EQUIPMENT AND SUPPLIES: Water-Quality Field Instrumentation

                                               October 14, 1975


Subject: EQUIPMENT AND SUPPLIES: Water-Quality Field

The Water Quality Advisory Committee at its last meeting 
recommended that the Quality of Water Branch periodically advise 
the operational program of field instruments that are considered 
to be the best, based upon field experience within the Water 
Resources Division. Criteria on which the evaluations should be 
based include ease of maintenance, calibration, and operation; 
reliability; accuracy; and precision. In consideration of the 
criteria, the following instruments are highly recommended for use 
by WRD personnel:

Dissolved oxygen--Yellow Springs Instrument (models 54 and 57).
pH--Leeds and Northrup (model 7417), Beckman model 100900),
    Fisher (model 150), Orion (model 301), Sargent-Welch 
   (model PBL). 
pH electrode--Sargent-Welch combination. 
Specific conductance--Lab-line (model Mark IV) and Beckman 
   (model RB3).

The above list does not imply official endorsement of any 
particular instrument by the Geological Survey, nor does it imply 
that the listed instruments are the only ones that should be used 
in the Division's field activities. We realize that there are 
other instruments which can be used effectively in the field; 
however, the above came out on top by concensus of the Branch 
staff and the Regional Water-Quality Specialists.

Because the Branch will be revising these recommendations 
periodically, you are encouraged to relay your experiences and 
observations of field instruments to the Chief, Quality of Water 
Branch, through your Regional Water-Quality Specialist.

                               R. J. Pickering

WRD Distribution: A, B, FO, PO