JPH05164721A - Humidity detecting circuit - Google Patents
Humidity detecting circuitInfo
- Publication number
- JPH05164721A JPH05164721A JP3351714A JP35171491A JPH05164721A JP H05164721 A JPH05164721 A JP H05164721A JP 3351714 A JP3351714 A JP 3351714A JP 35171491 A JP35171491 A JP 35171491A JP H05164721 A JPH05164721 A JP H05164721A
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- resistor
- temperature
- series
- bridge circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は湿度検出回路に係り、特
にたとえば電子レンジなどの加熱調理装置において誘電
加熱される被調理物の仕上りの程度を検出するための湿
度検出回路の改良に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity detecting circuit, and more particularly to an improvement of a humidity detecting circuit for detecting the degree of finishing of an object to be cooked by dielectric heating in a cooking apparatus such as a microwave oven. is there.
【０００２】[0002]
【従来の技術】従来の電子レンジなどの加熱調理装置に
おいては、絶体湿度検知器等を調理庫の排気口付近に設
置し被調理物が加熱されることによって発生する水蒸気
を該検知器で検知して被調理物の仕上り制御を行なう公
知の手段が用いられている。2. Description of the Related Art In a conventional cooking device such as a microwave oven, an absolute humidity detector or the like is installed in the vicinity of an exhaust port of a cooking cabinet to generate water vapor generated by heating an object to be cooked. Known means for detecting and controlling the finish of the food to be cooked is used.
【０００３】このような検知器の感温素子として、例え
ば白金抵抗体のように正の温度特性を有する素子が用い
られた場合の従来の湿度検知回路の一例を図４に示す。
同図に示すように、同回路は二つの感温素子Ｒｓ，Ｒｒ
を具備しており、第一の感温素子Ｒｓを雰囲気に暴露、
第二の感温素子Ｒｒを密閉状態にし、前記第一、第二の
感温素子Ｒｓ，Ｒｒを略同一温度に自己加熱し、雰囲気
中の湿度変化による熱伝達係数の変化を第一の感温素子
Ｒｓの抵抗値の変化で検出し、雰囲気の温度変化を第二
の感温素子Ｒｒで補償しつつ、絶対湿度を検出する湿度
検知器を構成している。また、該湿度検知器を動作させ
るための電源電圧Ｅｏの電源を設ける一方、前記二つの
感温素子Ｒｓ，Ｒｒの抵抗比を検出するためにブリッジ
回路を構成する第一、第二の二つの抵抗体Ｒ１，Ｒ２
と、前記感温素子Ｒｓ，Ｒｒの抵抗比を電圧変換する後
述の電圧変換回路を具備し、前記二つの感温素子Ｒｓ，
Ｒｒを直列に接続し、一方の端子を電源電圧Ｅｏの電源
に接続、他方の端子をグランド側に接続し、さらに二つ
の感温素子Ｒｓ，Ｒｒに並列に第一、第二の抵抗体Ｒ
１，Ｒ２を直列に接続することによりブリッジ回路を構
成し、第一、第二の感温素子Ｒｓ，Ｒｒの接続点と、第
一、第二の抵抗体Ｒ１，Ｒ２の接続点を該電圧変換回路
に接続し該電圧変換回路の出力より絶対湿度量を検出す
るものである。FIG. 4 shows an example of a conventional humidity detecting circuit when an element having a positive temperature characteristic such as a platinum resistor is used as a temperature sensitive element of such a detector.
As shown in the figure, the circuit includes two temperature sensitive elements Rs and Rr.
The first temperature sensitive element Rs is exposed to the atmosphere,
The second temperature-sensitive element Rr is hermetically sealed, the first and second temperature-sensitive elements Rs, Rr are self-heated to substantially the same temperature, and a change in the heat transfer coefficient due to a change in humidity in the atmosphere is first sensed. A humidity detector that detects the absolute humidity while detecting the change in the resistance value of the temperature element Rs and compensating the temperature change of the atmosphere with the second temperature sensitive element Rr is configured. Further, while a power supply of a power supply voltage Eo for operating the humidity detector is provided, first and second two which form a bridge circuit for detecting the resistance ratio of the two temperature sensing elements Rs and Rr are provided. Resistors R1, R2
And a voltage conversion circuit, which will be described later, for converting the resistance ratio of the temperature sensitive elements Rs and Rr into a voltage.
Rr is connected in series, one terminal is connected to the power supply of the power supply voltage Eo, the other terminal is connected to the ground side, and the first and second resistors R are connected in parallel to the two temperature sensing elements Rs and Rr.
A bridge circuit is configured by connecting 1 and R2 in series, and the connection point of the first and second temperature sensitive elements Rs and Rr and the connection point of the first and second resistors R1 and R2 are connected to the voltage. It is connected to a conversion circuit and detects the absolute humidity amount from the output of the voltage conversion circuit.
