Objective
There has been some existing problems with the electrical reflex hammer. The occurrence of pressure build up with percussion and change of hammering points is one example. In order to make improvements on this device, we conducted studies with a newly designed percussion instrumental stimulator.

Method
The data collected from the first group was based on the manual percussion of electrical reflex hammer on the patella ligament. The data collected from the second group by usage of a newly designed instrumental stimulator maintained steady pressure and time and target position on the electrical reflex hammer. Comparisons were made between the two group.

Results
Our single measure of latency and amplitude on the manual and instrumental percussion group resulted in the reliability of 84.67%, 91.23%, 73.63%, and 83.29%. The 10 repeated measure of latency and amplitude on the manual and instrumental percussion group resulted in the reliability of 99.95%, 99.97%, 99.90%, and 99.94%.

Conclusion
From our experiment on the tendon reflex, we found out that it is important to have an instrumental stimulator that can maintain steady pressure while it is applying percussion to accurate data. On manual percussion, it is important to obtain data based on mean value of repeated measurements.