H40 – Wave Probe System


H40 – Wave Probe System

A simple and robust system for the measurement and recording of water wave profiles, which uses the principle of measuring the electrical conductivity between two parallel wires.


A simple and robust system for the measurement and recording of water wave profiles, which uses the principle of measuring the electrical conductivity between two parallel wires.

The system is available in 1, 2 or 3 channel form and can display data by high speed recorder or input to a data logger. Alternative lengths of probe are 300mm or 500mm.

No additional modules or test instruments are required

Each probe consists of a pair of stainless steel wires which dip into the water waves. The electrical conductivity between them is measured, and is linearly related to their depth of immersion hence to wave height. The method is free of meniscus and `wetting´ effects.

The result is a system giving high dynamic accuracy over a wide range of wave heights and frequencies.

Energisation is conducted by means of an audio frequency drive signal which avoids all polarisation effects at the wire interface. The signal is balanced relative to earth, to render the system immune to common mode voltages between the water and instrument earth. The frequency can be altered to permit two or more sensors to operate in close proximity without mutual interference.

The probe consists of two 1.5mm diameter stainless steel wires spaced 12.5mm apart & 300mm long or 500mm long as required.

Each probe is connected to its own wave monitor module in the electronic console by a twin core flexible cable 10m long. The distance between the console and probe may be increased up to 100m using commonly available low current cables.

The wave monitor module provides output signals to drive a chart recorder or for input to a data logger (both to be supplied by the user). The records enable wave height, frequency and profile to be observed. Wave velocity can be measured by means of two sensors, spaced a known distance apart, each giving a recorder trace via its own monitor module.

The module incorporates a unique system of compensation for the resistance of the probe connecting cable which ensures that the characteristic of the probe remains linear, even for large dynamic ranges.

The compensation is set up quickly and easily by disconnecting the cable at the probe end and plugging it into two additional sockets on the module panel, and then adjusting a preset potentiometer.

A ‘Datum’ control enables the output from the module to be set to zero for any chosen depth of probe immersion.

Technical Specifications

Not suitable for use in salt water

Twin Wire Probe:

  • Construction: Hardened stainless steel with conical ends
  • Range of wave heights: Synthetic sapphire vee jewels
  • Temperature coefficient: 2% of span per 1ºC change in water temperature. The wave monitor module incorporates a control for easy calibration and resetting. Supplied with holder allowing calibration of the probe in steps of 10mm up to a maximum of 170mm

The system incorporates a power supply module. Alternative power supplies are available for operation from ac mains (refer to specification summary).

  • Input (ac mains): 220/240V, 50Hz or 120V/60Hz
  • Consumption: 700mA nominal on full load
  • Output: ±15V dc regulated with short-circuit protection

Wave Monitor Module:

  • Input connections: Two 4mm sockets on front panel or via back wiring for sensor. Two 4mm sockets on front panel for
  • Voltage output: ±10V max., centre zero, via BNC coaxial connector on front panel or via back connector max. load 10mA
  • Current output: ±10mA max., centre zero, via back connector source impedance 1k
  • Indicating meter: Centre zero for adjustment of datum. 10 turn potentiometer with calibrated dial for adjustment of output voltage. Single turn preset potentiometer for adjustment of cable compensation.
    Frequency response: 10Hz (to 95% output)
    Frequencies: 4kHz, 5kHz, 6kHz, 7kHz, 9kHz, 10kHz
    Phase lag: 17º (at 95% output)
    Energisation: Nominal values

Features & Benefits


  • Easily set up and calibrated
  • High dynamic accuracy
  • Linear calibration over a large range
  • Outputs for high speed recorders and data loggers
  • Can be operated at different energisation frequencies to avoid mutual interaction between two or more closely spaced probes
  • Supplied as a complete working system, with the option of 1, 2, or 3 channels of measurement


Product Volume    Gross Weight    Power Supply Key

H40-1-1-A/B/G              0.1m3                   10kg
H40-1-2-A/B/G              0.15m3                 20kg
H40-1-3-A/B/G              0.17m3                 30kg
H40-2-1-A/B/G              0.1m3                   10kg
H40-2-2-A/B/G              0.15m3                 20kg
H40-2-3-A/B/G              0.17m3                 30kg

  • H40-1-1-A
  • H40-1-2-A
  • H40-1-1-B
  • H40-1-2-B
  • H40-1-1-G
  • H40-1-2-G
Armfield Updates

Subscribe to our occasional newsletter for the latest product updates from Armfield Engineering.