【０００４】なおここで二つの感温素子Ｒｓ，Ｒｒの中
点は演算増幅器ＯＰの反転入力端子にＯＰの入力抵抗Ｒ
ｃを介して接続されており、一方、二つの抵抗体Ｒ１，
Ｒ２の中点は演算増幅器ＯＰの非反転入力端子に接続さ
れている。また演算増幅器ＯＰとＯＰの入力抵抗Ｒｃの
中間点と演算増幅器ＯＰの出力端子との間にＯＰの負帰
還抵抗Ｒｆが接続されている。これら、ＯＰ，Ｒｃ，Ｒ
ｆによって電圧変換回路が構成されているものである。
このような構成におけるＯＰの出力電圧をＶout で表わ
すと、次の（１）式で表わされる。 但しＡｖは増幅率で、Ａｖ＝Ｒｆ／Ｒｃで表わされる。Here, the midpoint between the two temperature sensitive elements Rs and Rr is connected to the inverting input terminal of the operational amplifier OP by the input resistance R of OP.
connected via c, while two resistors R1,
The middle point of R2 is connected to the non-inverting input terminal of the operational amplifier OP. Further, a negative feedback resistor Rf of OP is connected between the midpoint of the operational amplifier OP and the input resistance Rc of OP and the output terminal of the operational amplifier OP. OP, Rc, R
The voltage conversion circuit is configured by f.
When the output voltage of the OP in such a configuration is represented by Vout, it is represented by the following equation (1). However, Av is an amplification factor and is represented by Av = Rf / Rc.
【０００５】また、検知器の感温素子として、例えばサ
ーミスタのように負の温度特性を有する素子が用いられ
た場合の従来の温度検出回路の一例を図５に示す。同図
に見られるように、サーミスタなどの負の特性を持つ素
子は高温になると抵抗値が下り、定電圧電源で駆動した
場合自己加熱温度が雰囲気温度の上昇とともに急激に上
昇し最悪の場合、素子破壊につながるため、通常は電源
との間に電流制限抵抗Ｒｄを挿入するものである。その
他の構成については概ね前記の白金抵抗体の場合と同様
である。即ち、二つの感温素子Ｒｓ，Ｒｒを具備してお
り、第一の感温素子Ｒｓを雰囲気に暴露、第二の感温素
子Ｒｒを密閉状態にし、前記第一、第二の感温素子Ｒ
ｓ，Ｒｒを略同一温度に自己加熱し、雰囲気中の湿度変
化による熱伝達係数の変化を第一の感温素子Ｒｓの抵抗
値の変化で検出し、雰囲気の温度変化を第二の感温素子
Ｒｒで補償しつつ、絶対湿度を検出する湿度検知器を構
成している。また、該湿度検知器を動作させるための電
源電圧Ｅｏの電源を設ける一方、前記二つの感温素子Ｒ
ｓ，Ｒｒの抵抗比を検出するためにブリッジ回路を構成
する第一、第二の二つの抵抗体Ｒ１，Ｒ２と、前記湿度
検知器に流れる電流値を制限する電流制限抵抗体Ｒｄ
と、前記感温素子Ｒｓ，Ｒｒの抵抗比を電圧変換する後
述の電圧変換回路を具備し、前記二つの感温素子Ｒｓ，
Ｒｒを直列に接続し、一方の端子を電流制限抵抗体Ｒｄ
に接続、他方の端子をグランド側に接続し、さらに二つ
の感温素子Ｒｓ，Ｒｒに並列に第一、第二の抵抗体Ｒ
１，Ｒ２を直列に接続し、いわゆるブリッジ回路を構成
し、前記電流制限抵抗体Ｒｄの他方の端子を電源電圧Ｅ
ｏの電源に接続し、第一、第二の感温素子Ｒｓ，Ｒｒの
接続点と、第一、第二の抵抗体Ｒ１，Ｒ２の接続点を該
電圧変換回路に接続し、該電圧変換回路の出力と第一、
第二の抵抗体Ｒ１，Ｒ２の中点電圧ＶTとを演算処理す
る演算処理部３と該演算処理部３の出力により絶対湿度
量を検出するものである。FIG. 5 shows an example of a conventional temperature detecting circuit in the case where an element having a negative temperature characteristic such as a thermistor is used as the temperature sensitive element of the detector. As can be seen in the figure, the resistance of an element with negative characteristics such as a thermistor decreases at high temperature, and when driven by a constant voltage power supply, the self-heating temperature rises sharply with increasing ambient temperature, and in the worst case, The current limiting resistor Rd is usually inserted between the power source and the power source because it leads to element destruction. Other configurations are substantially the same as those of the platinum resistor described above. That is, it is equipped with two temperature sensitive elements Rs and Rr, the first temperature sensitive element Rs is exposed to the atmosphere, the second temperature sensitive element Rr is sealed, and the first and second temperature sensitive elements are arranged. R
s and Rr are self-heated to approximately the same temperature, and a change in the heat transfer coefficient due to a change in humidity in the atmosphere is detected by a change in the resistance value of the first temperature sensing element Rs, and a temperature change in the atmosphere is detected as a second temperature sensing A humidity detector that detects the absolute humidity while compensating with the element Rr is configured. Further, while a power source of a power source voltage Eo for operating the humidity detector is provided, the two temperature sensing elements R are provided.
First and second two resistors R1 and R2 that form a bridge circuit for detecting the resistance ratio of s and Rr, and a current limiting resistor Rd that limits the current value flowing in the humidity detector.
And a voltage conversion circuit, which will be described later, for converting the resistance ratio of the temperature sensitive elements Rs and Rr into a voltage.
Rr is connected in series and one terminal is a current limiting resistor Rd
, The other terminal is connected to the ground side, and the first and second resistors Rs and Rr are connected in parallel with each other.
