JPH0486524A - Liquid level detector - Google Patents
Liquid level detectorInfo
- Publication number
- JPH0486524A JPH0486524A JP20185090A JP20185090A JPH0486524A JP H0486524 A JPH0486524 A JP H0486524A JP 20185090 A JP20185090 A JP 20185090A JP 20185090 A JP20185090 A JP 20185090A JP H0486524 A JPH0486524 A JP H0486524A
- Authority
- JP
- Japan
- Prior art keywords
- resistance element
- heat
- temperature
- reference potential
- detection 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.)
- Pending
Links
- 239000007788 liquid Substances 0.000 title claims abstract description 63
- 238000001514 detection method Methods 0.000 claims abstract description 68
- 239000000758 substrate Substances 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 4
- 230000004304 visual acuity Effects 0.000 abstract 1
- 230000007423 decrease Effects 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
Landscapes
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
Description
本発明は発熱性感温抵抗素子を用いた液面レベル検出器
に関する。本発明は、例えば、自動車の燃料レベル測定
器に応用できる。The present invention relates to a liquid level detector using a heat-generating temperature-sensitive resistance element. The present invention can be applied, for example, to a fuel level measuring device for an automobile.
従来、この種の検出器として、段階的に検出される液面
レベルに対応した位置において、複数個のサーミスタを
配列したものが知られている。
この検出器は、サーミスタへの通電により発生した熱の
放熱効率が、サーミスタが測定液中にある場合と気中に
ある場合とで大きく異なることを利用している。サーミ
スタの発熱による温度上昇は、それが液中にある方が気
中にある方よりも小さい。従って、サーミスタが始め液
中に存在し、液面レベルの低下に伴い気中に露出される
と、サーミスタの温度が急峻に上昇する。サーミスタが
負性抵抗係数を有する場合には、温度上昇によりその抵
抗値が著しく低下する。どのサーミスタの抵抗値が急激
に変化したかによって、気中に露出状態になったサーミ
スタが分かり、それにより液面レベルが検出される。Conventionally, as this type of detector, one in which a plurality of thermistors are arranged at positions corresponding to the liquid level that is detected in stages is known. This detector utilizes the fact that the efficiency of dissipating heat generated by energizing the thermistor differs greatly between when the thermistor is in the liquid to be measured and when it is in the air. The temperature rise due to heat generated by a thermistor is smaller when it is in liquid than when it is in air. Therefore, when the thermistor initially exists in the liquid and is exposed to the air as the liquid level decreases, the temperature of the thermistor rises sharply. When a thermistor has a negative resistance coefficient, its resistance value decreases significantly as the temperature increases. Depending on which thermistor's resistance value has suddenly changed, it can be determined which thermistor is exposed to the air, and the liquid level can then be detected.
上記の検出器で、測定される液面レベルの分解能を向上
させるためには、サーミスタの配設間隔を狭くする必要
がある。しかし、サーミスタの配設間隔を狭くすると、
サーミスタの放熱が隣接するサーミスタに伝わり、液中
にあるサーミスタの抵抗値が低下するため、液面レベル
の誤検出が行われるという問題がある。
一方、サーミスタの発熱量を低くすれば、発熱による影
響も少なく、サーミスタの配設間隔を狭くとれることに
なる。
しかし、例えば、自動車の燃料の場合には、液体の温度
は、−１０℃から６０℃の広範囲に存在することになる
。このように温度が広範囲に渡る液体の液面レベルを測
定するには、サーミスタの温度上昇をその温度範囲より
充分に大きくとる必要がある。従って、測定対象の液体
の温度範囲が広い場合には、サーミスタの発熱量を低下
させることができないのでサーミスタの配設間隔を狭く
することができず、液面レベル測定の分解能を向上させ
ることが困難であった。
本発明は上記課題を解決するために成されたものであり
、その目的は、液面レベル測定の分解能を向上させるこ
とである。In order to improve the resolution of the liquid level measured by the above detector, it is necessary to narrow the spacing between the thermistors. However, if the thermistor spacing is narrowed,
There is a problem in that the heat dissipated from the thermistor is transmitted to the adjacent thermistor, and the resistance value of the thermistor submerged in the liquid decreases, resulting in erroneous detection of the liquid level. On the other hand, if the amount of heat generated by the thermistor is reduced, the effect of heat generation will be reduced, and the spacing between the thermistors can be narrowed. However, for example, in the case of automobile fuel, the temperature of the liquid will exist over a wide range of -10°C to 60°C. In order to measure the liquid level of a liquid whose temperature ranges over a wide range as described above, it is necessary that the temperature rise of the thermistor be sufficiently larger than the temperature range. Therefore, if the temperature range of the liquid to be measured is wide, it is not possible to reduce the amount of heat generated by the thermistor, so the spacing between the thermistors cannot be narrowed, and the resolution of liquid level measurement cannot be improved. It was difficult. The present invention has been made to solve the above problems, and its purpose is to improve the resolution of liquid level measurement.
