JPH02147915A - Hot wire type air flowmeter - Google Patents

Hot wire type air flowmeter

Info

Publication number
JPH02147915A
JPH02147915A JP63300580A JP30058088A JPH02147915A JP H02147915 A JPH02147915 A JP H02147915A JP 63300580 A JP63300580 A JP 63300580A JP 30058088 A JP30058088 A JP 30058088A JP H02147915 A JPH02147915 A JP H02147915A
Authority
JP
Japan
Prior art keywords
voltage
output
hot wire
constant temperature
pass filter
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
Application number
JP63300580A
Other languages
Japanese (ja)
Other versions
JP2690980B2 (en
Inventor
Hiroshi Yoneda
浩志 米田
Masayoshi Suzuki
鈴木 政善
Masuo Akamatsu
赤松 培雄
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Hitachi Automotive Systems Engineering Co Ltd
Original Assignee
Hitachi Automotive Engineering Co Ltd
Hitachi Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Hitachi Automotive Engineering Co Ltd, Hitachi Ltd filed Critical Hitachi Automotive Engineering Co Ltd
Priority to JP63300580A priority Critical patent/JP2690980B2/en
Publication of JPH02147915A publication Critical patent/JPH02147915A/en
Application granted granted Critical
Publication of JP2690980B2 publication Critical patent/JP2690980B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Abstract

PURPOSE:To avoid effect on a voltage control oscillator by providing a low-pass filter between a constant temperature control circuit and an output voltage adjusting circuit within a voltage output type hot wire type air flowmeter. CONSTITUTION:Current IH flowing through a hot wire 105 is detected with a resistance 106 to serve output signal V2 of a constant temperature control circuit 1. Here, when an air flow vibrates by a turbulence or the like, the V2 fluctuates as well and so, the fluctuation of the V2 is suppressed with a low-pass filter 2 down to a VF. The VF is amplified with a differential amplifier 304 of an output adjusting circuit 3 to match characteristic of a voltage control oscillator 4 at the rear stage. This enables suppression of a variation in a frequency output due to vibration of an air flow without affecting the constant temperature control circuit 1 and the voltage control oscillator 4.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は周波数出力形熱線式空気流量計における出力周
波数の変動防止に関する。
DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to prevention of fluctuations in output frequency in a frequency output type hot wire air flowmeter.

〔従来の技術〕[Conventional technology]

従来の周波数出力形熱線式空気流量計は、ACスパーク
社マス・エアフローセンサ取扱説明書に記載のように、
電圧出力形熱線式空気流量計の後段に電圧制御発振器が
接続されている。また、従来の電圧制御発振器は1日立
産業用リニア・アイ・シーデータブック(昭和61年7
月)第86頁に記載のように、入力段にローパスフィル
タが形成されている。つまり、従来の周波数出力形熱線
式空気流量計は第3図のように定温度制御回路lと出力
電圧調整回路3を有する電圧出力形熱線式空気流量計5
の出力電圧の振動を、ローパスフィルタ2で減衰し電圧
制御発振r14により周波数出力に変換する構成となっ
ている。
The conventional frequency output type hot wire air flow meter is as described in the AC Spark mass air flow sensor instruction manual.
A voltage controlled oscillator is connected after the voltage output type hot wire air flow meter. In addition, the conventional voltage controlled oscillator is
As described on page 86, a low-pass filter is formed at the input stage. In other words, the conventional frequency output type hot wire air flow meter has a voltage output type hot wire air flow meter 5 which has a constant temperature control circuit 1 and an output voltage adjustment circuit 3 as shown in FIG.
The vibration of the output voltage is attenuated by the low-pass filter 2 and converted into a frequency output by the voltage controlled oscillation r14.

〔発明が解決しようとする課題〕[Problem to be solved by the invention]

上記従来技術は電圧制御発振器の入力インピーダンスが
低いため、入力段に形成されているローパスフィルタ内
の抵抗値を小さくし、電圧制御発振器への影響を回避す
る必要があった。それにともない、コンデンサの容量が
大きくなり、集積化が困難であった。
In the above conventional technology, since the input impedance of the voltage controlled oscillator is low, it is necessary to reduce the resistance value in the low-pass filter formed in the input stage to avoid the influence on the voltage controlled oscillator. As a result, the capacitance of the capacitor has increased, making integration difficult.

本発明の目的は、電圧制御発振器及び電圧出力形熱線式
空気流量計に影響を与えず、集積化可能な周波数出力形
熱線式空気流量計を構成することにある。
An object of the present invention is to construct a frequency output type hot wire type air flow meter that can be integrated without affecting the voltage controlled oscillator and the voltage output type hot wire type air flow meter.

〔課題を解決するための手段〕[Means to solve the problem]

上記目的を達成するために、第3図のように電圧出力形
熱線式空気流量計5と電圧制御発振器4の間に設けられ
ていたローパスフィルタ2を、第2図のように電圧出力
形熱線式空傑JE量計内の定温度制御回路1と出力電圧
調整回路3の間にローパスフィルタ2を設けるものであ
る。
In order to achieve the above object, the low-pass filter 2 installed between the voltage output type hot wire air flow meter 5 and the voltage controlled oscillator 4 as shown in FIG. A low-pass filter 2 is provided between a constant temperature control circuit 1 and an output voltage adjustment circuit 3 in the JE quantity meter.

〔作用〕[Effect]

電圧出力形熱線式空気流量計内の出力電圧調整回路は、
差動増幅器で構成されることが多いので高入力インピー
ダンス、低出力インピーダンスとなっている。このため
、ローパスフィルタを定温度制御回路と出力電圧調整回
路の間に挿入し、出力電圧調整回路と電圧制御発振器を
直接つなぐと。
The output voltage adjustment circuit in the voltage output type hot wire air flow meter is
Since it is often constructed from a differential amplifier, it has high input impedance and low output impedance. For this reason, insert a low-pass filter between the constant temperature control circuit and the output voltage adjustment circuit, and connect the output voltage adjustment circuit and the voltage controlled oscillator directly.

ローパスフィルタが電圧制御発振器に影響を及ぼすこと
はほとんどなく、小刻みな電圧変動が周波数出力に現わ
れることはない、定温度制御回路は低出力インピーダン
スのため、ローパスフィルタの影響を受けない。そのた
め、ローパスフィルタのコンデンサ容量を小さくシ、抵
抗値を大きくすれば、集積化が可能となる。
The low-pass filter has little effect on the voltage-controlled oscillator, and small voltage fluctuations do not appear in the frequency output.The constant temperature control circuit has a low output impedance, so it is not affected by the low-pass filter. Therefore, if the capacitor capacity of the low-pass filter is made small and the resistance value is made large, integration becomes possible.

〔実施例〕〔Example〕

以下、本発明の一実施例を第1−図により説明する。 EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the present invention will be described with reference to FIG.

第1図において、熱線105を流れる電流Inはにin
gの式より(1)式で示される。
In FIG. 1, the current In flowing through the hot wire 105 is in
From the equation of g, it is shown by equation (1).

一方、差動増幅器107.抵抗器106,104゜10
3、空気温度を検出する補償抵抗102.トランジスタ
101により(1)式の(To−Ta) /I2Hは常
に一定値に制御される。従って(1)式より電流IHは
(2)式となり、この電流II+は抵抗106で検出さ
れ、定温度制御回路の出力信号V2となる。
On the other hand, the differential amplifier 107. Resistor 106, 104°10
3. Compensation resistor 102 for detecting air temperature. (To-Ta)/I2H in equation (1) is always controlled to a constant value by the transistor 101. Therefore, from equation (1), current IH becomes equation (2), and this current II+ is detected by resistor 106 and becomes the output signal V2 of the constant temperature control circuit.

I H= ((A 十B Jσ) / C) z−(2
)ここで空気流が乱流等により振動すれば、■2も振動
するため、ローパスフィルタ2により、■2の振動を抑
えVFとする。ローパスフィルタの遮断周波数Fcは(
3)式である。
I H= ((A 1 B Jσ) / C) z-(2
) Here, if the airflow vibrates due to turbulence or the like, (2) also vibrates, so the low-pass filter 2 suppresses the vibration (2) and makes it VF. The cutoff frequency Fc of the low-pass filter is (
3) is the formula.

Fc = (2x RC) −’       −(3
)〔R;抵抗201の抵抗値、C;コンデンサ202の
静電容量〕 このVFを出力調整回路3の差動増幅器304で、後段
の電圧制御発振器4の特性に合わせる様に増幅する。V
FI VO,FOの伝達関数は(4)。
Fc = (2x RC) −' −(3
) [R: resistance value of resistor 201, C: capacitance of capacitor 202] This VF is amplified by the differential amplifier 304 of the output adjustment circuit 3 so as to match the characteristics of the voltage controlled oscillator 4 at the subsequent stage. V
The transfer functions of FI VO and FO are (4).

(5)式で示される。It is shown by equation (5).

4XCvXR405XΔVT 第4図は、第1図のローパスフィルタ2の他の実施例で
あり、コンデンサ42の容量をトランジスタ43で等価
的に増幅している。この回路の遮断周波数Fcは(5)
式となる。
4XCvXR405XΔVT FIG. 4 shows another embodiment of the low-pass filter 2 shown in FIG. 1, in which the capacitance of the capacitor 42 is equivalently amplified by a transistor 43. The cutoff frequency Fc of this circuit is (5)
The formula becomes

・・・(4) の静電容量 第4図の実施例によるとローパスフィルタ2のコンデン
サ42の静電容量は更に小さくするととができる。
(4) Capacitance According to the embodiment shown in FIG. 4, the capacitance of the capacitor 42 of the low-pass filter 2 can be further reduced.

第5図は、ローパスフィルタ2の他の実施例であり、コ
ンデンサ52の容量を電界効果トランジスタ53で等価
的に増幅して、上記と同様にコンデンサ52の容量を小
さくすることができる。
FIG. 5 shows another embodiment of the low-pass filter 2, in which the capacitance of the capacitor 52 can be equivalently amplified by a field effect transistor 53 to reduce the capacitance of the capacitor 52 in the same manner as described above.

第6図は、ローパスフィルタ2の他の実施例であり、ダ
イオード62の逆バイアス時の接合容量を利用したもの
である。この実施例によれば、PN接合のみでローパス
フィルタを形成できるため、集積化が更に容易になる。
FIG. 6 shows another embodiment of the low-pass filter 2, which utilizes the junction capacitance of the diode 62 when reverse biased. According to this embodiment, the low-pass filter can be formed using only a PN junction, which further facilitates integration.

〔発明の効果〕〔Effect of the invention〕

本発明によれば、定温度制御回路及び電圧制御発振器に
影響を与えずに空気流の振動による周波数出力の変動を
抑制できるので周波数出力形熱線式空気流量計の精度を
向上する効果がある。
According to the present invention, fluctuations in frequency output due to air flow vibration can be suppressed without affecting the constant temperature control circuit and the voltage controlled oscillator, thereby improving the accuracy of the frequency output type hot wire air flowmeter.

また、ローパスフィルタのコンデンサ容量を小さくでき
るので、集積化が可能となる。
Furthermore, since the capacitance of the low-pass filter capacitor can be reduced, integration becomes possible.

【図面の簡単な説明】[Brief explanation of the drawing]

第1図は本発明の一実施例を示す図、第2図は本発明の
基本構成図、第3図は従来の周波数出力形熱線式空気流
量計の基本構成図、第4図、第5図及び第6図はローパ
スフィルタの他の実施例を示す図である。 1・・・定温度制御回路、2・・ローパスフィルタ、3
・・・出力電圧調整回路、4・・・電圧制御発振器。 第1図 第2因 第3図
Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a basic configuration diagram of the present invention, Fig. 3 is a basic configuration diagram of a conventional frequency output type hot wire air flow meter, Figs. FIG. 6 and FIG. 6 are diagrams showing other embodiments of the low-pass filter. 1... Constant temperature control circuit, 2... Low pass filter, 3
... Output voltage adjustment circuit, 4... Voltage controlled oscillator. Figure 1 Cause 2 Figure 3

Claims (1)

【特許請求の範囲】[Claims] 1、熱線を定温度に保持するために電流を供給し、かつ
該電流を電圧信号として出力する定温度制御回路、前記
電圧信号を増幅する出力電圧調整回路、該出力を周波数
信号に変換する電圧制御発振器から成る周波数出力形熱
線式空気流量計において、検出電圧の振動を抑制するロ
ーパスフィルタを、定温度制御回路と出力電圧調整回路
の間に設けたことを特徴とする熱線式空気流量計。
1. A constant temperature control circuit that supplies current to maintain the hot wire at a constant temperature and outputs the current as a voltage signal, an output voltage adjustment circuit that amplifies the voltage signal, and a voltage that converts the output into a frequency signal. A frequency output type hot wire air flow meter comprising a controlled oscillator, characterized in that a low pass filter for suppressing vibration of the detection voltage is provided between a constant temperature control circuit and an output voltage adjustment circuit.
JP63300580A 1988-11-30 1988-11-30 Thermal air flow meter Expired - Lifetime JP2690980B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP63300580A JP2690980B2 (en) 1988-11-30 1988-11-30 Thermal air flow meter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP63300580A JP2690980B2 (en) 1988-11-30 1988-11-30 Thermal air flow meter

Publications (2)

Publication Number Publication Date
JPH02147915A true JPH02147915A (en) 1990-06-06
JP2690980B2 JP2690980B2 (en) 1997-12-17

Family

ID=17886550

Family Applications (1)

Application Number Title Priority Date Filing Date
JP63300580A Expired - Lifetime JP2690980B2 (en) 1988-11-30 1988-11-30 Thermal air flow meter

Country Status (1)

Country Link
JP (1) JP2690980B2 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1703262A1 (en) * 2005-03-14 2006-09-20 Texas Instruments Incorporated System and method for regulating bridge voltage in a intermittently heated hot-wire anemometer
JP2011190676A (en) * 2010-03-10 2011-09-29 National Oilwell Varco Lp Drilling hole device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1703262A1 (en) * 2005-03-14 2006-09-20 Texas Instruments Incorporated System and method for regulating bridge voltage in a intermittently heated hot-wire anemometer
JP2011190676A (en) * 2010-03-10 2011-09-29 National Oilwell Varco Lp Drilling hole device

Also Published As

Publication number Publication date
JP2690980B2 (en) 1997-12-17

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