つのフイラメント
で構成したブリツジに定電流を流すとともに、ブ
リツジの対辺のフイラメントを一組として一方の
組に測定ガスを供給し他方の組にキヤリアガスを
供給するように構成し、ブリツジの不平衡電圧の
大きさからガス濃度の測定等を行うものである。[Detailed Description of the Invention] The present invention relates to a thermal conductivity type gas analyzer. This type of analyzer is configured so that a constant current is passed through a bridge made up of four filaments, and the filaments on the opposite side of the bridge are set as one set, with measurement gas being supplied to one set and carrier gas being supplied to the other set. The gas concentration is then measured based on the magnitude of the unbalanced voltage of the bridge.

フイラメントは常に熱せられた状態で種々のガ
スにさらされているため、その一つが寿命等のた
めに断線する場合が多い。従来装置においては、
フイラメントの断線があつても定電流がブリツジ
に流れるようになつている。このため、電流が他
のフイラメントに集中し、正常なフイラメントも
過熱断線するということが時々あつた。フイラメ
ントは高価なので、経済上問題がある。また、交
換にも多大の時間を要する。 Since the filament is constantly exposed to various gases in a heated state, one of the filaments often breaks due to the end of its life. In conventional equipment,
Even if the filament breaks, a constant current continues to flow through the bridge. For this reason, the current was concentrated on other filaments, and even normal filaments were sometimes overheated and burned out. Since filaments are expensive, there is an economic problem. Also, it takes a lot of time to replace it.

本考案の目的は、フイラメントの断線が他のフ
イラメントの断線をまねかず、断線したフイラメ
ントの交換も容易な熱伝導率式ガス分析計を提供
することにある。 An object of the present invention is to provide a thermal conductivity type gas analyzer in which disconnection of a filament does not lead to disconnection of other filaments, and in which a disconnected filament can be easily replaced.

以下図面を用いて本考案を詳細に説明する。 The present invention will be explained in detail below using the drawings.

図は本考案に係る熱伝導率式ガス分析計の一実
施例を示す構成図である。図において、１は電
源、２はブリツジ、３は電源１とブリツジ２とを
結ぶ電流供給路に配置されたトランジスタ、４は
上記電流供給路に配置された電流検出用抵抗であ
る。ブリツジ２は、フイラメント２Ａ，２Ｂ，２
Ｃ，２Ｄからなる。フイラメント２Ａ，２Ｂはキ
ヤリアガスが供給される比較フイラメント、フイ
ラメント２Ｃ，２Ｄは測定ガスが供給される測定
フイラメントである。５は出力端子がトランジス
タ３のベース端子に接続された演算増幅器、６は
抵抗、７はゼナーダイオードである。抵抗６とゼ
ナーダイオード７の直列回路により得られたゼナ
ー電圧Vdは演算増幅器５の一方の電源電圧とな
つている。８，９は抵抗で、これらは上記ゼナー
電圧Vdを分圧する抵抗回路を構成する。この分
圧電圧Viと、抵抗４に生じた電圧が演算増幅器
５の入力電圧となつている。１０は基準点とトラ
ンジスタ３のベース端子との間に配置されたスイ
ツチ、１１はブリツジ２の不平衡電圧が一定値を
越えると警報信号を発生するとともにスイツチ１
０を閉じる異常検出回路である。この分析計にお
いては、演算増幅器５の最大出力電圧V₀は、 V₀＝（Ｒ＋Rb）・Ｉ＋Ｂただし、Ｒ：抵抗４の抵抗値 Rb：ブリツジ２の合成抵抗Ｉ：ブリツジ２に通常時に流れている定電流値
（Vi／Ｒ）Ｂ：余裕分の電圧（たとえば１〜5V）なる値に選ばれるている。この実施例では、ゼナ
ー電圧VdをほぼV₀と等しく選んでいる。 The figure is a configuration diagram showing an embodiment of a thermal conductivity type gas analyzer according to the present invention. In the figure, 1 is a power supply, 2 is a bridge, 3 is a transistor arranged in a current supply path connecting the power supply 1 and bridge 2, and 4 is a current detection resistor arranged in the current supply path. The bridge 2 has filaments 2A, 2B, 2
Consists of C and 2D. Filaments 2A and 2B are comparison filaments to which carrier gas is supplied, and filaments 2C and 2D are measurement filaments to which measurement gas is supplied. 5 is an operational amplifier whose output terminal is connected to the base terminal of the transistor 3, 6 is a resistor, and 7 is a Zener diode. The zener voltage Vd obtained by the series circuit of the resistor 6 and the zener diode 7 serves as one power supply voltage of the operational amplifier 5. 8 and 9 are resistors, and these constitute a resistance circuit that divides the Zener voltage Vd. This divided voltage Vi and the voltage generated across the resistor 4 serve as the input voltage of the operational amplifier 5. 10 is a switch placed between the reference point and the base terminal of transistor 3; 11 is a switch that generates an alarm signal when the unbalanced voltage of bridge 2 exceeds a certain value;
This is an abnormality detection circuit that closes 0. In this analyzer, the maximum output voltage V ₀ of the operational amplifier 5 is V ₀ = (R+Rb)・I+B where: R: resistance value of resistor 4 Rb: combined resistance of bridge 2 I: voltage flowing through bridge 2 during normal operation The constant current value (Vi/R) B: Voltage with margin (for example, 1 to 5 V) is selected. In this example, the zener voltage Vd is chosen approximately equal to _V0 .

