Dakota Ultrasonics MAX-II Ultrasonic Bolt Tension Monitor

Price: $ 4,850.00
Ultrasonic Bolt Tension Monitor - Extensometer

The MAX II Ultrasonic Bolt Tension Monitor is designed for precision measurement of fasteners up to 100 ft / 30 m in length. It incorporates all of the great features of the original MiniMax unit, with improved features, hardware, speed, and range. The MAX II is designed for use in a wide range of industrial and lab applications.

The MAX-II Bolt Tension Monitor enables you to accurately monitor bolt tension ultrasonically measuring the elongation (change in length) of your bolts. It enables you to re-visit your bolts in certain intervals and monitor the quality of your bolt connections over time. The new "Auto Correlation" feature that helps you to optimize your transducer placement. Together with the large QVGA sunlight readable color display and the calibration function, it is very easy to use without the steep learning curves associated with other models.

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  • Measures: Elongation, Load, Stress, Strain and Time (nanoseconds).
  • Sunlight readable color QVGA display (320x240 pixels)
  • Measure Modes: Pulse-Echo, Echo- Echo, Echo-Echo-Verify (triple echo)
  • Auto Correlation - Transducer Placement
  • Custom auto calibration feature
  • 4GB internal & up to 64GB external SD memory
  • USB 1.1 connectivity
  • Analog, serial & alarm outputs
  • PC interface reporting software
  • Li-Ion pack & 6 AA emergency battery backup option
  • 2 year warranty
  • 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.
  • Gates: Three measurement gates, depending on measurement mode used, with adjustable start and threshold.
  • Alarm Limits: Adjustable Hi/LO tolerances with visual LED’s and audible beeper. Hardware alarm outputs (accesory cable required).
  • Field Calibration: Vector or Regression correction curve for increased accuracy using Load & Stress



UnitsEnglish (in), Metric (mm), or Time (µs)
Velocity0.0492 to .5510 in/µs (1250–13995 m/s)
Measurement ModesPulse-Echo (P-E), Echo-Echo (E-E), or Echo-Echo-Echo (E-EV)
Measurement Range1 to 999.999in (2540cm) in pulse-echo(P-E) measurement mode. Range will vary using multi-echo modes – dependent on material type and consistency.
DetectionZero Crossing
Resolution+/- 0.00001 in (0.0001 mm)
CalibrationAutomatic, Fixed, Single or Two-Point zero calibration options
QuantitiesTime – 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 MaterialsSelect types from a preset or custom list.


Weight4.5 lbs (2.04 kgs), with batteries
Size8.5W x 6.5H x 2.5D in (216 x 165 x 70mm)
Op Temperature14 to 140F (-10C to 60C)
KeyboardMembrane switch with 21 tactile keys
HousingExtruded aluminum body with nickel plated aluminum end caps (gasket sealed)
Display ViewsRF (full wave view), +/- Rectified (half wave view), Digits, or split screen combination (wave plus large digits)
EnvironmentalMeets IP65 requirements


SBDirect USB 1.1 PC connectivity
Power Connector12v @ 2amps, adapter 100-240 VAC, .7 Amps, 50-60 Hz.5 Pin Lemo (includes):RS232Output – RS232 PC serial interface.Alarm Outputs – Two independent alarm outputs triggered by the gates.Analog Out – Proportional outputs (amplitude or distance), 0-10 volts.
Transducer ConnectorsTwo LEMO 00 connectors


Log FormatsGrid (Alpha Numeric)
Capacity4 Gb internal & up to 64 Gb External SD slot
Screen CaptureTagged interface file (.tif) capture for quick documentation
Custom Setups64 user configurations

Power Source:

Lithium Ion Pack10.8v, 2 amp hrs, typical operation 18hrs.
Battery BackupEmergency battery backup. Six 1.5V alkaline, 1.2V AA Nicad cells, 1.2V AA NI-MH, or other other equivalent power source
Battery life (continuous use)Alkaline (12 hrs), Nicad (5hrs), and NI-MH (12hrs), with default settings.


DisplayBlanview sunlight readable QVGA TFT color display (320 x 240 pixels). Viewable area 4.54 x 3.40 in (115.2 x 86.4 mm), or 5.7 in (144.78 mm) diagonal. 16 color pallete, multiple color options and variable brightness
Screen Refresh Rate60Hz. Timing: Precision TCXO timing with single shot 100 MHz 8 bit ultra low power digitizer.
Pulser TypesSpike, Square Wave & Tone Burst.Pulser Voltage: 100 – 400v
Pulser Voltage100 – 400v
Pulse WidthSelectable step options Spike, Thin, Wide, HV Spike, HV Thin, HV Wide, TB .5MHz, TB 1MHz, TB 2MHz, TB 5MHz, TB 10 MHz. Spike 40 ns, Square Wave 80 to 400 ns, Tone Burst 50 ns to 1 microsecond.
Gain0 to 110dB with 0.2dB resolution. Manual and AGC control.
Damping50, 75, 100, 300, 600, & 1500 ohms.
Frequency BandBroadband 1.8 – 19 MHz (-3dB) filter.
Horizontal Linearity+/- 0.4% FSW
Vertical Linearity+/- 1% FSH
Amplifier Linearity+/- 1 dB
Amplitude Measurement0 to 100% FSH, with 1% resolution.
Delay0 – 999.999in (25,400mm) at steel velocity
Measurement GatesThree independent gates depending on measurement mode selected, with audible and visual alarms. Amplitude 5-95%, 1% steps.


TypesSingle element – 1 MHz to 10 MHz frequencies, and 1/8” to 1” diameters. Magnetic & Non Magnetic options available
Glue-OnAvailable for short bolts with minimal/short elongations to eliminate transducer placement errors.
ConnectorsMicrodot, Lemo 00, or BNC options depending on the transducer model selected.
Custom TransducersAvailable for special applications.


CertificationFactory calibration traceable to NIST & MIL-STD-45662A
Warranty2 year limited


Complete Kit

MAX-II supplied with 4 oz. Bottle of Couplant, RS232 Transfer Cable Lemo to DB9, USB converter cable to DB9, Carrying Case, 10’ Lemo to Microdot Transducer cable (N-110-0020), PC Utility Software, Operation Manual and Certification.

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Bolt Tension Monitor / Meter / Extensometer

  • The first cost effective ultrasonic solution available on the market


Dakota Ultrasonics MAX-II Ultrasonic Bolt Tension Monitor - Data Sheet
Dakota Ultrasonics MAX-II Ultrasonic Bolt Tension Monitor - Instruction Manual
Dakota Ultrasonics MAX-II Ultrasonic Bolt Tension Monitor - List

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