Read Square Wave Signal with Voltmeter?

[stubuzz]

To troubleshoot my alternator I need to read the signals sent to and from the ECU to the smart charge regulator. These are 0-5v dc square wave signals. Now, the troubleshooting guide says that an oscilloscope is needed. However, can I get a reading with a digital volt meter?

I would give it a try, but the car is not running at the moment as a I am waiting for parts on back order. (Ford Thailand!)

[OneMoreFarang]

You should be able to see with a multimeter if there is any voltage/signal at all.

I.e. with a broken cable there would be nothing.

But that's about it. Multimeters have a different purpose. 

[stubuzz]

6 minutes ago, OneMoreFarang said:

You should be able to see with a multimeter if there is any voltage/signal at all.

Yes, I need to see that the ECU is is sending a voltage signal.

[OneMoreFarang]

2 minutes ago, stubuzz said:

Yes, I need to see that the ECU is is sending a voltage signal.

With the multimeter you should be able to see that is sends a voltage signal.

But the signal can obviously be "wrong". And that is what you don't see with a multimeter. 

[stubuzz]

4 minutes ago, OneMoreFarang said:

But the signal can obviously be "wrong". And that is what you don't see with a multimeter. 

Thanks. The square wave is a % duty cycle and that is what the alternator uses to determine the output charging rate. I don't really want to but a oscilloscope to diagnose this problem.

[digbeth]

an analog meter might be able to see the fluctuation between the +5 and -5v of a square wave

[bluejets]

On 7/11/2023 at 8:58 PM, stubuzz said:

These are 0-5v dc square wave signals.

No, multimeter will tell you nothing.

There is a small scope available for less than $40.

They work well, have used one here since the flood took out my other bench unit.

So well in fact I've never got around to replacing the former at all.

DSO150............

https://www.ebay.com.au/itm/385688686532

 

Mine gets used quite a lot so the only modification I did was to add a LiPo battery and usb charger.

 

There are online youtube videos on "how to use" and suggest a quick look at a couple of those as well.

Cheers.

 

 

Edited July 14, 2023 by bluejets