What was the reason that TA018 was better than the TA189. I would say the TA018 would actual be worse, for low mA readings.Accuracy-TA189
± 1% of reading ± 2 mATA018
± 1.5% of reading ± 5 mA
The cost difference is due to the TA189 having better performance and accuracy.
If you are using one these clamps, I would wrap say 10 turns of the conductor around the clamp. Then divide the reading by the number of turns, this will give a better accuracy as you are measuring a higher current.
If you need better accuracy I would look buying one these to use with a scope or meter-http://www.eevblog.com/projects/ucurrent/