It is best to check our products at minimum scale and maximum scale for proper operation. If no current through the hole produces 0 VDC +/- 50 mV output, and 50 amps of current through the hole produce 5 VDC +/- 50 mV output, then the unit is calibrated properly. Your data shows a decreasing voltage output for higher current, which would be obviously incorrect. I will pass this along to our customer service department for a return material authorization or feel free to call or write us directly if you are short of time. Thank you.