Yes I have an resistor in parallel with it, and the value is matched with the CT so that the output voltage is in desire range.
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The spike is generated at the relay contact side rather than on the coil side in my case. Let me explain more. The CT is checking the current on the load of my circuit. However the load is not part of my circuit, it is normally a heater with a thermostat. Therefore when the heater is full or overheat, it will switch off automatically. I found that when this happen, my CT will generate some short impulse and it exceed the threshold of my comparator.