上記課題を解決するための発明の構成は、抵抗素子と発
熱性感温抵抗素子との直列接続から成るレベル検出回路
と、レベル検出回路が液面レベルが変化する方向に多数
配置された基板と、基板に配設され、抵抗素子とレベル
検出回路の発熱性感温抵抗素子の温度抵抗特性とほぼ同
一の特性を有する発熱性感温抵抗素子との直列接続によ
る基準電位発生回路と、基準電位発生回路の接続点から
基準電位を、それぞれのレベル検出回路の接続点から検
出電位を入力するそれぞれの比較器とを有し、非発熱状
態において、基準電位発生回路の抵抗素子と発熱性感温
抵抗素子との抵抗比をレベル検出回路の抵抗素子と発熱
性感温抵抗素子との抵抗比と略整合のとれた状態で、基
準電位発生回路の抵抗素子と発熱性感温抵抗素子との抵
抗値の和を、レベル検出回路の抵抗素子と発熱性感温抵
抗素子との抵抗値の和に比べて、充分に大きくしたこと
である。The configuration of the invention for solving the above problems includes: a level detection circuit including a resistance element and a heat-generating temperature-sensitive resistance element connected in series; a substrate in which a large number of level detection circuits are arranged in the direction in which the liquid level changes; A reference potential generation circuit that is arranged on a substrate and is connected in series with a resistance element and a heat-generating temperature-sensitive resistance element that has almost the same temperature resistance characteristics as the heat-generating temperature-sensitive resistance element of the level detection circuit; Each comparator inputs a reference potential from a connection point and a detection potential from a connection point of each level detection circuit, and in a non-heating state, the resistance element of the reference potential generation circuit and the heat-generating temperature-sensitive resistance element are connected. When the resistance ratio is approximately matched with the resistance ratio of the resistance element of the level detection circuit and the heat-generating temperature-sensitive resistance element, the sum of the resistance values of the resistance element of the reference potential generation circuit and the heat-generating temperature-sensitive resistance element is determined as the level. The resistance value is made sufficiently larger than the sum of the resistance values of the resistance element of the detection circuit and the heat-generating temperature-sensitive resistance element.
本検出器ではレベル検出回路と基準電位発生回路とで全
ブリッジ回路が形成される。そのブリッジ回路の２つの
出力が、それぞれのレベル検出回路に対応する比較器に
入力する。２つの出力は、レベル検出回路の抵抗素子と
発熱性感温抵抗素子との接続点の電位（検出電位）と、
基準電位発生回路における抵抗素子と発熱性感温抵抗素
子との接続点の電位（基準電位）である。
基準電位発生回路の発熱性感温抵抗素子の温度抵抗特性
は、レベル検出回路の発熱性感温抵抗素子のそれとほぼ
等しくなるように設定されている。
このことは、両回路の発熱性感温抵抗素子を同一素子と
することで容易に実現できる。
又、基準電位発生回路の抵抗素子と非発熱状態の発熱性
感温抵抗素子との抵抗比は、レベル検出回路の対応する
抵抗比と略整合がとれた値に設定されている。従って、
液面レベルの測定される液体の温度が広範囲に変化して
も、検出電位と基準電位は共に同様な温度特性で変化す
るので、両者の電位差はあまり変化しない。
しかし、基準電位発生回路の抵抗比をレベル検出回路の
抵抗比と完全に等しくすると、比較器の出力が不安定と
なるので、レベル検出回路の通電による発熱による発熱
性感温抵抗素子の抵抗変化量を考慮して、安定動作が可
能な範囲で両者の抵抗比に差が設けられている。
尚、そのレベル検出回路の発熱性感温抵抗素子が液中に
存在する状態から気中に露出した状態に変化する時、検
出電位が基準電位を越えて変化するように、レベル検出
回路と基準電位発生回路との抵抗比が設定されている。
この結果、液中から気中に露出した状態に変化するレベ
ル検出回路に対応する比較器の出力レベルが、液面レベ
ルの変化に伴って反転する。
一方、基準電位発生回路の抵抗素子と非発熱状態にある
発熱性感温抵抗素子の総合抵抗は、その抵抗比がレベル
検出回路の抵抗比と略整合した状態で、大きな値に設定
されている。従って、基準電位発生回路を流れる電流値
は小さく、その発熱性感温抵抗素子の発熱量は少ない。
従って、基準電位発生回路の発熱性感温抵抗素子が気中
に露出された状態となっても、基準電位の変動は少ない
。
従って、このような状態となっても、各比較器の出力が
反転することはなく、正確な液面レベルが検出される。In this detector, a full bridge circuit is formed by the level detection circuit and the reference potential generation circuit. The two outputs of the bridge circuit are input to a comparator corresponding to each level detection circuit. The two outputs are the potential at the connection point between the resistance element of the level detection circuit and the heat-generating temperature-sensitive resistance element (detection potential), and
