The Dakota NDT MultiMax is a four-channel ultrasonic bolt tension monitor for critical bolted joints that need to be watched over time, not just checked once when they are tightened. Torque only estimates clamp load, because much of the applied torque is lost to friction in the threads and under the nut. The MultiMax instead measures how much each bolt actually stretches, by timing an ultrasonic pulse along its length, and converts that elongation into load, stress and percent strain.
Each compact module monitors up to four bolts and is run from a PC with Dakota's MultiUI software, either nearby or from a remote location. Modules can be connected together to monitor many more bolts from one screen, and readings can be logged automatically at intervals from six times a minute to once a month. Glue-on transducers can be bonded to the bolts for permanent installation, and built-in temperature monitoring and compensation keep the readings accurate as conditions change.
The MultiMax has a gasket-sealed, IP65-rated aluminum housing, follows ASTM E1685 for ultrasonic measurement of bolt elongation, and is made in the USA with a 2-year limited warranty. Transducers and cables are matched to your bolts and application, so contact us and we will help you configure a complete monitoring system.
- Four independent ultrasonic channels in one compact module – monitor four bolts at the same time
- Measures bolt stretch (elongation) directly and calculates load, stress and percent strain, avoiding the friction errors of torque-based methods
- Expandable: connect multiple MultiMax modules to monitor more bolts from a single PC
- Dakota MultiUI PC software for setup and live monitoring, on site or from a remote location
- Built-in command interface lets you control modules and channels remotely or integrate the MultiMax into your own monitoring software
- Automatic data logging from six readings per minute to once per month, stored on 4 GB of internal memory and exportable as CSV
- Auto Set configures detection, gating and display for each bolt automatically, with automatic zeroing
- Real-time temperature monitoring with automatic temperature compensation
- Works with single element transducers from 1 to 10 MHz, including glue-on transducers for permanent installation
- Rugged extruded aluminum housing with gasket-sealed end caps, rated IP65
- Powered from the PC's USB-C port or an AC adapter
- 2-year limited warranty; made in the USA
What the MultiMax measures: the change in length of a bolt or stud as it is loaded. A reading is taken on the bolt before it is tightened, and from then on the MultiMax tracks how much the bolt has stretched and reports it as:
- Elongation: change in length (in or mm)
- Load: clamping force (kip or MPa)
- Stress and percent strain in the bolt
Typical uses:
- Continuous monitoring of critical joints where loss of bolt load could cause leaks, damage or downtime
- Remote or hard-to-reach bolts where repeated manual checks are impractical
- Joint testing and R&D: tracking bolt load during tightening, relaxation, vibration and temperature cycling tests
- Short bolts with small elongations, using glue-on transducers to remove placement errors
Typical industries: energy, construction, automotive, aerospace and general manufacturing.
Each MultiMax channel connects to one ultrasonic transducer on the end of a bolt. The transducer, cable and connector are chosen to suit the bolt size, length and how long it will be monitored.
| Item | Details |
|---|---|
| Transducer type | Single element, 1 to 10 MHz, 1/8" to 1" diameter |
| Glue-on transducers | Bonded to the bolt for permanent installation and remote monitoring; they cannot shift between readings |
| Custom transducers | Available for special applications |
| Transducer cable options | Potted/integral, Microdot, Lemo 00 or BNC |
| Connections on the MultiMax | 4 x Lemo 00 (one per channel), Lemo 1 temperature sensor input and USB-C |
| Temperature sensor | Used for automatic temperature compensation |
Contact us with your bolt sizes, material and application and we will help you choose the right transducers and accessories.
Dakota MultiUI software: the MultiMax has no keypad or display of its own. It is set up and monitored from a Windows PC running MultiUI, which shows the waveform and a large live reading for each channel. Because the PC does the displaying, the MultiMax can be left at the joint while you watch the readings from somewhere else.
Automatic data logging: measurements can be saved automatically at intervals from six times a minute to once a month, so you can follow bolt load over hours, weeks or months. Data is stored on 4 GB of internal memory and archived automatically or manually in Dakota's format or as CSV for use in spreadsheets.
Expandable and open: several modules can be connected to monitor more channels from one PC. The built-in command interface lets you control each module and channel remotely, or build the MultiMax into your own monitoring or control software.
Accuracy tools: bolt materials can be chosen from a preset list or entered as custom values, and an optional correction curve based on known loads can be used for even higher accuracy.
Product images courtesy of Dakota NDT.
