top of page

Dakota NDT MINI-MAX v2.0 Ultrasonic Bolt Tension Monitor

The MINI-MAX v2.0 Ultrasonic Bolt Tension Monitor from Dakota NDT allows for accurate measurement of the elongation produced by tightening a threaded fastener. 

The Dakota NDT Mini Max Bolt Tension Monitor measures the elongation very accurately in fasteners of virtually any material from 1/2 inch to 50 feet in length.


The bolt tension meter uses ultrasonics to measure elongation allowing the gauges to accurately measure time (nanoseconds), elongation, load, stress, and strain of the bolt.  The measurement is achieved by determining the change in the transit time of an ultrasonic shock wave along the length of the fastener as the fastener is tightened using a mechanical method. 

When nuts and bolts are fastened together under load the action of tightening the nut increases the force applied to the bolt causing elongation.

By using ultrasonics, bolt tension monitors are not affected by temperature, friction or resistance factors affecting the accuracy of standard torque measurement techniques - giving accuracy within 0.0001mm (0.00001 inch).

Dakota Mini Max Ultrasonic Bolt Tension Tester

Dakota Mini Max Specifications

Key Features:

  • Can measure bolts from 1/2″ up to 50 ft. (15.24 m).

  • Auto calibration for system zero.

  • Built in load calibration toolkit.

  • Wide range of material types and calibrations.

  • Selectable 200 volt square wave pulser (100, 150, 200 volts).

  • Variable transducer damping (50, 75, 100, 300, 600 & 1500 ohms), for use with 1-10 MHz transducers.

  • Large 110 dB gain range.

  • Variable digitizer for improved resolution and stability.

  • Temperature compensated.

  • Hi/Lo alarm limit used for for tolerances.

  • 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.

  • The Auto Set feature automatically optimizes detection and adjusts display.

Dakota NDT Bolt Tension Monitor
Technical Speificaton

Dakota Mini Max Technical Spec


Power Source


  • 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).

  • Environmental:  Meets IP65 requirements.

  • Line Power:
    USB to PC or power outlet.

  • Batteries:
    Alkaline 35 hrs, Nicad 10 hrs, NI-MH 35 hrs. Auto power off after 5 minutes idle. Battery status icon.




  • USB:
    Direct USB-C 1.1 PC connectivity. Windows & OSX interface software.

  • Line Power:
    USB-C to PC or AC adaptor.

  • Temperature Sensor:
    5 pin Lemo 1.

  • Transducer Connector:
    Lemo 00.

  • Log Format:
    Grid (Alpha Numeric).

  • Capacity:
    4GB internal SD memory.

  • Screen Capture:
    Tagged interface file (.tif) capture for quick documentation.

  • Custom Setups:
    64 user configurations.

  • Transducer Types:
    Single element – 1 MHz to 10 MHz frequencies, and 1/8” to 1” diameters.

  • Glue-On:
    Available for short bolts with minimal/short elongations to eliminate transducer placement errors.

  • Connectors:
    Microdot, Lemo 00, or BNC options depending on the transducer model selected.

  • Custom Trnasducers:
    Available for special applications.

  • Temperature Probe:
    Automatic temperature compensation.


  • Setups:
    64 custom user defined setups; factory setups can also be edited by the user.

  • Auto Set:
    Automates the detection, scope, and display setting process for each individual bolt.

  • Alarm Limits:
    Adjustable Hi/Low tolerances with visual LED’s and audible beeper.

  • Field Calibration:
    Vector or Regression correction curve for increased accuracy using Load & Stress.

Display Views

  • A-Scan:
    Rectified +/- (half wave view), or RF (full waveform view).

  • Large Digits:
    Digital display only.

  • Alarm Limits Bar:
    Hi & Lo alarm limits for displaying an acceptable tolerance range.

  • 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 invert).

  • Screen Refresh Rate:
    30 Hz.

  • Timing:
    Precision TCXO timing with single shot 100 MHz 8 bit ultra low power digitizer.

  • Pulser Type:
    Square Wave.

  • Pulser Voltage:
    Selectable 100, 150 and 200 volts.

  • Pulse Width:
    Selectable options Spike, Thin, and Wide. 80 to 400 ns.

  • Damping:
    50, 75, 100, 300, 600, & 1500 ohms.

  • Frequency Band:
    Broadband 1.8 – 19 MHz (-3dB) filter.

  • Horizontal Linearity:
    +/- 0.4% FSW.

  • Vertical Linearity:
    +/- 1% FSH.

  • Amplifier Linearity:
    +/- 1 dB.

  • Amplitude Measurement:
    0 to 100% FSH, with 1% resolution.

  • Delay:
    0 – 999.999 in (25,400 mm) at steel velocity.

  • Measurement Gate:
    One gate with audible and visual alarm. Amplitude 5-95%, 1% steps.


  • Units:
    English (in), Metric (mm), or Time (μs). Farenheit or Centigrade.

  • Velocity:
    0.0492 to .5510 in/μs (1250– 13995 m/s).

  • Measurement Modes:
    Pulse-Echo (P-E).

  • Measurement Range:
    1 to 999.999 in (2540 cm), dependent on material type and consistency.

  • Detection:
    Zero Crossing.

  • Resolution:
    +/- 0.00001 in (0.0001 mm).

  • Calibration:
    Automatic, Fixed, Single or Two-Point zero calibration options.

  • Quantities:

  • Time – Nanoseconds.

  • Elongation – Change in length (inches/millimeters).

  • Load – Force load applied (pounds KIP, or megapascals MPa).

  • Stress – Force for unit area stress applied (inches per inch or millimeters per millimeter).

  • Strain – Ratio of elongation to effective length.

  • Bolt Materials:
    Select types from a preset or custom list.

  • Repeatability Bar Graph:
    Bar graph indicates stability of measurement.



  • Factory calibration traceable to NIST & MIL-STD-45662A.

  • 2 year limited warranty.

Brochure Download - Dakota MiniMax

bottom of page