Current transformers

Im using an a.c ammeter with a current transformer to moniter my primary
current to my pig the meter has multiple scales im using the 0-50 amp
scale (0-5amp full scale deflection) My question is what ratio of
current transformer to use ? Im using a 50:5 ratio current transformer
right know but i think the meter isnt reading the correct current. IT
says im drawing 20 amp with the welder on it lowest setting. I dont have
an a.c amprobe to see if this is corr  ect , Im going to invest in one
to investigate this matter further. Is the 50:5 ratio correct. My
current transformer is a instruments  transformer inc. cat.#2SHT500,
50-400 Hz, the arc welder is a Lincoln A.C. 225s, the transformer is an
Epoxy Cast High Voltage type 23,000Volts at  37.5K.V.A 
I have a dedicated circuit just for running tesla coils up to about
14KVa. wish I had more room. Any help would be appreciated. Thankyou