Interface Miniature Beam Load Cells Installation Help
The Interface MB Miniature Beam Load Cell (MB) is a high-performance, low-capacity miniature sensor engineered for precision and reliability in space-constrained environments. Designed to excel in both tension and compression, the MB series of Mini Load Cells is versatile for all industries, with uses ranging from small testing machines to OEM integration.
Interface Mini Beams, which are available in measurement capacities of 5 to 250 pounds force, are designed for controlled environment applications. In general, they can be used anywhere a readout instrument is used.
For step-by-step installation guidance, we have compiled a series of Interface technical resources, videos, manuals, design files, and product data sheets specifically for the MB product family, including the MB Miniature Beam Load Cell, MBI Overload Protected Miniature Beam Load Cell, and MBP Overload Protected Miniature Beam Load Cell.
Interface is dedicated to helping you achieve the highest possible accuracy with this high-precision mini load cell and integration, while also preserving the structural integrity of these compact measurement instruments.
The MB Anatomy and Function
The MB operates as a “beam type” load cell, utilizing a sophisticated internal structure to convert physical force into electrical data. The core of the load cell is the beam flexure, sometimes referred to as the spring element. Typically constructed from high-strength alloy steel, stainless steel, or aluminum, this element is engineered for controlled deformation.
A critical feature of the MB design is its ability to compensate for eccentric (off-center) loads. This ensures that even if the load is not perfectly aligned with the central axis, the sensor maintains high accuracy and reliability.
Interface temperature-compensated strain gages that are bonded to high-strain areas on the beam to measure the bending. The strain gages detect changes in electrical resistance. These are wired into a Wheatstone bridge circuit, converting mechanical strain into a stable millivolt-per-volt (mV/V) signal while minimizing noise and temperature fluctuations.
The MB features a fixed mounting end and a load-applying end. This configuration creates the bending moment across the beam required for precise measurement.
TIP: Watch Anatomy of a Beam Load Cell to learn more about the intricate design features of the beam-style sensor, inside and out.
Fundamental Installation Requirements
Rigid mounting is non-negotiable for achieving the ±0.03% accuracy rating. Any flex in the mounting surface will introduce measurement errors and hysteresis. Please exercise caution during handling and installation of these load cells.
Quick Specs Reminder of the MB Series
- Performance Accuracy: ±0.03% Full Scale (FS)
- Nominal Output: 3 mV/V
- Capacity Range: 5 to 250 lbf (0.02 kN to 1.11 kN)
- Low Profile Height: 99 in (25.1 mm)
- Overload Capacity: Applying a force exceeding 150% (1.5x) of the specific model’s rated capacity will result in irreparable mechanical damage to the spring element.
- Overload Protected: For users requiring built-in mechanical protection against over-capacity events, we recommend evaluating the Model MBI (Overload Protected) load cell, which shares similar form factors with integrated safety stops.
Primary Mounting Instructions
- The load cell must be mounted to a flat, rigid surface.
- Secure the mounting end using two 8-32 x 1.25-inch screws.
- Tighten mounting screws to exactly 24 in-lb (2.7 N-m). This specific torque value is required for optimal performance and repeatability.
Three MB Typical Installation & Mounting Methods
The following configurations are standardized for various industrial applications.
#1 – Typical Attachment
For standard force application, the load can be interfaced using:
- Threaded Rod: Utilize an 8-32 threaded rod secured with a standard 8-32 hex nut.
- Wire Cable: A 5/32-inch steel wire cable may be used, fastened with a 5/32-inch wire cable stop and secured via two set screws.
#2 – Preloaded Spring Overload Protection
In environments where dynamic forces may exceed the rated capacity, a preloaded spring assembly is recommended to safeguard the sensor. Assemble the components at the load hole in the following sequence:
- Finishing Washer: Use a #8 or 18/8 stainless steel finishing washer. This acts as a smooth guide to ensure the spring compresses cleanly without sliding off-center.
- Threaded Rod: Insert an 8-32 threaded rod through the washer into the load hole.
- Compression Spring: Slide the compression spring (0.75″ long, 0.174″ ID, 0.211″ OD) over the rod.
- Washer: Place a size #8 washer above the spring.
- Hex Nuts: Secure the rod with an 8-32 hex nut, and use a second hex nut to lock the spring-loaded assembly into place.
#3 – Platform Scale Mounting
When configuring a four-corner platform scale, an MB miniature beam load cell must be installed at all four corners on a flat, rigid base.
- Compression force is applied using 5/32-inch steel wire cables.
- The platform is secured by attaching a ball-with-shank and roller swage assembly to the lower end of the wire cable. This ensures a clean load path from the platform through the cable to the beam.
Technical Miniature Beam Configuration Considerations
The MB series is equipped with a 5-foot (1.5m) 4-conductor shielded integral cable (AWG 28). For precision measurements, engineers must account for this lead wire resistance in their instrumentation setup. The standard wiring configuration provides a “Compression Upscale” signal. This means the system will produce a positive-going (increasing) voltage signal when the load cell is under compression.
While some applications may suggest outdoor use, MB series load cells are strictly designed for controlled-environment applications. They should generally be used in locations where a readout instrument is operated under stable conditions. These units are NOT intended for submerged operation.
IMPORTANT! Applying a force greater than 150% of the rated capacity, which equates to 7.5 pounds force (lbf) on MB-5; 15 pounds on MB-10; 37.5 pounds on MB-25 and up, can result in irreversible damage.
Moisture-resistant coating is applied for capacities of the MB of 25 through 250 pounds to protect the load cells from high humidity conditions up to and including 95% Relative Humidity and periodic exposure to condensation. It is not a substitute for an environmental seal against weather or direct spray.
The miniature beam load cell, illustrated by the MB model with its notably low height, facilitates versatility and adaptability for installation across a wide range of applications. These compact sensors have become essential in aerospace advancements, industrial automation, consumer product design, research, medical testing, and general test and measurement, where spatial constraints are significant but accuracy remains imperative.
ADDITIONAL RESOURCES
Interface Mini™ Load Cell Selection Guide
Interface Mini Load Cells Growing in Product Use and Testing
The Marvels of Interface Mini Load Cells
Discovering Bending Beam Load Cell Use Cases
