Engineering Report Appendix 4.

Ability of Each Device to Maintain A Constant Current Output

       The output current from each device was measured, first while stimulating into a 5K Ohm load and then while stimulating a 10K load in order to simulate a range of skin impedances. The table below shows the percentages of the changes in output between the two test loads at two intensites at each of three frequencies of stimulus. A constant current output across a range of impedances is critical for reliable and repeatable and standardized measures.
       The Neurometer® CPT/C demonstrated an ability to maintain a constant current output across all three frequencies when alternating between 5,000 Ohm and 10,000 Ohm loads with an average deviation in current output of 1.63%. The Medi-Dx 7000 did not demonstrate any ability to maintain a constant current output at any frequency when alternating between 5,000 Ohm and 10,000 Ohm loads with an average deviation in current output of 31.63%.

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Changes in Current Output Intensity When
Alternating Between 5K and 10K Ohm Loads

	Neurometer® CPT/C	Medi-Dx 7000
2000 Hz. @ 1.50mASetting	- 1.3%	- 26.1%
2000 Hz. @ 9.99mA Setting	+ 2.9%	- 31.5%
250 Hz. @ 1.50mA Setting	- 2.6%	- 32.7%
250 Hz. @ 9.99mA Setting	- 1.7%	- 31.5%
5 Hz. @ 1.50mA Setting	- 1.3%	- 24.1% and -32.8% (Asymmetric Output)
5 Hz. @ 9.99mA Setting	- 0.9%	- 27.7% and -35.1% (Asymmetric Output)