JPH0353127A - Zero point correcting circuit - Google Patents
Zero point correcting circuitInfo
- Publication number
- JPH0353127A JPH0353127A JP1186087A JP18608789A JPH0353127A JP H0353127 A JPH0353127 A JP H0353127A JP 1186087 A JP1186087 A JP 1186087A JP 18608789 A JP18608789 A JP 18608789A JP H0353127 A JPH0353127 A JP H0353127A
- Authority
- JP
- Japan
- Prior art keywords
- voltage
- heater
- operational amplifier
- flow rate
- zero
- 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.)
- Granted
Links
- 239000003990 capacitor Substances 0.000 abstract description 6
- 238000012935 Averaging Methods 0.000 abstract 1
- 238000011144 upstream manufacturing Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000032683 aging Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Landscapes
- Measuring Volume Flow (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は流量測定装置に関し、特に、流量ゼロのときに
流量信号レベルがゼロになるように補正するゼロ点補正
回路に関するものである．〔従来の技術〕
第７図は、本発明回路が適用される流量測定センサチフ
プの一例を示す斜視図である。このようなチップ構造お
よび製法は、例えば特開昭６１−８８５３２号公報によ
り公知であって、その概要は、半導体チップ１０の上面
中央部につくりつけられたブリッジ１５の表面にヒータ
抵抗ＲＨと、これをはさんで温度センサＲＵ，ＲＤとが
設けられてなる。このようなセンサチップを流れの中に
置き、温度センサＲＵおよびＲＤが該流れの上・下流位
置となるような姿勢を与え（例えば矢印方向の流れの下
に置く）てヒータ抵抗ＲＨに通電すると、流れによって
、上流側センサＲＵは冷却され、下流側センサＲＤはヒ
ータ熱により加熱されるため、温度差を生じる。この温
度差を電圧値として取り出し流量出力とする。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flow rate measuring device, and in particular to a zero point correction circuit that corrects the flow rate signal level to zero when the flow rate is zero. [Prior Art] FIG. 7 is a perspective view showing an example of a flow rate measurement sensor chip to which the circuit of the present invention is applied. Such a chip structure and manufacturing method are known, for example, from Japanese Unexamined Patent Publication No. 61-88532, and the outline thereof is that a heater resistor RH is provided on the surface of a bridge 15 formed at the center of the upper surface of the semiconductor chip 10, and Temperature sensors RU and RD are provided between them. When such a sensor chip is placed in a flow, the temperature sensors RU and RD are placed in an upstream/downstream position of the flow (for example, placed under the flow in the direction of the arrow), and the heater resistor RH is energized. , the upstream sensor RU is cooled by the flow, and the downstream sensor RD is heated by the heater heat, resulting in a temperature difference. This temperature difference is taken out as a voltage value and is used as a flow rate output.
第４図は温度に対する上流側温度センサと下流側温度セ
ンサの出力レベルを示すグラフである．同図において、
Ａｌは下流側温度センサの特性を示す特性線、Ａ２は上
流側温度センサの特性を示す特性線である。第４図に示
すような特性を温度センサが持つ場合、（下流側温度セ
ンサの出力レベルー上流側温度センサの出力レベル）の
相対誤差を生じ、これは演算結果のゼロ点シフトとなっ
て現れる。下流側温度センサの出力特性ＳＤおよび上流
側温度センサの出力特性ＳＵを、ＳＤ＝ＡＤ − Ｔ＋
ＢＤ・・・・（１１ＳＵ＝ＡＵ−Ｔ＋ＢＵ・・・・（２
）
とすれば、相対誤差ΔＳは、（１１弐と（２）式から、
ΔＳ＝ （ＡＤ−ＡＵ）Ｔ＋ （ＢＤ−ＢＵ）・・・（
３）となる。相対誤差ΔＳの温度特性は第５図の特性線
Ｂ１のようになるが、ヒータオフ時のゼロ点補正により
第５図の特性線Ｂ２のように誤差を小さくすることがで
きる。しかし、ヒータオンにすると、第５図のＥ。８に
示すような誤差を生じるため、ゼロ点補正により誤差Ｅ
。Ｎをキャンセルする必要がある。Figure 4 is a graph showing the output levels of the upstream temperature sensor and downstream temperature sensor with respect to temperature. In the same figure,
Al is a characteristic line showing the characteristics of the downstream temperature sensor, and A2 is a characteristic line showing the characteristics of the upstream temperature sensor. When the temperature sensor has the characteristics shown in FIG. 4, a relative error of (output level of the downstream temperature sensor - output level of the upstream temperature sensor) occurs, and this appears as a zero point shift of the calculation result. The output characteristic SD of the downstream temperature sensor and the output characteristic SU of the upstream temperature sensor are defined as SD=AD − T+
BD・・・(11SU=AU-T+BU・・・・(2
), then the relative error ΔS is given by (112) and equation (2),
ΔS= (AD-AU)T+ (BD-BU)...(
3). Although the temperature characteristic of the relative error ΔS is as shown by the characteristic line B1 in FIG. 5, the error can be reduced as shown in the characteristic line B2 in FIG. 5 by zero point correction when the heater is turned off. However, when the heater is turned on, E in Figure 5. 8, the error E is reduced by zero point correction.