This is the potential (reference potential) at the connection point between the resistance element and the heat-generating temperature-sensitive resistance element in the reference potential generation circuit. The temperature resistance characteristic of the heat generating temperature sensitive resistance element of the reference potential generation circuit is set to be approximately equal to that of the heat generating temperature sensitive resistance element of the level detection circuit. This can be easily realized by using the same heat-generating temperature-sensitive resistance element in both circuits. Further, the resistance ratio between the resistance element of the reference potential generation circuit and the heat-generating temperature-sensitive resistance element in a non-heat generating state is set to a value that substantially matches the corresponding resistance ratio of the level detection circuit. Therefore,
Even if the temperature of the liquid whose liquid level is to be measured changes over a wide range, the detection potential and the reference potential both change with similar temperature characteristics, so the potential difference between them does not change much. However, if the resistance ratio of the reference potential generation circuit is made completely equal to the resistance ratio of the level detection circuit, the output of the comparator will become unstable. In consideration of this, a difference is provided in the resistance ratio between the two within a range that allows stable operation. The level detection circuit and the reference potential are set so that when the heat-generating temperature-sensitive resistance element of the level detection circuit changes from being in the liquid to being exposed to the air, the detection potential changes beyond the reference potential. The resistance ratio with the generating circuit is set. As a result, the output level of the comparator corresponding to the level detection circuit that changes from being in the liquid to being exposed to the air is reversed as the liquid level changes. On the other hand, the total resistance of the resistance element of the reference potential generation circuit and the heat-generating temperature-sensitive resistance element in the non-heat generating state is set to a large value with the resistance ratio substantially matching the resistance ratio of the level detection circuit. Therefore, the value of the current flowing through the reference potential generation circuit is small, and the amount of heat generated by the heat-generating temperature-sensitive resistance element is small. Therefore, even if the heat-generating temperature-sensitive resistance element of the reference potential generation circuit is exposed to the air, the reference potential does not fluctuate much. Therefore, even in such a state, the output of each comparator will not be reversed, and an accurate liquid level will be detected.
以下、本発明を具体的な一実施例に基づいて説明する。
第１図において、長尺状の絶縁基板１の上に多数のレベ
ル検出回路１０がその長さ方向に沿って配設されている
。絶縁基板１の長さ方向は測定される液面レベルの変化
する方向である。
絶縁基板１は熱容量を小さくするために、ポリイミド等
の薄いフレキシブルプリント基板で構成されている。
レベル検出回路１０は、それぞれ、絶縁基板１上に形成
された電極２１．２２によって並列接続されている。レ
ベル検出回路１０は抵抗素子３と発熱性感温抵抗素子２
とで構成されている。発熱性感温抵抗素子２は負性温度
抵抗係数を有するサーミスタで構成されている。この発
熱性感温抵抗素子２に通電することで発熱し、温度上昇
に伴ってその抵抗値が低下する。この発熱性感温抵抗素
子２はその他、白金抵抗体等の温度に依存して抵抗の変
化する抵抗体で構成することもできる。
一方、絶縁基板１の最低位置に基準電位発生回路１１が
形成されている。その基準電位発生回路１１は、レベル
検出回路１０と同様に抵抗素子５と複数（本実施例では
３個）の発熱性感温抵抗素子４の直列接続回路である。
この発熱性感温抵抗素子４はレベル検出回路１００発熱
性感温抵抗素子２と同一の素子が用いられている。従っ
て、発熱性感温抵抗素子２と発熱性感温抵抗素子４とは
温度抵抗特性が等しい。