1, R2 are connected in series to form a so-called bridge circuit, and the other terminal of the current limiting resistor Rd is connected to the power supply voltage E.
connected to the power source of 0, the connection point of the first and second temperature sensitive elements Rs and Rr and the connection point of the first and second resistors R1 and R2 to the voltage conversion circuit, and the voltage conversion Circuit output and first,
An arithmetic processing unit 3 for arithmetically processing the midpoint voltage V T of the second resistors R1 and R2 and an output of the arithmetic processing unit 3 detect the absolute humidity amount.
【０００６】なお電圧変換回路についても概ね前記の白
金抵抗体の場合と同様、二つの感温素子Ｒｓ，Ｒｒの中
点が演算増幅器ＯＰの反転入力端子に入力抵抗Ｒｃを介
して接続され、一方二つの抵抗体Ｒ１，Ｒ２の中点が演
算増幅器ＯＰの非反転入力端子に接続されており、また
演算増幅器ＯＰと入力抵抗Ｒｃとの中間点と演算増幅器
ＯＰの出力端子との間にＯＰ負帰還抵抗Ｒｆが接続され
て、電圧変換回路が構成されているが、さりにこの電圧
変換回路の出力であるＯＰの出力電圧Ｖout と二つの抵
抗体Ｒ１，Ｒ２の中点電圧ＶT とを演算処理部３により
演算処理して得られた出力Ｖout ／ＶT の演算補正を行
ない絶対湿度出力としている。なお、Ｖｆはブリッジ回
路電圧である。Also in the voltage conversion circuit, the midpoint of the two temperature sensitive elements Rs and Rr is connected to the inverting input terminal of the operational amplifier OP through the input resistor Rc, as in the case of the platinum resistor described above, and The middle point of the two resistors R1 and R2 is connected to the non-inverting input terminal of the operational amplifier OP, and the OP negative terminal is provided between the intermediate point between the operational amplifier OP and the input resistor Rc and the output terminal of the operational amplifier OP. The feedback resistor Rf is connected to form a voltage conversion circuit, and the output voltage Vout of OP which is the output of this voltage conversion circuit and the midpoint voltage V T of the two resistors R1 and R2 are calculated. The output Vout / V T obtained by the arithmetic processing by the processing unit 3 is subjected to arithmetic correction to obtain an absolute humidity output. Note that Vf is a bridge circuit voltage.
【０００７】このような構成におけるＯＰの出力電圧Ｖ
out は次の（２）の式で表わされる。 但しＡｖは前述の増幅率で、Ａｖ＝Ｒｆ／Ｒｃ、 Ｖｆはブリッジ回路電圧で、Ｖｆ＝Ｅｏ×Ｚｓ／（Ｚｓ
＋Ｒｄ） Ｚｓはブリッジ回路の合成抵抗値で、Ｚｓ＝（Ｒｓ＋Ｒ
ｒ）×（Ｒ１＋Ｒ２）／（Ｒｓ＋Ｒｒ＋Ｒ１＋Ｒ２）で
ある。しかしながら（２）式はＶｆが温度変化によるサ
ーミスタ抵抗値Ｒｓ，Ｒｒの変化により変動するので、
この値を補正するために、たとえば特開昭６０−３２２
８８号公報に見られるように、Ｒ１，Ｒ２の中点電圧Ｖ
T によりＶout ／ＶT を次の（３）式で求め、絶対湿度
出力とするものである。 但しＣは係数である。以上の（１）〜（３）式に示した
ように、第一の感温素子Ｒｓと第二の感温素子Ｒｒの比
を電圧変換して絶対湿度量を検出するものである。The output voltage V of the OP in such a configuration
out is represented by the following equation (2). However, Av is the above amplification factor, Av = Rf / Rc, Vf is the bridge circuit voltage, and Vf = Eo × Zs / (Zs
+ Rd) Zs is a combined resistance value of the bridge circuit, and Zs = (Rs + R
r) × (R1 + R2) / (Rs + Rr + R1 + R2). However, in the equation (2), since Vf changes due to changes in thermistor resistance values Rs and Rr due to temperature changes,
In order to correct this value, for example, JP-A-60-322.
As seen in Japanese Patent No. 88, the midpoint voltage V of R1 and R2
The absolute humidity output is obtained by calculating Vout / VT by the following equation (3) using T. However, C is a coefficient. As shown in the above equations (1) to (3), the ratio of the first temperature sensitive element Rs and the second temperature sensitive element Rr is converted into a voltage to detect the absolute humidity amount.
【０００８】[0008]
【発明が解決しようとする課題】図６、図７に雰囲気温
度がＴａ→Ｔｂ→Ｔｃと上昇しかつＴａ〜Ｔｂ間は絶対
湿度量が一定、Ｔｂ〜Ｔｃ間は徐々に湿度が増加する場
合の白金、サーミスタの場合のＲｒ−Ｒｓ特性を示す。
理想状態ではＴａ〜Ｔｂ間のＲｓ，Ｒｒの関係がＲｓ＝
Ｒｒであれば上記式でも明らかなように湿度変化があっ
ても絶対湿度量に変化がない限り出力は一定となる。し
かしながらこのような関係を持つＲｓ，Ｒｒの組み合わ
せの素子を選択するのは非常に困難であり現実にはＲｓ
＝Ａ×Ｒｒ＋Ｂ（Ａ，Ｂは係数）の１次式で現される関
係になっている。また極端な場合直線関係を維持出来て
いない場合もある。そのため絶対湿度量が変化せず温度
変化のみが生じたときにも出力が変化するいわゆる温度
ドリフトが発生していた。In FIGS. 6 and 7, the atmospheric temperature rises from Ta to Tb to Tc, the absolute humidity amount is constant between Ta and Tb, and the humidity gradually increases between Tb and Tc. 2 shows the Rr-Rs characteristics of the platinum and thermistor.