. It is necessary to cancel N.
誤差Ｅ。．４のキャンセルについて第６図（ａ）， （
ｂｌヲ用いて説明する。第６図において、１はヒータ回
路、ＲＨはヒータ抵抗、ＲＵは上流側温度センサとして
の抵抗、ＲＤは下流側温度センサとしての抵抗、Ｒ１と
Ｒ２は固定抵抗、ＶＲＩはバランス可変抵抗、ＶＲ２は
利得可変抵抗、ＶＲ３はオフセット調整可変抵抗、Ｕｌ
−Ｕ５は演算増幅器、３１〜Ｓ３はスイッチ、Ｃ１はコ
ンデンサである。Error E. ．． Regarding the cancellation of 4, Fig. 6(a), (
I will explain using blwo. In Figure 6, 1 is a heater circuit, RH is a heater resistance, RU is a resistance as an upstream temperature sensor, RD is a resistance as a downstream temperature sensor, R1 and R2 are fixed resistances, VRI is a balanced variable resistance, and VR2 is a resistance Gain variable resistor, VR3 is offset adjustment variable resistor, Ul
-U5 is an operational amplifier, 31 to S3 are switches, and C1 is a capacitor.
次に、第６図におけるゼロ点調整について述べる。まず
、バランス可変抵抗ＶＲＩにより、流量ゼロでヒータオ
フの時の上流側温度センサＲＵと下流側温度センサＲＤ
の出力電圧を一致させ、流量信号レベルＸをゼロとする
。Next, the zero point adjustment in FIG. 6 will be described. First, by using the balanced variable resistor VRI, the upstream temperature sensor RU and downstream temperature sensor RD when the flow rate is zero and the heater is off.
The output voltages of the two are matched, and the flow rate signal level X is set to zero.
演算増幅器Ｕ４．Ｕ５はゼロ点の経年変化を補正するも
ので、経年変化によるオフセント電圧■。，を取り込み
、 ＶＯＳを流量信号に加えることにより、オフセント
電圧ＶＯ３を解消するものである。Operational amplifier U4. U5 is to correct the secular change of the zero point, and the offset voltage due to the secular change ■. , and add VOS to the flow rate signal to eliminate the offset voltage VO3.
ＶＲ３はヒータオン時の第５図のＥ。Ｎに示すような誤
差ををキャンセルするための可変抵抗である。VR3 is E in Figure 5 when the heater is on. This is a variable resistor for canceling the error shown in N.
これはスイッチＳ１の節点ａに電圧ＶＡを与え、このＶ
Ａによりヒータオン時の誤差Ｅ。Ｎを打ち消すものであ
る。スイソチＳ１はヒータオフ時にａ接点側に倒れ、ヒ
ータオン時にｂ接点側に倒れる。This applies voltage VA to node a of switch S1, and this V
Error E when heater is turned on due to A. This cancels N. The switch S1 falls to the a contact side when the heater is off, and falls to the b contact side when the heater is on.