この基準電位発生回路１１は液体の温度が変化しても、
正確な液面レベルが検出されるように温度補償を行うた
めの回路である。
液面レベルを検出するために、各レベル検出回路１０に
対応して、各比較器３０が設けられている。
第２図に示すように、各比較器３０の非反転入力端子に
は、対応するレベル検出回路１０における抵抗素子３と
発熱性感温抵抗素子２との接続点の電位が入力し、各比
較器３００反転入力端子には、基準電位発生回路１１に
おける抵抗素子５と発熱性感温抵抗素子４との接続点の
電位が入力している。
電極２１と電極２２との間で、直流電圧が印加されてお
り、各レベル検出回路１０と基準電位発生回路１１とは
、全ブリッジ回路を構成している。従って、各比較器３
０は各全ブリッジ回路の平衡出力を入力している。
次に本検出回路の作動について説明する。
（１）検出電位と基準電位との関係
レベル検出回路１０において、非発熱状態で、抵抗素子
３の抵抗値に対する発熱性感温抵抗素子２の抵抗値の比
（抵抗比）をｒとする。本実施例では抵抗比ｒは１であ
る。又、基準電位発生回路１１の同様に定義される抵抗
比をＲとする。本実施例では抵抗比Ｒは約０．８に設定
されている。
一般に、発熱性感温抵抗素子２が液中にある状態から気
中に露出した状態に変化する時に、レベル検出回路１０
の出力である検出電位が低下するような使用の場合には
、両者の抵抗比の関係は、ｒ〉Ｒの関係に設定される。
従って、発熱性感温抵抗素子２が液中に存在するレベル
検出回路１０の検出電位ｖ１は基準電位Ｓ１よりも高く
設定されている。
従って、液面レベルが最高位置にある時には、各比較器
３０の出力は高レベルである。
尚、測定対象の液体のとり得る全温度範囲及び外乱温度
変動によるレベル検出回路１０と基準電位発生回路１１
との温度差に対して、常に、検出電位ｖ１が基準電位Ｓ
ｌよりも高くなるように設定されている。即ち、検出電
位ｖ１が基準電位Ｓ１よりも高くなるように、上記の抵
抗比ｒと抵抗比Ｒが設定されている。
（２）液面レベルの検出
電極２１と電極２２の間に電位が印加されると、各レベ
ル検出回路１００発熱性感温抵抗素子２及び基準電位発
生回路１１の発熱性感温抵抗素子４に電流が流れ、発熱
性感温抵抗素子２及び発熱性感温抵抗素子４は発熱する
。液中に存在する発熱性感温抵抗素子２は液体で効率良
く冷却されるので、その温度上昇はない。一方、液面レ
ベルが低下して気中に露出された発熱性感温抵抗素子２
は気体での冷却効果が少なく、熱平衡に達する温度まで
上昇する。この結果、気中にあるレベル検出回路１０の
検出電位ｖ２は基準電位Ｓ１より低くなる。この時、基
準電位発生回路１１は液中に存在するので、発熱性感温
抵抗素子４の温度上昇はなく、基準電位ｓｌは変化しな
い。
従って、各比較器３０の出力により、ランプ等を駆動す
れば、液面レベルの低下に伴って、ランプが順次消灯す
ることになる。このランプ等の消灯又は点灯状態によっ
て、現在の液面レベルを知ることができる。
（３）温度補償
液面レベルの測定の対象となる液体の温度は、広範囲で
変動する。この温度変動に伴って、発熱性感温抵抗素子
２．４の液中に存在する時の抵抗値が変化し、検出電位
と基準電位が液体の温度変動に伴って変化する。
しかし、レベル検出回路１０における発熱性感温抵抗素
子２と基準電位発生回路１１における発熱性感温抵抗素
子４の温度抵抗特性は等しくなるように設定されている
。即ち、同じ規格の製品素子が用いられている。又、レ
ベル検出回路１０の抵抗比ｒと基準電位発生回路１１の
抵抗比Ｒも、上述したように、はぼ整合している。従っ
て、液体の温度変動があっても、液中に存在するレベル
検出回路１０の検出電位ｖ１と基準電位Ｓ１は、温度に
対してほぼ同じ特性で変化することになり、各比較器３
０の入力電位の差は液体の温度に対してほとんど変化し
ない。従って、各比較器３０の出力の液体の温度に対す
る安定性が確保される。
このような液体温度による補償が行われているので、発
熱性感温抵抗素子２の発熱量は、それが気中に露出され
た状態で、液体温度に対して約３０℃位上昇する発熱量
で充分測定可能である。従って、発熱量を低く抑えられ
るので、発熱性感温抵抗素子２の配列間隔を狭くするこ
とが可能となり、液面レベルの測定分解能を向上させる
ことができる。
（４）空状態の補償
液面レベルが検出可能範囲を越えて低下すると、基準電
位検出回路１１０発熱性感温抵抗素子４が気中に露出す
ることになる。
しかし、基準電位検出回路１１の抵抗素子４の抵抗値と
発熱性感温抵抗素子４の抵抗値との和の総合抵抗値は、
レベル検出回路１０の総合抵抗値よりも充分に高く設定
されている。本実施例では、発熱性感温抵抗素子４は同
じ素子を３個用いており、抵抗素子５の抵抗値が抵抗素
子３の抵抗値の５倍の値となっており、抵抗比ｋを０．
８としている。
従って、基準電位発生回路１１の発熱性感温抵抗素子４
の発熱量はレベル検出回路１０の発熱性感温抵抗素子２
の発熱量に比べて充分に少ない。従って、この時の基準
電位Ｓ２は発熱性感温抵抗素子４が液中に存在する時の
基準電位Ｓｌに対して、余り、変化しない。
従って、基準電位が変化しないので、比較器３゜の出力
も安定する。
尚、もしも、基準電位発生回路１１の発熱性感温抵抗素
子４を１個だけ用いて、その発熱量をレベル検出回路１
０の発熱性感温抵抗素子２の発熱量と同じとすると、基
準電位発生回路１１が気中に露出した時に、発熱性感温
抵抗素子４の抵抗値が大きく減少する。この結果、基準
電位も大きく低下し、レベル検出回路１０の露出時の検
出電位ｖ２よりも低下することになる。すると、各比較
器３０の出力は一斉に高レベルとなり、ランプ等が液体
のフル状態と同じく、全て点灯することになる。
本実施例では、液体の空状態におけるこのような誤表示
を防止することができる。The present invention will be described below based on a specific example. In FIG. 1, a large number of level detection circuits 10 are arranged on a long insulating substrate 1 along its length. The length direction of the insulating substrate 1 is the direction in which the measured liquid level changes. The insulating substrate 1 is made of a thin flexible printed circuit board made of polyimide or the like in order to reduce heat capacity. The level detection circuits 10 are connected in parallel by electrodes 21 and 22 formed on the insulating substrate 1, respectively. The level detection circuit 10 includes a resistance element 3 and a heat-generating temperature-sensitive resistance element 2.
