PROGRAMS AND PLANS--Quality Assurance of Temperature Measurements In Reply Refer To: September 28, 1979 EGS-Mail Stop 412 QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 79.16 Subject: PROGRAMS AND PLANS--Quality Assurance of Temperature Measurements This is to remind you that it is the field office's responsibility to assure that only accurate thermometers are used to make temperature measurements in the field and in district laboratories. Frequently new thermometers are found to be in error when checked against ASTM standard thermometers. Thermometers that are used in making general temperature measurements should be accurate to +/- 0.5 degrees C. They should be calibrated before they are used and periodically during their usage. TWRI Book 1, Chapter Dl should be referred to for proper procedures to follow in calibrating thermometers. Although the method described on page 28 requires two constant-temperature water baths, other stable reference sources may be used. A mixture of water and ice agitated by a magnetic stirrer makes a good low temperature reference solution and an insulated container of water at room temperature makes a good second calibration point. Thermometers that read within + 0.5!C of an ASTM standard thermometer at two reference calibration points are acceptable for field use. It is advisable to mark these thermometers as acceptable. A dot or ring of paint or finger nail polish on the thermometer has been found to be satisfactory for this. Thermometers that are unacceptable should be destroyed or returned to the supplier for replacement. Many of the electronic field instruments have a thermister system that can be Used to make temperature measurements. These systems should also be checked frequently at several points over their operating range to assure proper operation. Units that do not perform to the manufacturer's specifications or to +/- 0.5 degrees C should not be used or returned to the manufacturer for repair or adjustment. Remember that it takes both good equipment and proper technique to make a valid temperature measurement. TWRI Book 1, Chaper Dl is an excellent source of information on this subject, and all field personnel should be familiar with it. R. J. Pickering WRD Distribution: A, B, S, FO, PO