WCM-3000 Robust Water Content System

General DescriptionMulti Element System

     The SEA Model WC-3000 Robust Water content System was designed to provide aircraft and wind tunnel users  with a single, rugged sensor to measure  Total Water Content (TWC). The instrument consists of one heated stainless steel element. The element is directly heated by low voltage dc current flowing through the element. The element is maintained at a constant temperature, typically 140 °C, by a digital, closed loop, control system.

   Given the dimensions of  the element and the true airspeed of the airflow the power level set by the control system to maintain temperature can be converted directly into the water content of the air stream.

    The instrument uses a scoop shaped sensor to collect both liquid water  (LWC)  and  ice crystals ( IWC).  The combined total of LWC and IWC is referred to as Total Water Content (TWC).  

         In addition to temperature control for the heated element, the deice system is  also  temperature controlled.  During operation the deice power is adjusted to maintain the instrument housing at a constant 50 °C, which is comfortably warm to the touch. Maintaining the instrument housing  at a constant temperature provides a  stabilized thermal environment around the sensing elements which leads to improved LWC and TWC measurement accuracies.

    Temperature control of  the heated elements and the deice heaters allows the unit to be operated safely and continuously at zero airspeed.

   The system consists of three major components, the sense head, the power box and the control unit.  The sense head is mounted in the air stream.  The power box  is mounted near the sense head.  The control unit is mounted where it is convenient for the user.  

      The power box for the Robust Head can be redesigned to fit within a standard PMS or DMT canister. 

      The control unit can be built in many different packages from a standard 19" rack unit that is 4U high to a Zeus rail unit that is 6" x 6" x 10" deep. The control unit can also be imbedded in SEA's M300 DAS.


Operating Manual


FeaturesRobust TAS vs WC



see endnote [2]

0 - 10  gms/m3 TAS <  150 m/s
SL – 45,000 ft @ -40°F

0 - 6  gms/m3 TAS < 230 m/s
SL - 45,000 ft @ -40°

Airspeed Range
0–275 m/s, ( 0–533 kt)
Measurement Range
10–275 m/s, (20–533 kt), see endnote [1]
Power Supply Range
18–32 vdc, 28 vdc nominal

Power Consumption

see endnote [3]

3.5 amp minimum

11 amp typical

49 amp maximum

Sensor Head Dimensions

3.05 “ x .46 “  x .95” external
5.45 “ x 3.25 “  x 3.25” overal

Power Control Box Dimensions

15.2” x 7.8” x 3.5”*
*can be made smaller if required            

Sensor Head Weight
1.2 lb
Power Control Box Weight
12.0 lb
Total Weight (Excluding Cables)
13.5 lb
Data Output

R3-232/422 ASCII Serial Data. 9600 – 115,200 baud or Ethernet Network


Data Update Rate
Selectable 1 to 20 updates/second

1 - “Safe Operation” means that the instrument can be left fully powered on continuously at zero airspeed without damage.  However as the airspeed is reduced to zero, the effective sample volume decreases to zero and the measurement of LWC is not possible.  Depending on the specifics, some minimum airspeed is required to establish a minimum acceptable sample volume. Please contact SEA for details about measurements at very low speeds.

2 - Refer to graph for details.  Maximum possible LWC/TWC varies slightly with altitude and is about 10% greater at sea level compared to 40,000 ft at the same airspeed.

3 - Power supply current varies with airspeed, altitude, ambient temperature and water content.  Supply currents include deice power.  Minimum current is for zero airspeed at 20 °c. Typical current is for 67 m/s, -9 °c, 1.5 gm/m3.  Maximum current is for maximum possible LWC/TWC.