It is made up of. The heat-generating temperature-sensitive resistance element 2 is composed of a thermistor having a negative temperature resistance coefficient. When the heat-generating temperature-sensitive resistance element 2 is energized, it generates heat, and its resistance value decreases as the temperature rises. The heat-generating temperature-sensitive resistance element 2 can also be composed of a resistor whose resistance changes depending on the temperature, such as a platinum resistor. On the other hand, a reference potential generation circuit 11 is formed at the lowest position of the insulating substrate 1. The reference potential generation circuit 11, like the level detection circuit 10, is a series connection circuit of a resistance element 5 and a plurality (three in this embodiment) of heat-generating temperature-sensitive resistance elements 4. The heat-generating temperature-sensitive resistance element 4 is the same as the heat-generating temperature-sensitive resistance element 2 of the level detection circuit 100. Therefore, the heat-generating temperature-sensitive resistance element 2 and the heat-generating temperature-sensitive resistance element 4 have the same temperature resistance characteristics. Even if the temperature of the liquid changes, this reference potential generation circuit 11
This circuit performs temperature compensation so that accurate liquid level is detected. In order to detect the liquid level, each comparator 30 is provided corresponding to each level detection circuit 10. As shown in FIG. 2, the potential at the connection point between the resistance element 3 and the heat-generating temperature-sensitive resistance element 2 in the corresponding level detection circuit 10 is input to the non-inverting input terminal of each comparator 30. The potential at the connection point between the resistance element 5 and the heat-generating temperature-sensitive resistance element 4 in the reference potential generation circuit 11 is input to the 300 inversion input terminal. A DC voltage is applied between the electrodes 21 and 22, and each level detection circuit 10 and reference potential generation circuit 11 constitute a full bridge circuit. Therefore, each comparator 3
0 inputs the balanced output of each full bridge circuit. Next, the operation of this detection circuit will be explained. (1) Relationship between detection potential and reference potential In the level detection circuit 10, in a non-heating state, the ratio (resistance ratio) of the resistance value of the heat-generating temperature-sensitive resistance element 2 to the resistance value of the resistance element 3 is defined as r. In this embodiment, the resistance ratio r is 1. Further, let R be the similarly defined resistance ratio of the reference potential generation circuit 11. In this embodiment, the resistance ratio R is set to approximately 0.8. Generally, when the exothermic temperature-sensitive resistance element 2 changes from a state in a liquid to a state exposed in the air, the level detection circuit 10
In the case of use in which the detection potential which is the output of is reduced, the relationship between the resistance ratios of both is set to be r>R. Therefore, the detection potential v1 of the level detection circuit 10 in which the heat-generating temperature-sensitive resistance element 2 is present in the liquid is set higher than the reference potential S1. Therefore, when the liquid level is at the highest level, the output of each comparator 30 is at a high level. In addition, a level detection circuit 10 and a reference potential generation circuit 11 based on the entire temperature range that the liquid to be measured can take and disturbance temperature fluctuations.