ヒータオフ時に、可変抵抗ＶＲ３で発生する電圧ＶＡを
ａ接点に印加することにより、ヒータオフとヒータオン
によって生じるオフセソトの差をキャンセルすることが
できる。可変抵抗ＶＲ３の調整はヒータオン、流量ゼロ
にして出荷時に行なう。By applying the voltage VA generated by the variable resistor VR3 to the a contact when the heater is off, it is possible to cancel the difference in offset caused by the heater being turned off and the heater being turned on. The variable resistor VR3 is adjusted at the time of shipment with the heater on and the flow rate zero.
このようにして、演算増幅器Ｕ５に電圧−ＶＯＳＶＡが
保持され、この電圧は、ヒータオンでスイッチＳ１がｂ
接点側に倒れたとき、演算増幅器Ｕ３に入力される。こ
れにより、経年変化によるオフセット■。Ｓとヒータオ
ンによる誤差Ｅ。Ｎとが打ち消される。In this way, a voltage -VOSVA is held in the operational amplifier U5, which voltage is the same as when the heater is on and the switch S1 is turned to b.
When it falls to the contact side, it is input to the operational amplifier U3. This results in offset due to aging ■. S and error E due to heater on. N is canceled out.
しかしながら、ヒータ抵抗ＲＨの経年変化によりヒータ
温度が変わったり、両方の温度センサにゴくが付着した
り、測定気体の種類が変わったりすることにより、温度
センサ付近の熱的条件が異なり、その結果ヒータオン時
の温度センサにおける温度Ｔ。Ｎが変化することがある
。ＴＯＮが一定でなくなると誤差Ｅ。２の値も変わるた
め、固定的なＥＯＮの補正だけでは十分でなく、結果的
にゼロ点がシフトしてしまうという欠点があった。However, as the heater temperature changes due to aging of the heater resistance RH, dirt adheres to both temperature sensors, and the type of gas being measured changes, the thermal conditions near the temperature sensor differ, resulting in Temperature T at the temperature sensor when the heater is on. N may change. Error E occurs when TON is no longer constant. Since the value of 2 also changes, fixed EON correction alone is not sufficient, and as a result, the zero point shifts.
本発明はこのような点に鑑みてなされたものであり、そ
の目的とするところは、ヒータ温度の変化、測定気体の
種類の違いによりゼロ点変動を生しないゼロ点補正回路
を得ることにある。The present invention has been made in view of these points, and its purpose is to provide a zero point correction circuit that does not cause zero point fluctuations due to changes in heater temperature or differences in the type of gas to be measured. .
このような目的を達成するために本発明は、流量ゼロに
おける流量信号のレベルがゼロになるように補正するゼ
ロ点補正回路において、ヒータオン時の平均測定電圧と
ヒータオフ時のオフ基準電圧との差電圧を発生する差電
圧発生回路を備え、上記差電圧によりヒータオン時の平
均測定電圧の変動を補正するようにしたものである。In order to achieve such an object, the present invention has a zero point correction circuit that corrects the level of the flow rate signal at zero flow rate to zero, and calculates the difference between the average measured voltage when the heater is on and the off reference voltage when the heater is off. The heater is equipped with a differential voltage generating circuit that generates a voltage, and uses the differential voltage to correct fluctuations in the average measured voltage when the heater is turned on.
本発明によるゼロ点補正回路においては、ヒータ温度の
変化、、測定気体の種類の違いによりゼロ点変動を生じ
ない。In the zero point correction circuit according to the present invention, zero point fluctuations do not occur due to changes in heater temperature or differences in the type of gas to be measured.
第１図（ａ）， （ｂｌは本発明によるゼロ点補正回路
の一実施例を示す回路図である。同図において、Ｕ６〜
ＵＩＯは演算増幅器、Ｓ４はスイッチ、ＶＲ４は可変抵
抗、Ｃ２はコンデンサであり、演算増幅器Ｕ７〜ＵＩＯ
は差電圧発生回路を構戒する。FIG. 1(a) and (bl) are circuit diagrams showing one embodiment of the zero point correction circuit according to the present invention.