| Channels | 4 per module; multiple modules can be connected |
| Measurement mode | Pulse-echo |
| Measurement range | 1" to 50 ft (25.4 mm to 15.2 m), depending on material |
| Resolution | 0.00001" |
| Readings | Time (ns), elongation, load, stress and percent strain |
| Units | in or mm, µs, kip or MPa, °F or °C |
| Velocity range | 0.0492 to 0.5510 in/µs (1,250 to 13,995 m/s) |
| Calibration | Automatic or fixed; single or two-point zero; optional load correction curve |
| Bolt materials | Preset list or custom values |
| Transducers | Single element, 1 to 10 MHz; glue-on transducers available |
| Connectors | 4 x Lemo 00 (transducers), Lemo 1 (temperature sensor), USB-C |
| Temperature compensation | Automatic, with temperature sensor |
| Data logging | Automatic, from 6 per minute to once per month; 4 GB internal memory |
| Data export | Dakota format and CSV |
| Software | Dakota MultiUI for Windows PC (no keypad or display on the unit) |
| Power supply | USB from the PC or AC adapter |
| Housing | Extruded aluminum with gasket-sealed, nickel-plated aluminum end caps; IP65 |
| Operating temperature | 14 to 140°F (-10 to 60°C) |
| Dimensions | 3.0 x 6.5 x 1.5" (76 x 165 x 38 mm) |
| Weight | Approx. 16 oz (454 g) |
| Standard | ASTM E1685-20 |
| Certification | Factory calibration traceable to NIST |
| Warranty | 2-year limited |
| Country of origin | USA |
| Manufacturer part number | Dakota Z-226-0001 |
| Item | Description | Price | Lead Time | |
|---|---|---|---|---|
Dakota MultiMax - 4 Channel Bolt Tension Monitor - Transducers Sold Separately | $5,050.00 | 1 wk | ||
| Accessories | ||||
0.125", 5 Mhz, Top in, Microdot, Non-Magnetic Single Element Contact Transducer | $450.00 | In stock | ||
0.125", 5 Mhz, Side in, Microdot, Non-Magnetic Single Element Contact Transducer | $450.00 | In stock | ||
0.125", 10 MHz, Top-In, Microdot, Non-Magnetic Single Element Contact Transducer | $480.00 | In stock | ||
0.125", 10 Mhz, Side, Microdot, Non-Magnetic Single Element Contact Transducer | $480.00 | In stock | ||
T-5023-1855 | 0.250", 2.25 Mhz, Top, Microdot, Non-Magnetic Single Element Contact Transducer | $390.00 | In stock | |
T-4023-1855 | 0.250", 2.25 Mhz, Side, Microdot, Non-Magnetic Single Element Contact Transducer | $390.00 | In stock | |
T-5023-2855 | 0.250", 5 Mhz, Top, Microdot Non-Magnetic Single Element Contact Transducer | $390.00 | In stock | |
T-4023-2855 | 0.250", 5 Mhz, Side-in, Microdot Non-Magnetic Single Element Contact Transducer | $390.00 | In stock | |
T-5023-4855 | 0.250", 10 Mhz, Top-in, Microdot Non-Magnetic Single Element Contact Transducer | $415.00 | In stock | |
T-4023-4855 | 0.250", 10 Mhz, Side-in, Microdot Resolution Non-Magnetic Single Element Contact Transducer | $415.00 | In stock | |
T-5043-1855 | 0.5", 2.25 Mhz, Top-in, Microdot Non-Magnetic Single Element Contact Transducer | $390.00 | In stock | |
T-4043-1855 | 0.5", 2.25 Mhz, Side-in, Microdot Non-Magnetic Single Element Contact Transducer | $390.00 | In stock | |
T-5043-2855 | 0.5", 5 Mhz, Top-in, Microdot Non-Magnetic Single Element Contact Transducer | $390.00 | In stock | |
T-4043-2855 | 0.5", 5 Mhz, Side-in, Microdot Non-Magnetic Single Element Contact Transducer | $390.00 | In stock | |
T-700-2405 | 0.125", 5 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $800.00 | In stock | |
T-700-4405 | 0.125", 10 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $820.00 | In stock | |
T-702-1405 | 0.250", 2.25 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $820.00 | In stock | |
T-702-2405 | 0.250", 5 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $820.00 | In stock | |
T-702-4405 | 0.250", 10 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $840.00 | In stock | |
T-703-1405 | 0.375", 2.25 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $830.00 | In stock | |
T-703-2405 | 0.375", 5 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $830.00 | In stock | |
T-704-1405 | 0.5", 2.25 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $840.00 | In stock | |
0.5", 5 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $840.00 | In stock | ||
T-706-1405 | 0.75", 2.25 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $895.00 | In stock | |
0.75", 5 Mhz, Top-in, Microdot Magnetic Single Element Contact Transducer | $895.00 | In stock | ||
A-000-9001 | Glue On Single Contact Crystals, 12pcs, .125" x .125" 7.5MHz, For use on fasteners with limited elongation | $145.00 | In stock | |
A-000-9003 | Glue On Single Contact Crystals, 12pcs, .100" x .100" 7.5 MHz, For use on fasteners with limited elongation | $145.00 | 2-3 wks | |
LEMO 00 - Microdot Single Probe Transducer Cable, 4 foot length | $85.00 | In stock | ||
V-000-0001 | 4 oz of couplant for Flaw Detectors & Thickness Gauges | $20.00 | In stock | |
12 oz of couplant for Flaw Detectors & Thickness Gauges | $32.00 | In stock | ||
V-000-0004 | 1 Gallon of couplant for Flaw Detectors & Thickness Gauges | $190.00 | In stock | |
X-000-0011 | 3" Steel Calibration Bar | $405.00 | In stock | |
X-000-0010 | 3" & 6" Steel Calibration bars - Nickel-Plated Steel | $690.00 | In stock | |
X-000-0020 | Triple Path Glass Calibration Block - 3" x 2" x 1" supplied in foam fitted carrying case | $1,235.00 | 2-3 wks | |
A-156-8001 | Magnetic Temperature Sensor for Bolt Tension Meter | $570.00 | In stock | |
N-250-0001 | Power Adaptor (12 votls @ 2 Amps with 6ft cable) | $145.00 | In stock | |
N-120-6020 | 20’ Single Lemo 00 to Microdot (High Temp, High Wear Teflon) | $145.00 | 2-3 wks | |
LEMO 00 - Microdot Single Probe Transducer Cable, 6 foot length | $90.00 | In stock | ||