The detected potential v1 is always equal to the reference potential S for the temperature difference between
It is set to be higher than l. That is, the resistance ratio r and the resistance ratio R are set so that the detected potential v1 is higher than the reference potential S1. (2) When a potential is applied between the liquid level detection electrode 21 and the electrode 22, a current flows through the heat generating temperature sensitive resistance element 2 of each level detection circuit 100 and the heat generating temperature sensitive resistance element 4 of the reference potential generation circuit 11. As a result, the heat-generating temperature-sensitive resistance element 2 and the heat-generating temperature-sensitive resistance element 4 generate heat. Since the exothermic temperature-sensitive resistance element 2 existing in the liquid is efficiently cooled by the liquid, its temperature does not rise. On the other hand, the exothermic temperature-sensitive resistance element 2 is exposed to the air due to a drop in the liquid level.
The cooling effect of gas is small, and the temperature rises to reach thermal equilibrium. As a result, the detection potential v2 of the level detection circuit 10 in the air becomes lower than the reference potential S1. At this time, since the reference potential generation circuit 11 is present in the liquid, the temperature of the heat-generating temperature-sensitive resistance element 4 does not rise, and the reference potential sl does not change. Therefore, if lamps and the like are driven by the output of each comparator 30, the lamps will be turned off one after another as the liquid level decreases. The current liquid level can be known by the off or on state of this lamp, etc. (3) Temperature compensation The temperature of the liquid that is the subject of liquid level measurement varies over a wide range. With this temperature fluctuation, the resistance value of the exothermic temperature-sensitive resistance element 2.4 when it exists in the liquid changes, and the detection potential and the reference potential change with the temperature fluctuation of the liquid. However, the temperature resistance characteristics of the heat generating temperature sensitive resistance element 2 in the level detection circuit 10 and the heat generating temperature sensitive resistance element 4 in the reference potential generation circuit 11 are set to be equal. That is, product elements of the same standard are used. Further, as described above, the resistance ratio r of the level detection circuit 10 and the resistance ratio R of the reference potential generation circuit 11 are also closely matched. Therefore, even if there is a temperature change in the liquid, the detection potential v1 of the level detection circuit 10 and the reference potential S1 existing in the liquid will change with almost the same characteristics with respect to the temperature, and each comparator 3
The zero input potential difference changes little with respect to the temperature of the liquid. Therefore, the stability of the output of each comparator 30 with respect to the temperature of the liquid is ensured. Since such compensation is performed based on the liquid temperature, the amount of heat generated by the heat-generating temperature-sensitive resistance element 2 is approximately 30 degrees Celsius higher than the liquid temperature when it is exposed to the air. It is fully measurable. Therefore, since the amount of heat generated can be suppressed to a low level, it is possible to narrow the arrangement interval of the heat-generating temperature-sensitive resistance elements 2, and it is possible to improve the measurement resolution of the liquid level. (4) Compensation in empty state If the liquid level falls beyond the detectable range, the reference potential detection circuit 110 and the heat-generating temperature-sensitive resistance element 4 will be exposed to the air. However, the total resistance value of the sum of the resistance value of the resistance element 4 of the reference potential detection circuit 11 and the resistance value of the heat-generating temperature-sensitive resistance element 4 is
It is set sufficiently higher than the total resistance value of the level detection circuit 10. In this embodiment, three of the same heat-generating temperature-sensitive resistance elements 4 are used, the resistance value of the resistance element 5 is five times the resistance value of the resistance element 3, and the resistance ratio k is set to 0.