UIO is an operational amplifier, S4 is a switch, VR4 is a variable resistor, C2 is a capacitor, and operational amplifiers U7 to UIO
Be wary of differential voltage generation circuits.
第１図において第６図と同一部分又は相当部分には同一
符号が付してある。In FIG. 1, the same or equivalent parts as in FIG. 6 are given the same reference numerals.
第６図の回路に対して付加されたのは、演算増幅器Ｕ６
〜ＵＩＯであり、演算増幅器Ｕ７およびＵ８により温度
センサＲＵとＲＤの両端電圧の加重平均値を演算して平
均測定電圧Ｖ。Ｎ（第２図参照）を出力する。温度セン
サＲＵとＲＤの出力電圧ＶＵとＶＤは流量に対して第２
図の曲線Ｃｌ，Ｃ２に示すように変化するが、ΔＶＤ＝
ＶＤ−Ｖ。、とΔＶＵ＝Ｖ．Ｎ−ＶＵの比は一定とみな
せるので、第１図の抵抗Ｒｌ．Ｒ２の値ｒｌ，ｒ２の比
を
ｒ １ ／ ｒ ２ ＝ΔＶＤ／ΔＶＵ ・ − ・
・（４）のように選べば、流量にかかわらず平均測定
電圧ＶＯＮの値を求めることができる。What is added to the circuit of FIG. 6 is an operational amplifier U6.
~ UIO, which calculates a weighted average value of the voltages across temperature sensors RU and RD using operational amplifiers U7 and U8 to obtain an average measured voltage V. N (see Figure 2) is output. The output voltages VU and VD of temperature sensors RU and RD are second to the flow rate.
It changes as shown in the curves Cl and C2 in the figure, but ΔVD=
VD-V. , and ΔVU=V. Since the ratio of N-VU can be regarded as constant, the resistance Rl. The ratio of R2 values rl and r2 is r 1 / r 2 = ΔVD/ΔVU ・ − ・
- By selecting as in (4), the value of the average measured voltage VON can be obtained regardless of the flow rate.
次に、第１図の回路におけるゼロ点調整法について述べ
る．まず、出荷時において、流量ゼロかつヒータオフと
し、バランス抵可変抵抗ＶＲＩを調整して、演算増幅器
Ｕ３から出力される流量信号レベルｖ０をゼロとする。Next, we will discuss the zero point adjustment method for the circuit shown in Figure 1. First, at the time of shipment, the flow rate is set to zero and the heater is turned off, and the balance variable resistor VRI is adjusted to set the flow rate signal level v0 output from the operational amplifier U3 to zero.
このとき温度センサＲＵ．ＲＤの出力電圧ＶＵ，ＶＤは
第２図の直線Ｃ３で示すように流量にかかわらず一致す
る。流量ゼロかつヒータオフのときはスイッチＳ４ぱオ
ンで、このときの演算増幅器Ｕ７の出力電圧Ｖ ＯＦＦ
はオフ基準電圧としてコンデンサＣ２に蓄積される。次
に、流量ゼロかつヒータオンとし、可変抵抗ＶＲ４を調
整して、出力電圧■。をゼロとする。At this time, the temperature sensor RU. The output voltages VU and VD of RD are the same regardless of the flow rate, as shown by straight line C3 in FIG. When the flow rate is zero and the heater is off, switch S4 is turned on, and the output voltage of operational amplifier U7 at this time is OFF.
is stored in capacitor C2 as an off reference voltage. Next, set the flow rate to zero and the heater to on, adjust the variable resistor VR4, and set the output voltage to ■. Let be zero.
