Dakota Ultrasonics Mini-Max Ultrasonic Bolt Tension Monitor

The MINI-MAX Ultrasonic Bolt Tension Monitor defines the state of the art in the measurement of the actual elongation produced by tightening a threaded fastener. MINI-MAX can measure the elongation very accurately in fasteners of virtually any material from 1/2 inch to 8 feet in length.


  • The first cost effective ultrasonic solution available on the market.
  • Effectively monitor your bolts during periodic shutdowns over the service life of the fastener.
  • Visually compare the unloaded to the loaded waveform.
  • Measurement quanities – Time (nanoseconds), Elongation, Load, Stress, and Percent Strain.
  • Display Options – RF, Rectified, Large Digits with Limits Bar.
  • Display Resolution – 1/8″ VGA 240 x 160 pixels.
  • Stores 8000 readings and waveforms in multiple groups.
  • Built-in Linear regression or vector for optimizing load measurements.
  • The Auto Set feature automatically optimizes detection and adjusts display.
  • Hi/Lo alarm tolerance limits work in conjunction with the data port and external pump shut-off device.


  • Size:
    Width (2.5in/63.5 mm)
    Height (6.5 in/165 mm)
    Depth (1.24 in/31.5 mm)
  • Weight:
    13.5 ounces (with batteries).
  • Keyboard:
    Membrane switch pad with
    twelve tactile keys.
  • Operating Temperature:
    14 to 140F (-10C to 60C)
  • Case:
    Extruded aluminum body with nickel-plated aluminum end caps (gasket sealed).
  • Data Output:
    Bi-directional RS232 serial port. Windows® PC interface software.
  • Display:
    1/8in VGA grayscale display (240 x 160 pixels). Viewable area 2.4 x 1.8in (62 x 45.7mm). EL backlit (on/off/auto).

Ultrasonic Specifications Measurement

  • Modes:
    Pulse-Echo (standard)
    Pulse-Echo w/Gate (fine adjust)
  • Pulser:
    Square wave pulser with adjustable pulse width (spike, thin, wide).
  • Receiver:
    Manual or Auto Set gain control with 40dB range.
  • Timing:
    10 bit 250 MHz digitizer.
  • Warranty:
    2 year limited

Power Source

  • Three 1.5V alkaline or
  • 1.2V NiCad AA cells.
  • Typically operates for 150 hours on alkaline and 100 hours on NiCad (charger not included.)
  • Auto power off if idle 5 min.
  • Battery status icon.


  • Range: From 1″ to 96″ (25.4mm to 244cm) bolts.
  • Time – Nanoseconds.
  • Elongation – Change in length (inches/millimeters).
  • Load – Force load applied (pounds kIP or kN Kilonewtons).
  • Stress – Force for unit area stress applied (pounds kPSI or megapascals MPa).
  • Strain % – percentage strain applied (inches per inch or millimeters per millimeter)
  • Resolution:
    +/- .00001 inches (0.0001 mm)
  • Velocity Range:
    .0492 to .3936 in/ms
    1250 to 9999 meters/sec
  • Fixed, Single, and Two point zero calibration options.
  • Select bolt material types from a preset or custom list.
  • Units:
    English & Metric / Fahrenheit & Centigrade


  • A-Scan – Rectified +/- (half wave view), or RF (full waveform view).
  • Large Digits – Display and toggle between nanoseconds, elongation, load, stress, and strain.
    Digit Height: 0.400 in (10mm).
  • Limits Bar(alarm limits) –
    Set Hi & Lo alarm limits for displaying an acceptable tolerance range.
  • Repeatability Bar Graph – Bar graph indicates stability of measurement.

Data Logger

Total of 8,000 readings, multiple bolt groups. Stores both waveform views, nanoseconds, elongation, load, stress, and strain for each reading.


16 megabit non-volatile ram.

Transducer Types

  • Single Element (1 to 10 MHz & 1/8″ to 1″diameters).
  • Locking quick disconnect
    “00” LEMO connectors.
  • Standard 10 foot cable.
  • Custom transducers and cable lengths available on request.
  • Temperature probe for automatic temperature compensation.


  • Setups:
    64 custom user defined setups. Factory setups can also be edited by the user.
  • Gate:
    Gate used to fine adjust where the detection point occurs.
  • Alarm Limits:
    Set hi and lo tolerances with audible beeper, viewable scan bar, and visual LEDs.
  • Auto Set:
    Locates the detection signal, optimizes the gain setting, and adjusts the overall display to show the waveform and detection point automatically.
  • Field Calibration:
    Vector & linear regression.
    Factory calibration traceable to national standards.