The 280-FP Flow Probe is a highly accurate water velocity instrument for measuring flows in open channels and partially filled pipes. The water velocity probe consists of a protected water turbo prop positive displacement sensor coupled with an expandable probe handle ending in a digital readout display. The water flow meter incorporates true velocity averaging for the most accurate flow measurements. The flow probe is ideal for storm water runoff studies, sewer flow measurements, measuring flows in rivers and streams, and monitoring water velocity in ditches and canals.
The flow probe incorporates the unique Turbo-Prop Propeller Sensor, which uses the most accurate positive displacement technique available for velocity sensing. The turbo-prop is designed to shed debris and is protected inside a 2" diameter housing. The probe housing may be placed directly on the bottom of a pipe or streambed for measuring low flows down to 2" in depth. The flow meter propeller rotates freely on its bearing shaft with no mechanical interconnections for minimal friction. Magnetic material in the propeller tip passes a pickup point in the water velocity meter handle producing electrical impulses that are carried to the readout display by an internal cable. The turbo-prop is easily removed for cleaning or replacement.
The Water Velocity Computer receives an electrical signal from the propeller, amplifies the signal, and converts the reading to feet per second (or meters per second, depending on programming). The large LCD screen displays average, minimum, and maximum water velocity readings. Up to 30 sets of minimum, maximum, and average data readings can be stored in the water velocity computer. These data points can be reviewed on the computer screen for later analysis. The water velocity computer has a water-resistant housing and incorporates a unique four-button operation for changing functions and resetting the display. The water velocity computer is powered by a non-replaceable battery that will last approximately five years with normal use. Low battery warnings will also display as appropriate.
The Flow Probe Handle can telescope from 3.7 feet to 6 feet in length (FP111), 5.5 feet to 14 feet (FP211), or 2.5 feet to 5.5 feet (FP311). The handle is constructed of anodized aluminum for light weight and long life. The 15 foot length of the FP211 Flow Probe allows for measuring sewer flows from street level and measuring stream flows from low bridges, while the 2.5 foot collapsed length of the FP311 Flow Probe is ideal for carrying into remote flow monitoring areas. A 3 foot (1.7 foot for the FP311) mylar coated staff gauge (graduated in hundredths of a foot and centimeters) is attached to the lower section of the water velocity probe for instant water depth measurements and accurate propeller positioning.
The flow probe can be used to measure the True Average Water Velocity of a channel's flow. As long as the turbo-prop sensor is in the water flow, the computer will average the water velocity. One reading is taken per second, and a continuous average water velocity is displayed. To obtain the true average velocity the flow probe should be slowly moved throughout the cross sectional area being measured. Once the reading becomes steady, the true average water velocity of the cross sectional area is obtained. This allows for highly accurate flow measurements, which average the differences in velocities that occur throughout a flow's cross-section and with water surges over time. The average water velocity can be saved by pressing the SAVE button and reviewed later.
The Flow Probe Swivel Head option allows you to rotate the flow probe's turbo prop to +90 degrees from its standard position. This option lets the flow probe take water velocity measurements in hard to measure areas such as vertical pipes on water tanks or swimming pool drainage systems.
Significant errors can occur when measuring water flow other than directly parallel to the direction of flow. The Flow Probe Alignment Fin is designed to help orient the flow probe parallel to flow when the end of the probe can't be seen well due to the depth or cloudiness of the water. To use this accessory, immerse the flow probe and rotate it back and forth until the least amount of resistance is felt due to the water flowing past the alignment fin.