Current transformer inserts noise to the system

[alphacat]

My system comprises a current measuring unit.
Up to now I used a current sense resistor in order to measure load's current:
**broken link removed**
The resistor is connected to a Power Sensor IC.

I'd like to use a current transformer instead of the current sense resistor, so I disconnected the load and the sense resistor, and connected the transformer's output instead of the resistor:
**broken link removed**

In order to measure the Load's current, I inserted the LIVE wire of the LOAD into the transformer's loop.

When the LOAD (60W light bulb) was ON, the system behaved weird, It didnt respond when I pressed its button.
However, when the LOAD was OFF, the system responded to the button pressing.

It seems that the transformer somehow interrupts the system.
Perhaps it corrupts the ground? (The ground in my PCB is the Neutral wire)

What could be the reason for it?

Thank you.

 

[MikeMl]

Do you have the specified load resistor tied across the current transformer's secondary?

 

[alphacat]

The only "resistor" connected to the transformer's output (secondary coil) is the input resistance of the Power Sensor IC (which is about 30Kohm).

Why do you ask that?

 

[Nigel Goodwin]

The only "resistor" connected to the transformer's output (secondary coil) is the input resistance of the Power Sensor IC (which is about 30Kohm).

Why do you ask that?

Because you have to have the specified load resistance on the transformer.

 

[alphacat]

Oh I see.
Its a current transformer I took from a product I disassembled, since I wanted to see that I can integrate it into my system before I purchase one.
Therefore, I dont know its specified load resistance.
All I know is that in the product I took it from, the transformer's output was connected to an ADC.

What could happen if a non-matching load resistance is connected to the transformer's output?

 

[Hero999]

If the impedance is too high, the voltage will be too high and will increase with the frequency of AC current.

 

[MikeMl]

See Rburden in**broken link removed**

 

[eblc1388]

The only "resistor" connected to the transformer's output (secondary coil) is the input resistance of the Power Sensor IC (which is about 30Kohm).

With 30K as a load, the voltage across the CT secondary will be so high that the Power Sensor IC will probably be fried, unless its input has internal protection of some sort.

Maybe you have gotten lucky this time or may be not.