u/abderrezak_mo

Hi everyone,

I’m currently working on a power meter project and designing the hardware myself. I ran into a situation that I’d really appreciate some insight on.

For phase-to-phase voltage measurement, my circuit works fine. But when adapting it for phase-to-neutral measurement, I reused the same design and connected neutral as the reference (GND) for my board.

Here’s the issue:

When I measure between phase and neutral at the circuit breaker with the phase disconnected, I still see around ~10V on the neutral. This makes me concerned because if I tie neutral directly to my board GND, that means my whole circuit (including the microcontroller) could sit at around 10V relative to earth.

My questions:

Is this ~10V on neutral something normal (maybe due to leakage or induced voltage)?

Is it safe to use neutral as GND for my measurement circuit?

Can I use a voltage divider on the neutral before referencing it to my board GND (similar to what I did for phase measurement)?

Or should I redesign this using isolation (like a transformer or isolation amplifier)?

I want to make sure my design is both safe and reliable, so any guidance or best practices would be really helpful.

Thanks in advance!

Hi everyone,

I’m currently working on a power meter project and designing the hardware myself. I ran into a situation that I’d really appreciate some insight on.

For phase-to-phase voltage measurement, my circuit works fine. But when adapting it for phase-to-neutral measurement, I reused the same design and connected neutral as the reference (GND) for my board.

Here’s the issue:

When I measure between phase and neutral at the circuit breaker with the phase disconnected, I still see around ~10V on the neutral. This makes me concerned because if I tie neutral directly to my board GND, that means my whole circuit (including the microcontroller) could sit at around 10V relative to earth.

My questions:

Is this ~10V on neutral something normal (maybe due to leakage or induced voltage)?

Is it safe to use neutral as GND for my measurement circuit?

Can I use a voltage divider on the neutral before referencing it to my board GND (similar to what I did for phase measurement)?

Or should I redesign this using isolation (like a transformer or isolation amplifier)?

I want to make sure my design is both safe and reliable, so any guidance or best practices would be really helpful.

Thanks in advance!

Hi everyone,

I’m currently working on a power meter project and designing the hardware myself. I ran into a situation that I’d really appreciate some insight on.

For phase-to-phase voltage measurement, my circuit works fine. But when adapting it for phase-to-neutral measurement, I reused the same design and connected neutral as the reference (GND) for my board.

Here’s the issue:

When I measure between phase and neutral at the circuit breaker with the phase disconnected, I still see around ~10V on the neutral. This makes me concerned because if I tie neutral directly to my board GND, that means my whole circuit (including the microcontroller) could sit at around 10V relative to earth.

My questions:

Is this ~10V on neutral something normal (maybe due to leakage or induced voltage)?

Is it safe to use neutral as GND for my measurement circuit?

Can I use a voltage divider on the neutral before referencing it to my board GND (similar to what I did for phase measurement)?

Or should I redesign this using isolation (like a transformer or isolation amplifier)?

I want to make sure my design is both safe and reliable, so any guidance or best practices would be really helpful.

Thanks in advance!

Hi everyone,

I’m currently working on a power meter project and designing the hardware myself. I ran into a situation that I’d really appreciate some insight on.

For phase-to-phase voltage measurement, my circuit works fine. But when adapting it for phase-to-neutral measurement, I reused the same design and connected neutral as the reference (GND) for my board.

Here’s the issue:

When I measure between phase and neutral at the circuit breaker with the phase disconnected, I still see around ~10V on the neutral. This makes me concerned because if I tie neutral directly to my board GND, that means my whole circuit (including the microcontroller) could sit at around 10V relative to earth.

My questions:

Is this ~10V on neutral something normal (maybe due to leakage or induced voltage)?

Is it safe to use neutral as GND for my measurement circuit?

Can I use a voltage divider on the neutral before referencing it to my board GND (similar to what I did for phase measurement)?

Or should I redesign this using isolation (like a transformer or isolation amplifier)?

I want to make sure my design is both safe and reliable, so any guidance or best practices would be really helpful.

Thanks in advance!