In an ideal state, the relationship between Rs and Rr between Ta and Tb is Rs =
With Rr, as is clear from the above equation, even if the humidity changes, the output is constant as long as the absolute humidity does not change. However, it is very difficult to select an element having a combination of Rs and Rr having such a relationship, and in reality, Rs
= A × Rr + B (A and B are coefficients). In extreme cases, the linear relationship may not be maintained. Therefore, a so-called temperature drift occurs in which the output changes even when the absolute humidity does not change and only the temperature changes.
【０００９】そこでこの対策として次の（イ），（ロ）
にのべるような対応策が従来とられていた。即ち （イ）特開昭６０−１４１４９号公報などに見られるよ
うに、Ｒｓ，Ｒｒのいずれかに補正用の抵抗を追加する
手段がある。これは上記のＲｓ＝Ａ×Ｒｒ＋Ｂの関係に
おいて、Ａを１とみなし、Ｂが正のときはＲｒに対しＢ
に相当する補正抵抗を、またＢが負のときはＲｓに対し
Ｂに相当する補正抵抗を、それぞれ直列に接続する。 （ロ）特開昭６０−２０３８１１号公報などに見られる
ように、温度変化によるＲｓ，Ｒｒの抵抗変化値により
素子に流れる電流値を制御し、例えば雰囲気温度が低下
すれば電流を増加させ素子の温度抵抗を抑え、雰囲気温
度が上昇すれば電流を減少させ素子の温度上昇を抑え、
それによって雰囲気温度変化によるＲｓ，Ｒｒの抵抗値
変化を小さくし、温度ドリフトを低減させる。Therefore, as measures against this, the following (a), (b)
The conventional measures have been taken. That is, (a) There is a means for adding a resistance for correction to either Rs or Rr as seen in JP-A-60-14149. In the above relationship of Rs = A × Rr + B, A is regarded as 1, and when B is positive, B is set to Rr.
A correction resistor corresponding to B is connected in series, and a correction resistor corresponding to B is connected in series with Rs when B is negative. (B) As seen in Japanese Patent Laid-Open No. 60-203811, etc., the value of the current flowing through the element is controlled by the resistance change values of Rs and Rr due to the temperature change. For example, if the atmospheric temperature decreases, the current is increased to increase the element. The temperature resistance of the device is suppressed, and if the ambient temperature rises, the current is reduced to suppress the temperature rise of the element,
As a result, changes in resistance values of Rs and Rr due to changes in ambient temperature are reduced, and temperature drift is reduced.
【００１０】しかしながら前記対応策（イ），（ロ）と
も次のような難点があり、いずれも充分とはいえない。
即ち （イ）の対応策では、Ａ＝１の場合のみに成立するもの
である上、現実に補正抵抗値を個別に設定することは困
難であるため、実際にはあらかじめ温度ドリフトの許容
範囲を設定し、その範囲内に収まるように補正抵抗値を
設定している。そのため、Ｒｓ，Ｒｒをある程度あらか
じめ選別しておく必要があった。 （ロ）の対応策では、補正効果は認められるものの、電
流制御量を設定する回路定数の決定に際して複数のパラ
メータが必要となり、また装置としては部品点数も多く
なるので、コスト、設計上などの困難が伴なった。 従って本発明の目的とするところは、簡易な手段により
温度ドリフトの発生を防止して雰囲気温度の条件にかか
わらず正確な湿度検出が可能となる湿度回路を提供する
ことにある。However, the above countermeasures (a) and (b) have the following drawbacks, and neither is sufficient.
That is, the countermeasure (a) is satisfied only when A = 1 and it is difficult to actually set the correction resistance values individually. Therefore, in practice, the allowable range of the temperature drift is set in advance. The correction resistance value is set so that it falls within the range. Therefore, it is necessary to select Rs and Rr in advance to some extent. In the countermeasure of (b), although the correction effect is recognized, a plurality of parameters are required for determining the circuit constant for setting the current control amount, and the number of parts of the device is large, so that the cost and the design are reduced. There were difficulties. Therefore, it is an object of the present invention to provide a humidity circuit capable of preventing temperature drift by a simple means and enabling accurate humidity detection regardless of ambient temperature conditions.
