FLOW PROBE

A Flow Probe is a handheld instrument used to measure water velocity in open channels, streams, pipes, irrigation canals, and environmental monitoring sites. It typically consists of a telescoping rod with a protected propeller sensor (or electromagnetic sensor) at the end. The probe measures point velocity, which can be used to calculate discharge (flow rate) when combined with channel cross-section data.
Flow probes are widely used in hydrology, stormwater management, agricultural water distribution, wastewater monitoring, and environmental field studies.

Key Features

• • Direct reading of water velocity (often 0.1–20 ft/s or 0.03–6 m/s).
• • Telescoping handle for reaching into channels or culverts.
• • Protected propeller or EM sensor prevents debris interference.
• • Digital display showing real-time velocity, average velocity, and sometimes temperature.
• • Durable, waterproof construction for field use.
• • Low power operation (often AA batteries).

Common Types

1. Propeller Flow Probe (Most Common)

• • Small, multi-bladed rotor encased in a cage


• • Measures velocity via rotational speed


• • Good for streams, culverts, irrigation channels

2. Electromagnetic (EM) Flow Probe

• • No moving parts


• • Measures velocity using induced voltage in conductive water


• • Excellent for low-flow, debris-rich, or shallow water

3. Ultrasonic Flow Probe

• • Specialized instruments for pipe flow or large channels


• • Uses transit-time or Doppler ultrasound

Typical Specification

Applications

• • Stream and river flow studies


• • Irrigation canal monitoring


• • Drainage and stormwater system assessments


• • Environmental surveys and field hydrology


• • Wastewater treatment & industrial effluent monitoring


• • Culvert and pipe velocity measurement

Benefits to Users

• • Fast, portable, accurate velocity measurements
• • No need for large instruments or flow meters
• • Works in shallow or irregular channels
• • Rugged and suitable for field environments
• • Can be used to calculate stream discharge with cross-section data

Best Practices / Considerations

• • Take multiple depth measurements to compute average velocity (e.g., 0.4 depth, 0.6 depth).
• • Keep the probe aligned directly with flow direction.
• • Avoid contacting channel bed — can affect readings.
• • For low-clearance flows, EM probes are better than propeller probes.
• • Clean the sensor after use in sediment-heavy or debris-filled water.