流量ゼロかつヒータオンのときはスイッチＳ４はオフで
、このとき演算増幅器Ｕ９は、演算増幅器Ｕ７と演算増
幅器Ｕ８の出力電圧の差電圧を出力する。演算増幅器Ｕ
７は、温度センサＲＤ，ＲＵの出力電圧を固定抵抗Ｒｌ
，Ｒ２で加重平均した電圧Ｖ。、（平均測定電圧〉を出
力する。スイッチ８４オツにより演算増幅器Ｕ８は蓄積
されたオフ基準電圧■。ＦＦを出力する。出荷時等のよ
うな初期設定時の平均測定電圧Ｖ。．４を特にＶ。Ｎ０
と表わすと、初期設定時において流量ゼロかつヒータオ
ンのときの出力電圧ｖ０をゼロとするために可変抵抗Ｖ
Ｒ４から出力される補正電圧Ｅ。Ｈ０は、ＥｏＭｏ＝ｋ
（ＶＯＮ６ ＶＯＦＦ） ・・・１５１となる．
ｋは可変抵抗ＶＲ４の調整により定まるもので、演算増
幅器ＵＩＯの出力電圧の分圧比である。このように調整
することにより、第２図に示すように、温度センサＲＤ
とＲＵの出力電圧ＶＤとＶＵが流量ゼロで一致する。When the flow rate is zero and the heater is on, the switch S4 is off, and at this time the operational amplifier U9 outputs the difference voltage between the output voltages of the operational amplifier U7 and the operational amplifier U8. operational amplifier U
7 is a fixed resistor Rl that controls the output voltage of the temperature sensors RD and RU.
, R2 is the weighted average voltage V. , (average measured voltage) is output.The switch 84 causes the operational amplifier U8 to output the accumulated OFF reference voltage. V.N0
Expressed as
Correction voltage E output from R4. H0 is EoMo=k
(VON6 VOFF) ...151.
k is determined by adjusting the variable resistor VR4, and is a voltage division ratio of the output voltage of the operational amplifier UIO. By adjusting in this way, as shown in Fig. 2, the temperature sensor RD
and the output voltages VD and VU of RU match at zero flow rate.
しかし、流量ゼロかつヒータオンのときの一致した出力
電圧Ｖ。Ｍはヒータ温度の変化、測定気体の種類の違い
などにより変動し、出力電圧ＶＤとＶＵが一致しなくな
るので、この変動を補正する必要がある。補正は演算増
幅器Ｕ６に所定電圧を入力することにより行なう。この
所定電圧をＥ。Ｎとすると、（５）式と同様にして、
ＥＯＮ＝ ｋ （Ｖｏｓ Ｖｏｙｙ） ・・・・
（６）となる。この電圧を用いて、ヒータ温度の変化、
両方の温度センサへのゴごの付着、測定気体の種類の違
いなどによる流量信号レベルの変動を補正することがで
きる。However, the matched output voltage V when the flow rate is zero and the heater is on. Since M fluctuates due to changes in the heater temperature, differences in the type of gas to be measured, etc., and the output voltages VD and VU do not match, it is necessary to correct this fluctuation. Correction is performed by inputting a predetermined voltage to operational amplifier U6. This predetermined voltage is E. Assuming N, EON=k (Vos Voyy)... in the same way as equation (5).
(6) becomes. Using this voltage, change in heater temperature,
Fluctuations in the flow rate signal level due to dirt adhering to both temperature sensors, differences in the type of gas to be measured, etc. can be corrected.
次に、（６）式を実現する動作について述べる。ヒータ
オフ時に演算増幅器Ｕ７の出力電圧をスインチＳ４をオ
ンにしてコンデンサＣ２に蓄える。この電圧をＶ０，，
とする。演算増幅器Ｕ９は差動増幅器であるが、この場
合は正負の入力電圧が共にＶ ＯＦＦに等しいので、演
算増幅器Ｕ９の出力電圧はＯＶであり、反転増幅器とし
ての演算増幅器Ｕ１０は人力がＯｖなので、その出力電
圧もＯＶであり、演算増幅器Ｕ６の出力電圧もＯＶにな
る。Next, the operation to realize equation (6) will be described. When the heater is off, the output voltage of the operational amplifier U7 is stored in the capacitor C2 by turning on the switch S4. This voltage is V0,,
shall be. The operational amplifier U9 is a differential amplifier, but in this case, both the positive and negative input voltages are equal to V OFF, so the output voltage of the operational amplifier U9 is OV, and the operational amplifier U10 as an inverting amplifier has a human power of Ov. Its output voltage is also OV, and the output voltage of operational amplifier U6 is also OV.
