Originally, thermographs (later replaced with data loggers and thermistors) were installed at each stream site to continuously monitor stream temperature with an adjacent air temperature site near the stream. Stream temperature probes are generally anchored near the stream bottom. Air temperature was generally measured at 1 meter above the forest floor and insulated originally with an A-frame shield (later replaced with pvc-constructed shields). Many of the probes were repositioned in the early 1990's at 1 meter above average winter snow level. Generally, sites are visited and charts/CR10 records collected on a monthly basis. In 1987, Campbell Scientific CR-10 data loggers replaced 8 circular chart installations at the original sites. Early Lookout Creek stream temperature data 1950-1981 was collected by the USGS.
The original thermograph instrument was the Dual Recording Thermometer Model RFHTT. This instrument records temperatures from two separate locations (air and soil) simultaneously on a single chart. Each of the two thermometer mechanisms operate with a mercury-filled sensing bulb which expands or contracts in response to temperature changes and in turn moves the recording pen along the calibrated chart. To prevent interference between the two pens, the right-hand pen records 1/12 revolution behind the left-hand pen. The recorder uses 10 inch 30- and 31-day Partlow circular charts that have ranges from -30°F - 170°F or 20°F - 120°F.
These original thermograph charts were replaced with Campbell Scientific data loggers ( typically CR10, CR21X, CR500, or CR23X) beginning in 1987. The temperature probes used with the data loggers were type T thermocouple soldered from thermocouple wire. These thermocouple wires have gradually been replaced through the late 1990-s with Campbell Scientific model 107 temperature probes (CS107B or CS107B-L) which include the Fenwal Electronics UUT51J1 thermistor.
A description of sites and measurement history is here: