 |
This is a good waveform |
 View larger image
 Download this waveform file for use with PicoScope
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 | 汽車測試儀 | 汽車分析儀 | 汽車診斷示波器 | 汽車電路測試儀 | 汽車電路分析儀 | 發動機分析儀 | 發動機綜合分析儀 | 發動機檢測中心 | 點火分析儀 | 點火測試儀 | 汽車傳感器測試儀 | 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 | 汽車檢測儀 | 噴油嘴測試儀 | 點火線圈測試儀 | 蓄電池測試儀 | 發電機測試儀 | 起動機測試儀 | ABS傳感器測試儀 | ECU測試儀 | ECM測試儀 | 進氣真空/壓力測試儀 | 排氣壓力測試儀 | 汽車技術培訓 | 爆震傳感器測試儀 | 缺火測試儀 | 缺缸測試儀 | 線路測試儀 | 引出線 | 汽車數字示波器 | 真空傳感器 | 高壓感應測試頭 | 無分電器點火測試頭 | 獨立點火（COP）感應測試頭 | 漏電測試儀 | 氣缸相對壓縮測試 | 電腦測試儀 | 發動機控制器測試儀 | 泄漏測試儀 | 熒光檢漏 | 超聲波檢漏 | 汽車數字萬用表 | 電流鉗表 | 電流勾表 | 點火正時燈 |