次に、ヒータオン時に温度センサＲＵ．ＲＤの出力電圧
ＶＵ，ＶＤは上昇し、演算増幅器Ｕ７の出力電圧は平均
測定電圧ＶＯＮになる。ヒータオン時にスイッチＳ４を
オフにすると、演算増幅器Ｕ８は電圧Ｖ ＯＦＦを保っ
ているため、演算増幅器Ｕ９の出力電圧はＶ。Ｎ Ｖ
ＯＦＦ、演算増幅器ＵＩＯの出力電圧はＶ ＯＦＦ
Ｖ ＯＮとなり、可変抵抗ＶＲ４の両端にこれらの電圧
が印加され、可変抵抗ＶＲ４からは、（６）式に示す電
圧が出力される。Next, when the heater is turned on, the temperature sensor RU. The output voltages VU and VD of RD rise, and the output voltage of operational amplifier U7 becomes the average measured voltage VON. When the switch S4 is turned off when the heater is on, the output voltage of the operational amplifier U9 is V because the operational amplifier U8 maintains the voltage V OFF. NV
OFF, the output voltage of operational amplifier UIO is V OFF
V ON, these voltages are applied across the variable resistor VR4, and the voltage shown in equation (6) is output from the variable resistor VR4.
第１図（ａ）， （ｂ）はアナログ回路による演算を示
す回路図であるが、第３図（ａ）， （ｂ）に示すよう
に、Ａ／Ｄ変換器と演算装置を用いて、デジタル的にも
同等の演算が可能である。すなわち、温度センサＲＵ，
ＲＤ（７）両端電圧ＶＵ，ＶＤと電圧差（ＶＤ−ＶＵ）
を演算増幅器Ｕｌｌで増幅した電圧Ａ（Ｖ Ｄ − Ｖ
Ｕ） （ＡはＵｌｌの利得である）とをマルチブレ
クサ２で切り換えてＡ／Ｄ変換器３でＡ／Ｄ変換し、演
算装置４で処理する。流量ゼロのとき、演算結果（流量
信号レベル）Ｘがゼロになるように調整し、この調整値
をＦＲＯＭ５に書き込んでおき、以降の測定時に上記調
整値を使って補正を行なう。1(a) and 1(b) are circuit diagrams showing calculations using analog circuits, but as shown in FIGS. 3(a) and 3(b), using an A/D converter and a calculation device, Equivalent calculations are also possible digitally. That is, temperature sensor RU,
RD (7) Both ends voltage VU, VD and voltage difference (VD - VU)
The voltage A (V D − V
U) (A is the gain of Ull) is switched by the multiplexer 2, A/D converted by the A/D converter 3, and processed by the arithmetic unit 4. When the flow rate is zero, the calculation result (flow rate signal level) is adjusted so that it becomes zero, this adjustment value is written in FROM 5, and the adjustment value is used to perform correction during subsequent measurements.
以上説明したように本発明は、ヒータオン時の平均測定
電圧とヒータオフ時のオフ基準電圧との差電圧を発生す
る差電圧発生回路を設け、上記差電圧によりヒータオン
時の平均測定電圧の変動を補正するようにしたことによ
り、ヒータオン時の平均測定電圧が変化しても流量ゼロ
のときの流量信号レベルをゼロに維持できるので、ヒー
タ温度の変化、両方の温度センサへのゴξの付着、測定
気体の種類の違いがあっても、ゼロ点が変動しないとい
う効果がある。As explained above, the present invention provides a differential voltage generation circuit that generates a differential voltage between the average measured voltage when the heater is on and the off reference voltage when the heater is off, and uses the differential voltage to correct fluctuations in the average measured voltage when the heater is on. By doing so, the flow rate signal level at zero flow rate can be maintained at zero even if the average measured voltage when the heater is on changes, so it is possible to maintain the flow rate signal level at zero when the flow rate is zero. This has the effect that the zero point does not change even if there are differences in the type of gas.