It is set at 8. Therefore, the heat-generating temperature-sensitive resistance element 4 of the reference potential generation circuit 11
The amount of heat generated by the heat-generating temperature-sensitive resistance element 2 of the level detection circuit 10 is
The calorific value is significantly lower than that of Therefore, the reference potential S2 at this time does not change much from the reference potential Sl when the heat-generating temperature-sensitive resistance element 4 is present in the liquid. Therefore, since the reference potential does not change, the output of the comparator 3° is also stable. If only one heat-generating temperature-sensitive resistance element 4 of the reference potential generation circuit 11 is used, the amount of heat generated by the heat-generating temperature-sensitive resistance element 4 of the reference potential generation circuit 11 is measured by the level detection circuit 1.
Assuming that the amount of heat generated is the same as that of the heat-generating temperature-sensitive resistance element 2 at zero, the resistance value of the heat-generating temperature-sensitive resistance element 4 decreases significantly when the reference potential generation circuit 11 is exposed to the air. As a result, the reference potential also decreases significantly, and becomes lower than the detection potential v2 of the level detection circuit 10 when exposed. Then, the output of each comparator 30 becomes high level all at once, and the lamps and the like are all turned on, just like when the liquid is in a full state. In this embodiment, such erroneous display when the liquid is empty can be prevented.
本発明では、抵抗素子と発熱性感温抵抗素子との直列接
続から成るレベル検出回路と、抵抗素子とレベル検出回
路の発熱性感温抵抗素子の温度抵抗特性とほぼ同一の特
性を有する発熱性感温抵抗素子との直列接続による基準
電位発生回路との全ブリッジ回路の出力で液面レベルを
検出するようにしている。従って、環境温度による影響
が排除できるので、レベル検出回路の発熱性感温抵抗素
子の発熱量を低くできる。この結果、発熱性感温抵抗素
子の配列間隔を狭くすることができ、液面レベルの測定
分解能を向上させることができる。
又、本発明は、非発熱状態において、基準電位発生回路
における抵抗比をレベル検出回路における抵抗比と略整
合のとれた状態として、基準電位発生回路の総合抵抗値
をレベル検出回路の総合抵抗値に比べて、充分に大きく
しているので、基準電位発生回路が気中に露出しても、
発熱性感温抵抗素子の発熱量が少なく、従って、基準電
位を安定化できるので、液体の空状態における液面レベ
ルの測定信号が安定する。The present invention includes a level detection circuit consisting of a series connection of a resistance element and a heat-generating temperature-sensitive resistance element, and a heat-generating temperature-sensitive resistor having almost the same temperature resistance characteristics as the temperature resistance characteristic of the heat-generating temperature-sensitive resistance element of the resistance element and the level detection circuit. The liquid level is detected by the output of a full bridge circuit with a reference potential generation circuit connected in series with the element. Therefore, since the influence of environmental temperature can be eliminated, the amount of heat generated by the heat-generating temperature-sensitive resistance element of the level detection circuit can be reduced. As a result, the arrangement interval of the heat-generating temperature-sensitive resistance elements can be narrowed, and the measurement resolution of the liquid level can be improved. Further, in the present invention, the total resistance value of the reference potential generation circuit is set to the total resistance value of the level detection circuit in a state where the resistance ratio in the reference potential generation circuit is substantially matched with the resistance ratio in the level detection circuit in a non-heating state. Since it is sufficiently large compared to , even if the reference potential generation circuit is exposed to the air,
Since the amount of heat generated by the heat-generating temperature-sensitive resistance element is small, and therefore the reference potential can be stabilized, the measurement signal of the liquid level when the liquid is empty is stabilized.
