Ground testing using a labscope.
I often get the question of how much of a voltage drop is acceptable for a given circuit. Years ago I learned a spec of 30-50mV per amp of current flowing in the circuit. After testing lots of grounds of the years I found this spec to be very good.
I also use a scope to test grounds while doing a ?Wiggle? test of harness and connections. The MODIS/Vantage Pro has a nice long record depth to make this much easier.
Now when testing sensor reference grounds I do not use the Voltage drop method of checking them. They are extremely low current circuits (so they don?t create an accurately measurable voltage drop) so an ohmmeter is preferable for checking ground circuit integrity.
And while we are talking about sensor grounds many sensor grounds today are not at battery negative potential (Key off or KOEO) or engine block ground KOER. Many sensor grounds, sometimes referred to as sensor low or reference low, are ?floated? above engine ground so don?t be surprised to see some voltage potential offset in those circuits.
Below is a capture of a bad alternator ground circuit found during a wiggle test. Channel 3 shows the noise created by the alternator ground being loose. Look at the cursor readings for channel 3.
Happy hunting
I often get the question of how much of a voltage drop is acceptable for a given circuit. Years ago I learned a spec of 30-50mV per amp of current flowing in the circuit. After testing lots of grounds of the years I found this spec to be very good.
I also use a scope to test grounds while doing a ?Wiggle? test of harness and connections. The MODIS/Vantage Pro has a nice long record depth to make this much easier.
Now when testing sensor reference grounds I do not use the Voltage drop method of checking them. They are extremely low current circuits (so they don?t create an accurately measurable voltage drop) so an ohmmeter is preferable for checking ground circuit integrity.
And while we are talking about sensor grounds many sensor grounds today are not at battery negative potential (Key off or KOEO) or engine block ground KOER. Many sensor grounds, sometimes referred to as sensor low or reference low, are ?floated? above engine ground so don?t be surprised to see some voltage potential offset in those circuits.
Below is a capture of a bad alternator ground circuit found during a wiggle test. Channel 3 shows the noise created by the alternator ground being loose. Look at the cursor readings for channel 3.
Happy hunting
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