【図面の簡単な説明】
第１図は本発明によるゼロ点補正回路の一実施例を示す
回路図、第２図は温度センサ出力電圧対流量の特性を示
すグラフ、第３図は本発明の第２の実施例を示す回路図
、第４図は温度センサ出力電圧対温度の特性を示すグラ
フ、第５図は温度センサ相対誤差対温度の特性を示すグ
ラフ、第６図は従来のゼロ点補正回路を示す回路図、第
７図は本発明回路が適用される流量測定センサチップの
一例を示す斜視図である．
１・・・ヒータ回路、ＲＵ・・・上流側温度センサ、Ｒ
Ｄ・・・下流側温度センサ、Ｒｌ，Ｒ２・・・固定抵抗
、ＲＨ・・・ヒータ抵抗、Ｕｌ−’ＵＩＯ・・・演算増
幅器、ＶＲＩ・・・バランス可変抵抗、ＶＲ２・・・利
得可変抵抗、ＶＲ４・・・可変抵抗、８１〜Ｓ４・・・
スイッチ、ＣＩ．Ｃ２・・・コンデンサ。[Brief Description of the Drawings] Fig. 1 is a circuit diagram showing an embodiment of the zero point correction circuit according to the present invention, Fig. 2 is a graph showing the characteristics of temperature sensor output voltage versus flow rate, and Fig. 3 is a circuit diagram showing an embodiment of the zero point correction circuit according to the present invention. A circuit diagram showing the second embodiment, FIG. 4 is a graph showing the temperature sensor output voltage versus temperature characteristic, FIG. 5 is a graph showing the temperature sensor relative error versus temperature characteristic, and FIG. 6 is the conventional zero point. A circuit diagram showing a correction circuit, and FIG. 7 is a perspective view showing an example of a flow rate measurement sensor chip to which the circuit of the present invention is applied. 1... Heater circuit, RU... Upstream temperature sensor, R
D...downstream temperature sensor, Rl, R2...fixed resistance, RH...heater resistance, Ul-'UIO...operational amplifier, VRI...balance variable resistor, VR2...variable gain resistor , VR4...variable resistor, 81~S4...
Switch, CI. C2... Capacitor.
Claims (1)
補正するゼロ点補正回路において、ヒータオン時の平均
測定電圧とヒータオフ時のオフ基準電圧との差電圧を発
生する差電圧発生回路を備え、前記差電圧により前記ヒ
ータオン時の平均測定電圧の変動を補正するゼロ点補正
回路。A zero point correction circuit that corrects the level of a flow rate signal at zero flow rate to zero, includes a difference voltage generation circuit that generates a difference voltage between an average measured voltage when the heater is on and an off reference voltage when the heater is off, and A zero point correction circuit that corrects fluctuations in the average measured voltage when the heater is turned on based on the voltage.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1186087A JPH0663802B2 (en) | 1989-07-20 | 1989-07-20 | Zero correction circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1186087A JPH0663802B2 (en) | 1989-07-20 | 1989-07-20 | Zero correction circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0353127A true JPH0353127A (en) | 1991-03-07 |
| JPH0663802B2 JPH0663802B2 (en) | 1994-08-22 |
Family
ID=16182144
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1186087A Expired - Lifetime JPH0663802B2 (en) | 1989-07-20 | 1989-07-20 | Zero correction circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0663802B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5311762A (en) * | 1991-12-16 | 1994-05-17 | Dxl Usa | Flow sensor calibration |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0187209U (en) * | 1987-12-01 | 1989-06-08 |
-
1989
- 1989-07-20 JP JP1186087A patent/JPH0663802B2/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0187209U (en) * | 1987-12-01 | 1989-06-08 |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5311762A (en) * | 1991-12-16 | 1994-05-17 | Dxl Usa | Flow sensor calibration |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0663802B2 (en) | 1994-08-22 |
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