【００１１】[0011]
【課題を解決するための手段】本発明は以上の課題を解
決するためになされたものであって、その要旨とすると
ころは、密閉型と開放型の二つの感温素子より少なくと
も構成される第一の直列回路と二つの抵抗体より少なく
とも構成される第二の直列回路とをもってブリッジ回路
を構成するとともに前記感温素子を動作させる電源と前
記感温素子の抵抗比を電圧変換する電圧変換回路を具備
した湿度検出回路において、前記ブリッジ回路に流れる
電流値を制限するための第三の抵抗体を直列に接続しさ
らに第三の抵抗体の他方の端子に電流制御素子を接続
し、該電流制御素子と電源を接続し、第三の抵抗体の抵
抗値と動作時のブリッジ回路の合成抵抗との比に応じ
た、第四と第五の抵抗体を直列に接続し、該直列抵抗体
を電流制御素子と第三の抵抗体の接続点より第三の抵抗
体とブリッジ回路の直列接続体に対して並列に接続し、
第四と第五の抵抗体の接続点と、第三の抵抗体とブリッ
ジ回路の接続点をそれぞれ電圧比較回路に接続し、前記
電圧比較回路の出力を前記電流制御素子に入力させる構
成としたことを特徴とする湿度検出回路にある。SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the gist thereof is at least two thermosensitive elements, a closed type and an open type. A voltage conversion for forming a bridge circuit with a first series circuit and a second series circuit including at least two resistors, and for converting the resistance ratio of the power source and the temperature sensing element into a voltage. In a humidity detection circuit including a circuit, a third resistor for limiting a current value flowing in the bridge circuit is connected in series, and a current control element is further connected to the other terminal of the third resistor, The current control element and the power source are connected, and the fourth and fifth resistors are connected in series according to the ratio between the resistance value of the third resistor and the combined resistance of the bridge circuit during operation, and the series resistor is connected. Body with current control element and third Connected in parallel with the series connection of a third resistor and a bridge circuit from the connection point of the resistors,
The connection point of the fourth and fifth resistors and the connection point of the third resistor and the bridge circuit are respectively connected to the voltage comparison circuit, and the output of the voltage comparison circuit is input to the current control element. The humidity detecting circuit is characterized in that
【００１２】[0012]
【作用】第四、第五の抵抗体で設定された抵抗比を基準
として、雰囲気温度が変化し、第一、第二の感温素子の
抵抗値が変化しようとするとき電圧比較回路の出力によ
り感温素子に流れる電流値を制御し感温素子の動作温度
を一定に保ち、温度ドリフトの発生を防止する。When the ambient temperature changes and the resistance values of the first and second temperature sensitive elements try to change with reference to the resistance ratio set by the fourth and fifth resistors, the output of the voltage comparison circuit The current value flowing through the temperature-sensitive element is controlled by this to keep the operating temperature of the temperature-sensitive element constant and prevent temperature drift.
【００１３】[0013]
【実施例】以下図面に基いて本発明を説明する。本発明
の構成をブロック図的に示した回路図を図１に示す。同
図において、湿度検知器１は、先に従来技術の説明にお
いてのべた第一、第二の感温素子Ｒｓ，Ｒｒを直列に接
続したものであって、これらを第一、第二の抵抗体Ｒ
１，Ｒ２を直列に接続したものとによりブリッジ回路を
構成せしめるものである。さらに、第一、第二の感温素
子の接続点と第一、第二の抵抗体の接続点を電圧変換回
路２に接続する点は従来技術の説明においてのべた通り
である。ところで本発明においては、前記ブリッジ回路
に流れる電流値を制限するための第三の抵抗体Ｒ３また
はＲｄを該ブリッジ回路に直列に接続するとともに、抵
抗体Ｒ３の他方の端子に電流制御素子５を接続し、該素
子５と電流電圧Ｅｏの電源を接続し、抵抗体Ｒ３の抵抗
値と動作時のブリッジ回路の合成抵抗値との比に応じた
第四の抵抗体Ｒ４と第五の抵抗体Ｒ５が直列に接続され
ている。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. A circuit diagram showing a block diagram of the configuration of the present invention is shown in FIG. In the figure, the humidity detector 1 is one in which the first and second temperature sensitive elements Rs and Rr described in the description of the prior art are connected in series, and these are connected to the first and second resistances. Body R
A bridge circuit is formed by connecting 1 and R2 in series. Further, the connection points of the first and second temperature sensitive elements and the connection points of the first and second resistors are connected to the voltage conversion circuit 2 as described in the related art. By the way, in the present invention, the third resistor R3 or Rd for limiting the current value flowing in the bridge circuit is connected in series to the bridge circuit, and the current control element 5 is connected to the other terminal of the resistor R3. The fourth resistor R4 and the fifth resistor are connected according to the ratio of the resistance value of the resistor R3 to the combined resistance value of the bridge circuit in operation by connecting the element 5 and the power source of the current voltage Eo. R5 is connected in series.
【００１４】次にこの第四、第五の抵抗体Ｒ４，Ｒ５の
直列接続体を電流制御素子５と第三の抵抗体Ｒ３との接
続点より、第三の抵抗体Ｒ３とブリッジ回路との直列接
続体に対して並列に接続し、さらに第四の抵抗体Ｒ４と
第五の抵抗体Ｒ５の接続点と第三の抵抗体Ｒ３とブリッ
ジ回路の接続点をそれぞれ電圧比較回路４に接続し、該
電圧比較回路４の出力を電流制御素子５に入力するよう
構成されているものである。なお、前記のように感温素
子を含むブリッジ回路により絶対湿度量の検出を行なう
のは従来と同様であるが、第四及び第五の抵抗体Ｒ４，
Ｒ５の抵抗値は、動作時の感温素子の抵抗値から算出さ
れるブリッジ回路の合成抵抗値Ｚｓ（前述）及び電流制
限抵抗値Ｒｄ（或いは第三の抵抗値Ｒ３）で次のように
決まる。 Ｒ４／Ｒ５＝Ｒｄ／Ｚｓ 本発明の湿度検出回路は以上のような基本構成を有する
ものであるが、次に感温素子Ｒｓ，Ｒｒとして負の温度
特性を有する素子たとえばサーミスタを使用した場合の
実施例についてのべる。Next, the series connection body of the fourth and fifth resistors R4 and R5 is connected from the connection point of the current control element 5 and the third resistor R3 to the third resistor R3 and the bridge circuit. Connect in parallel to the series connection body, and further connect the connection point of the fourth resistor R4 and the fifth resistor R5 and the connection point of the third resistor R3 and the bridge circuit to the voltage comparison circuit 4, respectively. The output of the voltage comparison circuit 4 is input to the current control element 5. Although the absolute humidity is detected by the bridge circuit including the temperature sensitive element as described above, the fourth and fifth resistors R4 and R4 are used.
