How to write a graduate study personal statement for a technical field without related bachelors degree?
I was recently accepted to a MS program that is different from my undergrad and graduate training.  In my personal statement I tried to relate my experience to the field I was pursuing.  I had field research experience in public health, but I was applying for a MS in biology.  I still used my research experience, but I focused on the general research skills that I developed, things that would be useful in the lab.  I mentioned things that are universal to all research.  

I think if you convey passion and direction for the new field, you'll be alright.  It can be an advantage too.  Think of ways you can incorporate your previous field if possible.  If not, show them your maturity and passion.  It seems like admissions committees can tell who is going through the motions and who is genuine.  Make your voice heard.