I am looking for recommendations on a simple to use DO meter with depth and temp. to use at the ponds. Would like a small battery powered unit that does not require calibrattion. Just turn on and lower the probe to depth and take reading. I am not interested in the $1500 type nor do I want the $ 50 pseudo-type that works on temp and water clarity. I would like a real , easy to use meter. I would be greatful for any suggestions on what has worked well for you. ewest