The resistance value of R5 is determined as follows by the combined resistance value Zs of the bridge circuit (described above) and the current limiting resistance value Rd (or the third resistance value R3) calculated from the resistance value of the temperature sensitive element during operation. .. R4 / R5 = Rd / Zs The humidity detecting circuit of the present invention has the basic configuration as described above. Next, when the temperature sensitive elements Rs and Rr are elements having negative temperature characteristics, for example, thermistors, are used. Reference will be made to Examples.
【００１５】図２は感温素子Ｒｓ，Ｒｒとしてサーミス
タを使用した場合の本発明の実施例を示すものであっ
て、ブリッジ回路及び演算処理部３を含む電圧変換回路
２については先にのべた図５の従来技術と同じである
が、この実施例においては、第四、第五の抵抗体Ｒ４，
Ｒ５の中点が抵抗Ｒ６を介して演算増幅器ＯＰ２の反転
入力端子に接続されており、一方、電流制限抵抗Ｒｄ即
ち第三の抵抗体Ｒ３とブリッジ回路との中点は抵抗Ｒ７
を介して演算増幅器ＯＰ２の非反転入力端子に接続され
ている。一方、第四の抵抗Ｒ４と電流制限抵抗Ｒｄの接
点はトランジスタＴｒのエミッタに接続されており、ま
た該トランジスタＴｒのトランジスタ、コレクタ間には
電流バイアス抵抗Ｒ８が並列に接続され、コレクタ端子
は負の電源電圧−Ｅｏの電源に接続されている。また演
算増幅器ＯＰ２の出力端子はトランジスタＴｒのベース
に接続されている。以上の構成で抵抗Ｒ６、Ｒ７及び演
算増幅器ＯＰ２により図１の電圧比較回路４が形成され
ており、またトランジスタＴｒ及び電流バイアス抵抗に
より図１の電流制御素子５が形成されている。FIG. 2 shows an embodiment of the present invention in which a thermistor is used as the temperature sensitive elements Rs and Rr, and the voltage conversion circuit 2 including the bridge circuit and the arithmetic processing section 3 is described above. This is the same as the prior art of FIG. 5, but in this embodiment, the fourth and fifth resistors R4,
The middle point of R5 is connected to the inverting input terminal of the operational amplifier OP2 via the resistor R6, while the middle point of the current limiting resistor Rd, that is, the third resistor R3 and the bridge circuit, is the resistor R7.
Is connected to the non-inverting input terminal of the operational amplifier OP2. On the other hand, the contact point between the fourth resistor R4 and the current limiting resistor Rd is connected to the emitter of the transistor Tr, the current bias resistor R8 is connected in parallel between the transistor and collector of the transistor Tr, and the collector terminal is negative. Connected to a power supply of -Eo. The output terminal of the operational amplifier OP2 is connected to the base of the transistor Tr. With the above configuration, the resistors R6 and R7 and the operational amplifier OP2 form the voltage comparison circuit 4 of FIG. 1, and the transistor Tr and the current bias resistor form the current control element 5 of FIG.
【００１６】次に図１，図２に示すように従来のブリッ
ジ回路に加えて第四、第五の抵抗体Ｒ４，Ｒ５ならびに
電圧比較回路４および電流制御素子５を設けた構成とさ
れた本発明の装置の動作について説明する。まず、あら
かじめ定めた雰囲気温度（サーミスタの動作抵抗Ｒｓ，
Ｒｒを定めた温度）より雰囲気温度が上昇すると、ブリ
ッジ回路の両端電圧は大きくなる（グランド側に近づ
く）。従って電圧比較回路４の演算増幅器ＯＰ２の出力
は小さくなり（負の側に大きくなる）電流制御回路５の
トランジスタＴｒのコレクターエミッタ間の電流が小さ
くなり従ってサーミスタＲｓ，Ｒｒの通電電流が減少し
自己加熱温度が下がり、第四、第五の抵抗体Ｒ４，Ｒ５
で定まった比率にたいして電流制限抵抗Ｒｄの値に応じ
たブリッジ部合成抵抗値Ｚｓで安定する。すなわち雰囲
気温度が上昇してもサーミスタＲｓ，Ｒｒの自己加熱温
度はあらかじめ定めた温度と変わらない。従って温度ド
リフトは発生しない。Next, as shown in FIGS. 1 and 2, in addition to the conventional bridge circuit, fourth and fifth resistors R4 and R5, a voltage comparison circuit 4 and a current control element 5 are provided. The operation of the device of the invention will be described. First, a predetermined ambient temperature (operating resistance Rs of the thermistor,
When the ambient temperature rises above Rr), the voltage across the bridge circuit increases (approaches the ground side). Therefore, the output of the operational amplifier OP2 of the voltage comparison circuit 4 becomes smaller (becomes larger on the negative side), the current between the collector and the emitter of the transistor Tr of the current control circuit 5 becomes smaller, and the conduction current of the thermistors Rs and Rr decreases, and the self-current decreases. The heating temperature drops, and the fourth and fifth resistors R4 and R5
The ratio is stabilized at the bridge combined resistance value Zs corresponding to the value of the current limiting resistance Rd. That is, even if the ambient temperature rises, the self-heating temperature of the thermistors Rs and Rr does not change from the predetermined temperature. Therefore, temperature drift does not occur.
