Increased Thermal‐Pulse Flowmeter Resolution by Adding a Packer and Computer
1994
Lyles, Brad F.
Measurement accuracy was increased by nearly one order of magnitude by outfitting the thermal‐pulse flowmeter (TFM) with an inflatable packer. To accurately measure slow water velocities in boreholes greater than 15 cm diameter, it is necessary to divert borehole fluids through the TFM by inflating a packer. During calibration it was noted that the TFM's accuracy decreased as the borehole diameter increased. With Lhe packer inflated the TFM has a useful flow measurement range of 0.08 to 15 L/min (with flow velocities of 0.24 ± 0.012 cm/inin to 45.7 ± 0.61 cm/min, respectively, in 20‐cm‐diameter pipe), compared to 0.8 to 57 L/min for a packcrless TFM. A computer interlace was added to the TFM to provide a real‐time graphical display of the differential voltage output from the TFM, a running mean and standard deviation of the pulse‐response time, and a mean flow rate and velocity based on calibration curve fits.
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