Dynamax HPFM3, Installation And Operation Manual, Page: 55 / 86

Revision: JUNE 2017 55
7.0 Raw Data for K, and Temperature Corrections
7.1 Temperature Corrections with the Built in Sensor
The calibration factors used to convert dP to flow are temperature dependent, because KCT is inversely proportional to
the viscosity of water and the viscosity of water changes about 2.3% per oC (Tyree et al 1995). The HPFM will be supplied
with calibration curves and the temperature at which the calibration was done.
During lab measurements the HPFM and sample are often at nearly the same temperature, but in the field the HPFM
and sample can be at different temperatures, e.g. 5 to 10 oC different, if one is in the sun and the other is in the shade.
The best practice is to keep both the HPFM and sample shaded to ensure similar temperatures. If the sample is wet,
the evaporation can also lower the temperature below the air temperature.
7.2 Corrections At Test Temperature
HPFM Gen 3 has a built in sensor attached to the outlet manifold, which records and logs temperature with all
the flow and pressure data during calibration. The data collected with all measurements are recorded in real
time always. The conductance values are adjusted by the following formula:
Kcorrected = K (0.554 + 0.0225 T)/(0.554 + 0.0225 T*)
Where:
K = the uncorrected conductance,
T = the temperature at which K was measured, and
T* is the temperature at which the HPFM was calibrated. The resistances could be corrected as well by the user.
by the following formula:
Rcorrected = R (0.554 + 0.0225 T*)/(0.554 + 0.0225 T)
Shown below is the example of the K, K corrected and the K25 calculated conductance results from a QSS reading.
The formulas above correct K- and R-values
to the temperature at which the sample was
measured.