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Air Flow Meter (Hot Wire) Waveform Notes
The voltage output from the Air Flow Meter (AFM) should be linear to airflow and this can be measured on an oscilloscope and should look similar to the example shown.
The waveform should show approximately 1.0 Volt when the engine is at idle, this voltage will rise as the engine is accelerated and air volume is increased producing an initial peak. This peak is due to the initial influx of air and drops momentarily before the voltage is seen to rise again to another peak of approximately 4.0 to 4.5 Volts. This voltage will however depend on how hard the engine is accelerated, a lower voltage is not necessarily a fault within the AFM.
On deceleration the voltage will drop sharply as the throttle butterfly closes, reducing the airflow, and the engine returns back to idle. The final voltage will drop gradually on an engine fitted with idle speed control valve as this will slowly return the engine back to base idle as an anti-stall characteristic. This function normally only affects the engine speed from around 1200 rpm back to the idle setting.
A time base of approximately 2 seconds plus is used, this enables the operator to view the AFM’s output voltage on one screen, from idle, through acceleration and back to idle again. The ‘hash’ on the waveform is due to the vacuum change from the induction pulses as the engine is running.
汽車診斷 | 汽車診斷儀 | 汽車故障診斷儀 | 汽車測(cè)試儀 | 汽車分析儀 | 汽車診斷示波器 | 汽車電路測(cè)試儀 | 汽車電路分析儀 | 發(fā)動(dòng)機(jī)分析儀 | 發(fā)動(dòng)機(jī)綜合分析儀 | 發(fā)動(dòng)機(jī)檢測(cè)中心 | 點(diǎn)火分析儀 | 點(diǎn)火測(cè)試儀 | 汽車傳感器測(cè)試儀 | CAN總線示波器 | LIN總線示波器 | 汽車故障記錄儀 | 汽車傳感器分析儀 | 汽車檢測(cè)儀 | 噴油嘴測(cè)試儀 | 點(diǎn)火線圈測(cè)試儀 | 蓄電池測(cè)試儀 | 發(fā)電機(jī)測(cè)試儀 | 起動(dòng)機(jī)測(cè)試儀 | ABS傳感器測(cè)試儀 | ECU測(cè)試儀 | ECM測(cè)試儀 | 進(jìn)氣真空/壓力測(cè)試儀 | 排氣壓力測(cè)試儀 | 汽車技術(shù)培訓(xùn) | 爆震傳感器測(cè)試儀 | 缺火測(cè)試儀 | 缺缸測(cè)試儀 | 線路測(cè)試儀 | 引出線 | 汽車數(shù)字示波器 | 真空傳感器 | 高壓感應(yīng)測(cè)試頭 | 無分電器點(diǎn)火測(cè)試頭 | 獨(dú)立點(diǎn)火（COP）感應(yīng)測(cè)試頭 | 漏電測(cè)試儀 | 氣缸相對(duì)壓縮測(cè)試 | 電腦測(cè)試儀 | 發(fā)動(dòng)機(jī)控制器測(cè)試儀 | 泄漏測(cè)試儀 | 熒光檢漏 | 超聲波檢漏 | 汽車數(shù)字萬用表 | 電流鉗表 | 電流勾表 | 點(diǎn)火正時(shí)燈 |
