As a vibration consultant, my choice of instruments is based on two factors, price and performance. The VB2000T does a great job at a great price.
http://www.reliabilitydirect.com/vibrationmeterproducts/vb1.htm
Speaking as a guy that does alot of balancing, perhaps I can offer some advice. Your choice of instruments is good, I have a VB-2000T myself and they work great.
I am guessing you are trying to balance at the sheave because the vibration amplitudes are highest here. It may be unbalance, but...