【００１７】次に、本発明の装置を用いて湿度検出を行
なう手段についてのべる。湿度が変化した時の電流とサ
ーミスタの抵抗値Ｒｓ，ＲｒおよびＲｓ＋Ｒｒの特性を
図３に示す。図中Ｒｓ2 は湿度が増加したときの抵抗値
を示す。本発明の回路は雰囲気温度が変化してもＲｓ＋
Ｒｒの値を一定に保つことができる。そこで湿度が増加
しＲｓ＋Ｒｒの抵抗値がＲｓ2 ＋Ｒｒに変わった時は電
流が増加して（Ｒｓ＋Ｒｒ）＝（Ｒｓ2 ＋Ｒｒ）になる
ように電流値が変わりこの時の個々のサーミスタの値は
図中Ｒｓ0 ，Ｒｒ0 よりＲｓ1 ，Ｒｒ1 に変化してい
る。その結果Ｒｓ／Ｒｒの値が変化し従来どおり湿度検
出が可能となる。なお、ここで説明したのは負の温度特
性を有する感温素子であるサーミスタの場合であり、白
金等の正の温度特性を有する感温素子を用いる場合は演
算増幅器ＯＰ２の入力を入れ替えることで対応可能であ
ることは言うまでもない。Next, the means for detecting humidity using the apparatus of the present invention will be described. FIG. 3 shows the characteristics of the current and the resistance values Rs, Rr and Rs + Rr of the thermistor when the humidity changes. In the figure, Rs 2 represents the resistance value when the humidity increases. The circuit of the present invention has Rs + even if the ambient temperature changes.
The value of Rr can be kept constant. Therefore the value of the individual thermistor when a current is increased (Rs + Rr) = (Rs 2 + Rr) to become so current changes at this time the resistance value has changed to Rs 2 + Rr humidity increases Rs + Rr Figure It changes from Rs 0 and Rr 0 to Rs 1 and Rr 1 . As a result, the value of Rs / Rr changes and the humidity can be detected as in the conventional case. It should be noted that what has been described here is the case of a thermistor which is a temperature sensitive element having a negative temperature characteristic, and when a temperature sensitive element having a positive temperature characteristic such as platinum is used, the input of the operational amplifier OP2 can be replaced. Needless to say, it is possible.
【００１８】[0018]
【発明の効果】本発明によれば、簡易な手段により温度
ドリフトの発生を防止して雰囲気温度の条件にかかわら
ず正確な湿度検出が可能となるものであり、産業上の効
果は極めて顕著である。According to the present invention, the occurrence of temperature drift can be prevented by a simple means, and accurate humidity detection can be performed regardless of the ambient temperature conditions, and the industrial effect is extremely remarkable. is there.
【図１】本発明の構成をブロック図的に示す回路図であ
る。FIG. 1 is a circuit diagram showing a block diagram of a configuration of the present invention.
【図２】本発明の一実施例を示す回路図である。FIG. 2 is a circuit diagram showing an embodiment of the present invention.
【図３】サーミスタの抵抗値と通電電流の関係を示す特
性図である。FIG. 3 is a characteristic diagram showing a relationship between a resistance value of a thermistor and a conduction current.
【図４】白金抵抗体を用いた従来の湿度検出回路の一例
を示す回路図である。FIG. 4 is a circuit diagram showing an example of a conventional humidity detection circuit using a platinum resistor.
【図５】サーミスタを用いた従来の湿度検出回路の一例
を示す回路図である。FIG. 5 is a circuit diagram showing an example of a conventional humidity detection circuit using a thermistor.
【図６】白金抵抗体の場合のＲｒとＲｓの関係を示す特
性図である。FIG. 6 is a characteristic diagram showing a relationship between Rr and Rs in the case of a platinum resistor.
【図７】サーミスタの場合のＲｒとＲｓの関係を示す特
性図である。FIG. 7 is a characteristic diagram showing a relationship between Rr and Rs in the case of a thermistor.
