RO testing and Soft Water Test

I am trying to find out how to tell if the RO machine is working properly. I found my soft water is 2 grains which the Manufacturer says in to high and I need to Iron Out the bed and set the hardness in at +5
I found the RO water to be O grains so it is working but how do you tell if it is working WELL. I feel my spot free cycle is leaving to many spots on the windshields :( Any advice would be appreciated. This is a 6 bay SS about 7 years old. Thanks

You need a TDS meter. Most measure parts per million, below 50 will leave some spots, but is generally acceptable however 30 and below is what to shoot for. If it’s above 70 or so most likely the membranes in the RO are shot.

http://cgi.ebay.com/TDS-PPM-Meter-Hydroponic-Water-Quality-Tester-NEW-NIB_W0QQitemZ260371456423QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item260371456423&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

This one is $10

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Got the tds meter, 15 bucks ebay :) new. Now my soft water is reading O grains soft with the test kit and the RO water reads 265 with the new tps meter, is my membrane toast, I dont know how old it is, we inherited it with the wash. I am happy with there soft water machine though, it read 1-2 grains but with a rust out treamment and extra reineration and setting it up 5 on hardness it now test O grains. Any thing beside the Memebrane that could be the problem.???
PS< I dont know what I would do with out you guys :) Thanks for the help.