Hello all,
My customer is probing the voltage between the two motor terminals. The scope ground is connected to the negative lead (MTR-) and the probe tip is connected to (MTR+). The scope (old Agilent 54622A) displays the waveform just fine. However, it introduces lots of noise into the system. Without the scope ground on MTR-, the system functions just fine with the usual motor noise.
The motor controller is a low-side PWM driven type, where MTR- switches from the system ground to ~330V.
The motor controller is floating and not connected to the earth. The scope itself is not connected to the earth either.
Even though connecting the scope ground to a switching node seems bad, I cannot explain how the noise is introduced to the system. Could anyone show some light on how the extra noise is introduced when the scope ground is connected to MTR-.
Thanks in advance.
My customer is probing the voltage between the two motor terminals. The scope ground is connected to the negative lead (MTR-) and the probe tip is connected to (MTR+). The scope (old Agilent 54622A) displays the waveform just fine. However, it introduces lots of noise into the system. Without the scope ground on MTR-, the system functions just fine with the usual motor noise.
The motor controller is a low-side PWM driven type, where MTR- switches from the system ground to ~330V.
The motor controller is floating and not connected to the earth. The scope itself is not connected to the earth either.
Even though connecting the scope ground to a switching node seems bad, I cannot explain how the noise is introduced to the system. Could anyone show some light on how the extra noise is introduced when the scope ground is connected to MTR-.
Thanks in advance.