次に上記実施例の動作を説明する。通常の測定
時においては、ブリツジ２に断線がないからブリ
ツジ２の抵抗はRbであり、演算増幅器５の働き
によつてブリツジ２に定電流Ｉが供給されてい
る。ここで、断線が一つのフイラメントに生ずる
と、ブリツジ２の抵抗は２Rbになる。演算増幅
器５はこの抵抗の増大にもかかわらずブリツジ２
に定量流Ｉを供給しようとするが、その出力電圧
の最大値が(1)式で示されるようなものであるた
め、その供給は不可能となる。すなわち、ブリツ
ジ２への供給電流が減少する。これと同時に、フ
イラメントの断線により異常検出回路１１は、一
桁程度大きい不平衡電圧を受けることになり、そ
こから警報信号が発せられ、スイツチ１０も閉じ
られる。これにより、トランジスタ３は遮断さ
れ、ブリツジ２への電流供給は停止される。した
がつて、断線直後においても定電流Ｉがそのまま
一つのフイラメントに流れるようなことがなく、
しかも速やかにブリツジ２への電流供給が停止さ
れるので、他のフイラメントが過熱断線するよう
な事態が生じない。また、この状態においてはブ
リツジ２への電流供給が停止されているので、フ
イラメントの交換作業を迅速かつ容易に行える。 Next, the operation of the above embodiment will be explained. During normal measurement, since there is no disconnection in the bridge 2, the resistance of the bridge 2 is Rb, and a constant current I is supplied to the bridge 2 by the operation of the operational amplifier 5. Here, if a disconnection occurs in one filament, the resistance of the bridge 2 becomes 2Rb. Despite this increased resistance, operational amplifier 5
However, since the maximum value of the output voltage is as shown in equation (1), this supply becomes impossible. That is, the current supplied to the bridge 2 is reduced. At the same time, due to the filament breakage, the abnormality detection circuit 11 receives an unbalanced voltage that is about an order of magnitude larger, and an alarm signal is issued from there, and the switch 10 is also closed. As a result, transistor 3 is cut off and current supply to bridge 2 is stopped. Therefore, even immediately after a wire breakage, the constant current I will not flow directly through one filament.
Moreover, since the current supply to the bridge 2 is immediately stopped, a situation where other filaments are overheated and disconnected does not occur. Furthermore, in this state, the current supply to the bridge 2 is stopped, so that the filament can be replaced quickly and easily.

なお、上記の説明においては、演算増幅器５の
電源電圧をおさえることにより、その出力電圧の
最大値を決めるようにした構成のものを示した
が、出力端子にゼナーダイオードを取り付けても
同様の効果を得ることができる。 In addition, in the above explanation, a configuration is shown in which the maximum value of the output voltage is determined by suppressing the power supply voltage of the operational amplifier 5, but the same result can be obtained even if a Zener diode is attached to the output terminal. effect can be obtained.

以上説明したように、本考案によれば、フイラ
メントの断線が他のフイラメントの断線をまねか
ず、断線したフイラメントの交換も容易な熱伝導
率式ガス分析計を実現できる。 As explained above, according to the present invention, a thermal conductivity type gas analyzer can be realized in which the breakage of a filament does not lead to the breakage of other filaments, and the broken filament can be easily replaced.

[Brief explanation of the drawing]

図は本考案に係る熱伝導率式ガス分析計の一実
施例を示す構成図である。１……電源、２……ブリツジ、３……トランジ
スタ、４……電流検出用抵抗、５……演算増幅
器、７……ゼナーダイオード、６，８，９……抵
抗、１０……スイツチ、１１……異常検出回路。 The figure is a configuration diagram showing an embodiment of a thermal conductivity type gas analyzer according to the present invention. 1... Power supply, 2... Bridge, 3... Transistor, 4... Current detection resistor, 5... Operational amplifier, 7... Zener diode, 6, 8, 9... Resistor, 10... Switch, 11... Abnormality detection circuit.

Claims

[Scope of utility model registration request]

Composed of 4 filaments, combined resistance value Rb
supplying a constant current of current value I to a bridge having
Further, the filaments on opposite sides of the bridge are set as one set, a measurement gas is supplied to one set, a reference gas is supplied to the other set, and the measurement gas is analyzed based on the magnitude of the unbalanced voltage of the bridge. In the rate type gas analyzer, a power supply, a transistor disposed in a current supply path connecting the power supply and the bridge, a current detection resistor having a resistance value R disposed in the current supply path, and a current detection resistor disposed in the current supply path; an operational amplifier that controls the base voltage of the transistor so that the voltage drop is a constant value; a voltage control means that functions to prevent the output voltage of the amplifier from exceeding a predetermined maximum output voltage _V0 ; and abnormality detection means that generates an alarm signal and shuts off the transistor when the balanced voltage exceeds a certain value,
When the margin voltage is B, the maximum output voltage
A thermal conductivity type gas analyzer in which the constant current supply to the bridge is reduced when the filament is broken by selecting the value of V _{0 such that V 0} ₌ (R+Rb)I+B.