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    Thread: Anyone has an oscilloscope that I can use?

    1. #1
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      autohead's Avatar
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      Anyone has an oscilloscope that I can use?

      Bought this 0 56 Digital Red LED Frequency and Tachometer Rotate Speed Meter Two Function | eBay and surprisingly for a China make it has pretty good accuracy. Checked it by connecting it's inputs to system audio and used Audacity to generate square waves. The accuracy is to 1 decimal.
      Now I am trying to source an input from my car ignition and damn, it looks like it is not displaying the rpm properly. I made sure I divider to 3. Connected to ignition -ve first and to the wire from ECU that goes to the ignition control module but no use. I am suspecting that there is lot of noise in both the places and that I may need to filter the signal before input to this tach.

      However I don't even know if the input to the ign control module is even a square wave, and how much noise might it present. Appreciate if anyone who has could let me use it or else give some pointers on it.

    2. #2
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      Are you trying to use this as a tachometer?

      Ignition signals are generally very noisy. I'd use an Opto Coupler to isolate these two domains.

      Another generic way is to use inductive (with schmitt trigger to clean up) or optical/Hall effect pickup from one of the rotating pulleys and correlate accordingly.
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      It has tachometer mode also. Check it with 1hz and it displayed 60 as the RPM.

      There is a Camshaft Position sensor in the distributor. I guess it is a Hall effect one. The description in the service manual implies that the resistance of that sensor changes according to the rotating shaft. Since the all the sensors run off of 5V, can this be a clean source of input? If so can a comparator with an op amp do it?

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      Quote Originally Posted by autohead View Post
      I guess it is a Hall effect one.
      If you can post the part number or datasheet of the sensor, we can discuss of ways to interface it. There are just too many types of HE sensors (varying state and output) though the basic detection principle is similar.
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      Can you PM me your number please? I would love to talk to you.

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