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A String Pot or Draw Wire sensor are sensors used for vertical displacement material compression and creep monitoring.


The sensors are typically packaged in a NEMA rated enclosure with an extended wire attached to it allowing it to span from floor to floor in a building. Depending on the expected travel, different models are available. The compact size, wide variety of travel ranges and favorable price as compared to LVDTs make this sensor attractive in a variety of different applications. See ASTM publication Volume 41, Issue 4 (July 2013) titled Monitoring of Vertical Movement in Four-Story Wood-Frame Building in Coastal British Columbia for detailed information on how String Pots can be used to monitor vertical displacement and compression of buildings.


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String Pot Sensor

    • NOTE: SPOT's use a specialised version of SMT data loggers, standard data loggers (DAQ's) are not compatiable
      • Existing Dataloggers can be modifed by SMT for use with the SPOT sensors
      • A3 adaptor boards are user changeable, allowing the A3 to be adapted to suit the sensors being monitored (Advanced users only)
    • 50mm Measuring Range used for floor to floor compression
    • 250mm Measuring Range used for full building and large scale monitoring
    • Mounted in NEMA rated enclosure with ½” conduit interface
    • Draw wire extensions available up to 300 feet
    • Different terminations and hook boxes are available depending on the mounting requirements
  • Specifications SPOT-00-50mm

    Measuring Range: 50mm

    Linearity (Conductive Plastic Pot P50):

    ≤ ±0.5% FSO (≤ ±0.25mm)

    Resolution (with A3/WiDAQ): 0.1mm


    Specifications SPOT-00-150mm

    Measuring Range: 150mm

    Linearity (Hybrid Pot P25):

    ≤ ±0.25% FSO (≤ ±0.375mm)

    Resolution (with A3/WiDAQ): 0.1mm


    Specifications SPOT-00-250mm

    Measuring Range: 250mm

    Linearity (Hybrid Pot P10):

    ≤ ±0.25% FSO (≤ ±0.25mm)

    Resolution (with A3/WiDAQ): 0.1mm


    FSO = Full Scale Output



    Operating Temperature: -20° to 80°C



    Material: Housing: Plastic 

    Draw wire: Stainless Steel

    Wire Mounting: Eyelet

    Housing: NEMA rated enclosure with grommet for analog wire

    Wire Acceleration: ~5g

    Wire Retraction Force (min): ~1N

    Wire Extension Force (max): ~2.5N


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