It has been amazing to see the DT of some of the tennis rackets that we have in for stringing, most of the rackets if the strings are intact do not read above the 35Ibs, that must really be hurting your arm!
Any way the Mini STT is a great tool for measuring the DT of the racket and to test your racket to see if the DT is within your playing range. I always keep mine in my tennis bag and freely test other players rackets on request!
I purchased my Mini SST from Tennis Tech