１ 湿度検知器 ２ 電圧変換回路 ３ 演算処理部 ４ 電圧比較回路 ５ 電流制御素子 Ｒ１〜Ｒ８ 抵抗体 Ｒｓ，Ｒｒ 感温素子 Ｒｄ 電流制限抵抗体 ＯＰ，ＯＰ２ 演算増幅器 Ｒｃ ＯＰの入力抵抗 Ｒｆ ＯＰの負帰還抵抗 Ｖout ＯＰの出力電圧 Ｅｏ 電源電圧 Ｔｒ トランジスタ 1 Humidity Detector 2 Voltage Conversion Circuit 3 Arithmetic Processing Unit 4 Voltage Comparison Circuit 5 Current Control Elements R1 to R8 Resistors Rs, Rr Temperature Sensitive Elements Rd Current Limiting Resistors OP, OP2 Operational Amplifier Rc OP Input Resistance Rf OP Negative Feedback resistance Vout OP output voltage Eo Power supply voltage Tr transistor
Claims (3)
なくとも構成される第一の直列回路と二つの抵抗体より
少なくとも構成される第二の直列回路とをもってブリッ
ジ回路を構成するとともに前記感温素子を動作させる電
源と前記感温素子の抵抗比を電圧変換する電圧変換回路
を具備した湿度検出回路において、前記ブリッジ回路に
流れる電流値を制限するための第三の抵抗体を直列に接
続しさらに第三の抵抗体の他方の端子に電流制御素子を
接続し、該電流制御素子と電源を接続し、第三の抵抗体
の抵抗値と動作時のブリッジ回路の合成抵抗との比に応
じた、第四と第五の抵抗体を直列に接続し、該直列抵抗
体を電流制御素子と第三の抵抗体の接続点より第三の抵
抗体とブリッジ回路の直列接続体に対して並列に接続
し、第四と第五の抵抗体の接続点と、第三の抵抗体とブ
リッジ回路の接続点をそれぞれ電圧比較回路に接続し、
前記電圧比較回路の出力を前記電流制御素子に入力させ
る構成としたことを特徴とする湿度検出回路。1. A bridge circuit is constituted by a first series circuit including at least two temperature-sensing elements, a closed type and an open type, and a second series circuit including at least two resistors. In a humidity detection circuit including a power source for operating a temperature sensitive element and a voltage conversion circuit for converting a resistance ratio of the temperature sensitive element into a voltage, a third resistor for limiting a current value flowing in the bridge circuit is connected in series. The current control element is connected to the other terminal of the third resistor, the current control element is connected to the power source, and the ratio of the resistance value of the third resistor to the combined resistance of the bridge circuit during operation is set. According to, the fourth and fifth resistors are connected in series, and the series resistor is connected from the connection point of the current control element and the third resistor to the third resistor and the series connection body of the bridge circuit. Connected in parallel, the fourth and fifth resistors Connect the connection point of the body and the connection point of the third resistor and the bridge circuit to the voltage comparison circuit,
A humidity detecting circuit, wherein the output of the voltage comparing circuit is input to the current control element.
ある請求項１記載の湿度検出回路。2. The humidity detecting circuit according to claim 1, wherein the temperature sensitive element is an element having a positive temperature characteristic.
ある請求項１記載の湿度検出回路。3. The humidity detecting circuit according to claim 1, wherein the temperature sensitive element is an element having a negative temperature characteristic.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35171491A JP2673074B2 (en) | 1991-12-16 | 1991-12-16 | Humidity detection circuit |
| AU30015/92A AU657016B2 (en) | 1991-12-16 | 1992-12-08 | A circuit for humidity detection |
| KR1019920023949A KR960002807B1 (en) | 1991-12-16 | 1992-12-11 | A circuit for humidity detection |
| US07/990,241 US5345184A (en) | 1991-12-16 | 1992-12-14 | Humidity detection circuit for electronic heat cooking apparatus |
| EP92121334A EP0549947B1 (en) | 1991-12-16 | 1992-12-15 | A circuit for humidity detection |
| DE69223310T DE69223310T2 (en) | 1991-12-16 | 1992-12-15 | Moisture detection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35171491A JP2673074B2 (en) | 1991-12-16 | 1991-12-16 | Humidity detection circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05164721A true JPH05164721A (en) | 1993-06-29 |
| JP2673074B2 JP2673074B2 (en) | 1997-11-05 |
Family
ID=18419126
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35171491A Expired - Fee Related JP2673074B2 (en) | 1991-12-16 | 1991-12-16 | Humidity detection circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2673074B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006017681A (en) * | 2004-07-05 | 2006-01-19 | Noritz Corp | Humidity detector |
| CN102426178A (en) * | 2011-10-08 | 2012-04-25 | 黄宇嵩 | Bridge type humidity indicator for seedling raising shed |
| JP2016170161A (en) * | 2015-03-12 | 2016-09-23 | Tdk株式会社 | Thermal conductivity gas sensor |
| JP2017156293A (en) * | 2016-03-04 | 2017-09-07 | Tdk株式会社 | Gas detector |
| CN112378961A (en) * | 2020-11-24 | 2021-02-19 | 五邑大学 | Bionic flexible humidity sensor and electronic skin humidity monitoring device |
-
1991
- 1991-12-16 JP JP35171491A patent/JP2673074B2/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006017681A (en) * | 2004-07-05 | 2006-01-19 | Noritz Corp | Humidity detector |
| CN102426178A (en) * | 2011-10-08 | 2012-04-25 | 黄宇嵩 | Bridge type humidity indicator for seedling raising shed |
| JP2016170161A (en) * | 2015-03-12 | 2016-09-23 | Tdk株式会社 | Thermal conductivity gas sensor |
| JP2017156293A (en) * | 2016-03-04 | 2017-09-07 | Tdk株式会社 | Gas detector |
| CN112378961A (en) * | 2020-11-24 | 2021-02-19 | 五邑大学 | Bionic flexible humidity sensor and electronic skin humidity monitoring device |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2673074B2 (en) | 1997-11-05 |
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| LAPS | Cancellation because of no payment of annual fees |