第１図は本発明の具体的な一実施例に係る液面レベル検
出器の構成を示した平面図、第２図は同実施例に係る液
面レベル検出器の電気的構成を示した回路図である。
１ 絶縁基板 ２，４°発熱性感温抵抗素子３．５°抵
抗素子 １０ レベル検出回路１１−基準電位発生回
路２１．２２°゛電極３０°゛比較器FIG. 1 is a plan view showing the configuration of a liquid level detector according to a specific embodiment of the present invention, and FIG. 2 is a circuit diagram showing the electrical configuration of the liquid level detector according to the same embodiment. It is a diagram. 1 Insulating substrate 2.4° exothermic temperature sensitive resistance element 3.5° resistance element 10 Level detection circuit 11-reference potential generation circuit 21.22° electrode 30° comparator
Claims (1)
により発熱する発熱性感温抵抗素子との直列接続から成
るレベル検出回路と、 前記レベル検出回路が測定対象の液面レベルが変化する
方向に多数配置された基板と、 前記基板に配設され、抵抗素子と前記レベル検出回路の
前記発熱性感温抵抗素子の温度抵抗特性とほぼ同一の特
性を有する発熱性感温抵抗素子との直列接続による基準
電圧発生回路と、 前記基準電圧発生回路の抵抗素子と発熱性感温抵抗素子
との接続点の電位を基準電位とし、前記それぞれのレベ
ル検出回路の抵抗素子と発熱性感温抵抗素子との接続点
の電位を検出電位とし、前記基準電位と前記検出電位を
入力するそれぞれの比較器と を有し、 非発熱状態において、前記基準電位発生回路の抵抗素子
と発熱性感温抵抗素子との抵抗比を前記レベル検出回路
の抵抗素子と発熱性感温抵抗素子との抵抗比と略整合の
とれた状態で、前記基準電位発生回路の抵抗素子と発熱
性感温抵抗素子との抵抗値の和を、前記レベル検出回路
の抵抗素子と発熱性感温抵抗素子との抵抗値の和に比べ
て、充分に大きくした液面レベル検出器。[Scope of Claims] A level detection circuit consisting of a series connection of a resistance element and a heat-generating temperature-sensitive resistance element whose resistance value changes depending on temperature and which generates heat when energized; a plurality of substrates arranged in a direction in which the level changes; and a heat-generating temperature-sensitive resistance element disposed on the substrate and having almost the same temperature resistance characteristics as the resistance element and the heat-generating temperature-sensitive resistance element of the level detection circuit. a reference voltage generation circuit connected in series with the reference voltage generation circuit, and a potential at a connection point between the resistance element of the reference voltage generation circuit and the heat-generating temperature-sensitive resistance element as a reference potential; A potential at a connection point with the element is set as a detection potential, and each comparator inputs the reference potential and the detection potential, and in a non-heating state, the resistance element of the reference potential generation circuit and the heat-generating temperature-sensitive resistance element The resistance value of the resistance element of the reference potential generation circuit and the heat-generating temperature-sensitive resistance element is determined in a state where the resistance ratio of the resistance element of the level detection circuit and the heat-generating temperature-sensitive resistance element is substantially matched. A liquid level detector in which the sum is sufficiently larger than the sum of the resistance values of the resistance element and the heat-generating temperature-sensitive resistance element of the level detection circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20185090A JPH0486524A (en) | 1990-07-30 | 1990-07-30 | Liquid level detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20185090A JPH0486524A (en) | 1990-07-30 | 1990-07-30 | Liquid level detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0486524A true JPH0486524A (en) | 1992-03-19 |
Family
ID=16447924
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20185090A Pending JPH0486524A (en) | 1990-07-30 | 1990-07-30 | Liquid level detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0486524A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002067716A (en) * | 2000-08-31 | 2002-03-08 | Fuji Heavy Ind Ltd | Canister arrangement structure for automobile |
| DE102009035857A1 (en) | 2008-08-08 | 2010-03-25 | Suzuki Motor Corp., Hamamatsu-Shi | Collector mounting structure |
| JP2016133310A (en) * | 2015-01-15 | 2016-07-25 | 新明和工業株式会社 | Tank-equipped wheeled vehicle |
-
1990
- 1990-07-30 JP JP20185090A patent/JPH0486524A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002067716A (en) * | 2000-08-31 | 2002-03-08 | Fuji Heavy Ind Ltd | Canister arrangement structure for automobile |
| DE102009035857A1 (en) | 2008-08-08 | 2010-03-25 | Suzuki Motor Corp., Hamamatsu-Shi | Collector mounting structure |
| US8177259B2 (en) | 2008-08-08 | 2012-05-15 | Suzuki Motor Corporation | Canister mounting structure |
| JP2016133310A (en) * | 2015-01-15 | 2016-07-25 | 新明和工業株式会社 | Tank-equipped wheeled vehicle |
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