Ultrasonic circulation meters measure the degree in a channel by sending a pulse of audio from the face of the sensing unit to the surface area of the flow stream as well as measuring the moment for the resemble to return. The transportation time represents the distance between the face of the sensing unit as well as the surface area of the water.

When the meter is initially established up, a pre-determined range (or degree in some meters) is set. This range is either the absolutely no level (no circulation existing) or a specific degree in the flume or weir. With this preliminary calibration it is just an issue of straightforward math to establish the fluid level. This degree is after that related to either pre-programmed discharge formulas or strapping tables to result a flow rate.

Ultrasonic sensors have actually no scheduled maintenance since the sensing unit is not in call with the water. Ultrasonic sensors are not impacted by chemicals, grease, suspended solids, or silt in the WSL flow meters stream.

Efficiency of ultrasonic flow meters may be broken down by:

- Strong wind
- Solar home heating (of the sensor).
- Foam.
- Disturbance.
- Steam.
- False echoes from obstructions

To battle these problems a variety of techniques are used:

- Sensing unit sunshades (for solar home heating).
- Angling the sensor face (to decrease steam condensate develop).
- Exclusive control plans are used to change amplifier gain (to enhance resemble stamina).
- Variable blanking distances (to get rid of very early/ late echo returns).
- Wetting aspects (related to reduce heights as well as troughs in the outcome signal).

For optimal efficiency, ultrasonic circulation meters are not suggested for usage on networks much less than 6-inches [15.24 cm] wide (due to beam spread) or where heavy steam, foam, disturbance, drifting debris/ oil/ grease exist (although as seen over these conditions can in some cases be minimized).

To get optimal precision a temperature sensor [either important to the ultrasonic sensor (favored) or as a stand alone sensing unit] is called for to make up for modifications in air temperature level.

Dead period (the range determined from the face of the sensing unit in which sensing unit exhibits degraded efficiency) is commonly 1-foot [0.3048 m], while the array for flow dimension sensing units is normally up to 11-feet [3.353 m]

Under typical problems (still air, 40-70% family member moisture, 72 ° F [22.22 ° C], the degree dimension accuracy of ultrasonic flow meters can ± 1/4 to 3/8-inch [0.635 to 0.9525 centimeters] (relying on the change in level).

When mounting a ultrasonic sensing unit over a flume (or dam) there is a tradeoff in between ease of access (placing the sensor near the side of the flume) as well as maximum prospective precision (mounting the sensing unit over the centerline of the flume). Either problem is acceptable if the flow approaching the flume has been effectively conditioned as well as the flume effectively set. If, nonetheless, the flow has actually not been properly conditioned, is disturbance, or is inadequately distributed, analyses at the sidewall may differ from those in the center of the flume. Do not assume, however, that the centerline reading is immediately much more accurate.