CM-3000™ Technical Specifications

In order to comply with FHWA regulations a true vertical clearances must be measured to any superstructure restriction. This means that the minimum vertical clearance must be measured from the roadway surface to the bottom of the structure in a single plumb line. The CM-3000™ uses an ultrasonic sensor for downward measurements and high speed ranging laser for upward measurements to provide a vertical clearance along one plum line. The two sensors within the CM-3000™ communicate with an integrated computer and electronic system that is housed on the side of the unit. The CM-3000™ then communicates to the users Panasonic Toughbook PC within the vehicle through the PC's Local Area Network (LAN) connection.  This combination of sensors allows the user to travel up to 75mph and collect a complete profile of the underside of a structure.  At 75mph, the CM-3000™ collects 7 data points per inch!

The CM-3000™ was designed with ease of installation and storage in mind. It is a complete, self contained package with no external parts (i.e. all components are attached to the unit). This results in no lost or misplaced components and assembly in three easy steps:

  1. Attach universal trailer hitch to test vehicle
  2. Slide unit on to mounting pole
  3. Connect cables and hit the road!

Class IIIa High-Speed Laser Sensor

The CM-3000™ uses a Class IIIa rangefinder that uses a visible, 670 nm, 5 milliwatt laser to yield an accuracy of 0.3 inches at a sample rate of 10,000Hz!  This class of  laser is similar to those used for common hand-held laser pointers and price scanners found in supermarket check-outs.  The laser unit also has an integrated internal heater so that outside temperature does not affect the accuracy of the measurements.

Initially, a Class IIIb laser was contemplated for use with this system, however, since DOT personnel  safety is of the utmost importance, a Class IIIa laser was chosen instead. This decision was arrived upon because according to the Code of Federal Regulations (CFR), "Class IIIb levels of laser radiation are considered to be an acute hazard to skin and eyes from direct radiation."  The CM-3000™ Class IIIa laser complies with CFR Title 21 part 1040.10 and 1040.11 and is register with the U.S Department of Health and Human Services Center for Devices and Radiological Health.  For more information on laser safety please consult the following websites:

Ultrasonic Sensor

To complement the "up" measurement supplied by the laser, the CM-3000™ uses a Smart Ultrasonic Sensor for making the "down" measurement. This sensor has an overall accuracy of ±0.25% of the distance measured and a sample rate of 100Hz in a 8º conical beam angle to retrieve the minimum distance. This sensor, in effect, "smoothes" out small imperfections in the roadway surface. Similar to the laser, the CM-3000™ ultrasonic sensor has an internal temperature probe to compensate for any changes in the outside temperature.

Mechanical Stabilization Device (MSD)

The FHWA requires that all clearances be recorded VERTICALLY.  This constraint resulted in the design and development of a damped-swivel system that automatically keeps the sensors vertical as the vehicle travels down the roadway.

    The MSD ensures a TRUE VERTICAL clearance measurement even on extreme super-elevations, crowned and deeply rutted roads.  This diagram is a representation of why the MSD is so important!  It can be seen that if the unit was rigidly connected to the vehicle the measured clearance is incorrect and larger than the true vertical clearance.  The CM-3000™'s MSD is allowing the unit to take a true plum (vertical) measurement every time regardless of the road topography.

CM3000 Mechanical Stabilization Device

CM-3000 Mechanical Stabilization

Global Positioning System (GPS)

The CM-3000™'s optional GPS tracking system uses Wide Area Augmentation System (WAAS) differential GPS coordinates.  This system provides an overall accuracy of better than 8.5 feet.  Coordinates are stored for each pass under a structure and can be stored with respect to the minimum clearance location or combined with multiple passes under a single structure to provide one set of coordinates per structure.