SWT’s Auto Calibrate feature applies an in-situ correction to the flowmeter’s transit-time measurement by adjusting the internal transit-time to align with a user-specified liquid sound speed during setup. This function is intended to reduce small systematic errors in the inferred acoustic path timing and thereby improve overall flow measurement accuracy.
When Auto Calibrate is enabled, the calibration routine begins immediately after the user exits the Setup Menu which forces the device to write configuration parameters to the flowmeter. Once initiated, the routine remains active for one minute. During this interval, the instrument uses the specified liquid sound speed as a calibration reference and iteratively refines the transit-time solution. At the end of the calibration period, the measured sound speed should converge closely to the specified reference value, indicating that the transit-time measurement has been optimized for the installed condition.
The resulting calibration coefficients are stored in non-volatile memory and become part of the permanent flow calculation unless overwritten by a subsequent setup change or recalibration event.
Auto Calibrate is most effective for correcting small systematic offsets associated with acoustic wavefront detection, signal timing discrimination, and uncertainty in the estimated transit time through the pipe wall, liner, or other non-liquid portions of the acoustic path.
Because this function forces the meter’s acoustic timing solution to agree with a specified liquid sound speed, it should only be used when that reference value is known with high confidence. Water is a good candidate because its sound speed is well characterized as a function of temperature. If the actual liquid sound speed is uncertain, poorly characterized, or variable over time, Auto Calibrate should remain disabled. Applying an incorrect reference value can bias the transit-time solution and reduce overall measurement accuracy.
Auto Calibrate can be enabled or disabled in the Advanced Setup menu of the Orcas App, Thermal Energy Meter (TEM), or Flow Computer.
