Agree with Gabriel.
Also, it is possible that you have damaged something by not looking into all the parameters in the first place before connecting AC to something that is DC. This may account for the fluctuations you experience with the tester. You should be using the final CT product in your testing, not something that is different.....it's not much of a durability test if it isn't the product you're going to be using. Finally, ensure that you have all the wiring as recommended in the install literature.