Interface Data Sheet 101

Interface offers detailed specifications for all our products in a data sheet format. These comprehensive documents are much more than a summary of a load cell, instrumentation device, or accessory. The details in Interface’s data sheets provide essential mechanical and electrical information to help you select the right products for your specific test and measurement projects and programs.

Consider data sheets as a technical roadmap. Interface’s technical product data sheet includes a brief description of the product’s features and benefits, a reference image, performance details, and an outline drawing. The characteristics defined on a product data sheet are used to distinguish successful validation from a system failure.

TIP: Interface offers a downloadable data sheet for every standard product we sell. We also have an easy-to-reference online page for each product that highlights the individual model’s features and benefits, specifications, dimensions, diagrams, and details, such as characteristics, connectors, and wiring, when applicable.

The Framework of an Interface Data Sheet

At Interface, we synthesize specifications into four distinct categories to provide a holistic view of the sensor’s capabilities:

• Functional specifications focus on the sensor’s intended behavior and task performance. They outline what the system is designed to do, including expected use cases, application requirements, and the results of specific tasks.
• Technical specifications detail the product’s mechanical and material aspects. This includes physical dimensions, material composition, technical standards, and the capacities required for successful design and implementation.
• Performance specifications are the critical criteria for any metrology application. It defines the measurable requirements a product must meet, such as speed, accuracy, reliability, and efficiency, to ensure your testing goals are reached.
• Design specifications outline the visual appearance and physical constraints. They often serve as the primary reference for integration into larger assemblies, frequently pointing to outline drawings or STEP files.

Breaking Down the Performance Section

To understand a data sheet, we use the Interface 1200 LowProfile Series below as our primary example to illustrate what these technical terms mean in a real-world application.

The 1200 Series offers a robust measuring range from 300 lbf to 100K lbf (1.5 kN to 450 kN). When you look at the Model 1220 specifications in the series data sheet, you will see a list of percentage-based values. These are the rules of sensor accuracy.

To master a data sheet, you must adhere to precise metrological definitions assigned in mechanical and electrical specifications. Here are the top “must know” definitions, along with a reference to dive deeper into the subject.

• Nonlinearity: This specification is important because it affects measurement accuracy across the entire range, not just at full load. Lower nonlinearity values indicate a more accurate and higher-precision load cell. REF: Nonlinearity 101
• Hysteresis: The algebraic difference between the output at a given load when descending from maximum load versus ascending from minimum load. In precision sensors like the 1200 Series, this is kept extremely low, at +/-0.05%, to ensure data integrity throughout a full test cycle. REF: Hysteresis 101
• Static Error Band (SEB): This is the total maximum error of the load cell over its full capacity range, including the combined effects of nonlinearity, hysteresis, and repeatability. It represents the worst-case deviation between the actual applied load and the load cell output when the load is applied slowly under stable conditions. If your SEB is +/-0.04%, you know your total static error is tightly controlled within that window. REF: What is Static Error Band Output?
• Nonrepeatability: The maximum difference between output readings for repeated loadings under identical conditions. If you apply the exact same load under the exact same conditions five times, how much will the reading vary? The 1200 Series model 1220 boasts a nonrepeatability of +/-0.01%, ensuring that your data is consistent over time. REF: Demystifying Specifications Webinar Recap
• Creep: The change in signal occurring over time while under a constant load. This is a logarithmic effect that is also symmetric on load removal. REF: Creep 101
• Eccentric and Side Load Sensitivity: Eccentric load refers to forces parallel to but not concentric with the primary axis, creating moment loads. Side load refers to forces applied at 90 degrees to the primary axis. Sensitivity is reported as a percentage of the applied force. REF: Side Load Sensitivity 101

Understanding Environmental and Electrical Specs

A load cell is an electrical transducer, which means it is sensitive to its surroundings.

Temperature Effects
Every data sheet lists a compensated temperature range. For the 1200 Series, this typically ranges from 15°F to 115°F. Within this window, the internal strain gages are specifically designed to counteract thermal expansion or contraction. If you operate outside this window (but within the operating range of -65°F to 200°F), the sensor will still function, though you will need to account for thermal drift. This is the slight change in the zero balance or output due to temperature. REF: Understanding Load Cell Temperature Compensation

Rated Output (mV/V)
This is the sensor’s signal strength. For many 1200 Series models, this is standardized at 2.0 mV/V for aluminum flexures or 4.0 mV/V for alloy steel flexures. This standardization is a major benefit for engineers because it enables interchangeability. If you replace a 5,000 lbf cell with a 50,000 lbf cell of the same model, the instrumentation gain settings often do not need to be fundamentally changed, saving time in the lab. REF: Detailing Sensor Rated Output Millivolts Per Volt

Mechanical Integration

The data sheet also provides safe overload and deflection values. Safe Overload is usually listed as 150% capacity. This is your safety net. Exceeding this value can permanently deform the sensor’s internal structure (the flexure). Deflection at Rated Output tells you how much the sensor physically moves (compresses or stretches) at full load. For 1220, this is a tiny 0.002 inches. Low deflection is critical for high-frequency testing or applications requiring system stiffness.

Six Expert Tips to Master the Interface Data Sheet

#1 – Capacity Selection: The capacity is a critical balance between achieving a high-rated output (signal-to-noise ratio) and maintaining structural integrity. Selecting a capacity that is too low doesn’t just risk a permanent zero shift (immediate damage); it risks premature failure due to exceeding the sensor’s fatigue life.

#2 – The Fatigue Factor: Standard load cells are typically rated for a few hundred thousand cycles. If your application involves millions of cycles, you must use a fatigue-rated cell. Fatigue-rated load cells are designed for 100 million fully reversed cycles. For standard cells used in single-mode cycling, compression or tension only, staying within 30-50% of the capacity can mitigate risk.

#3 – The Whole-System View: Accuracy is a system-level attribute. Electrical noise from the environment and unshielded cables are common culprits of signal degradation. Furthermore, the quality of the excitation is critical. Any noise in the excitation voltage will be directly reflected in your measurement signal.

#4 – The Thermal Stabilization Rule: To ensure accuracy in varying environments, run the entire system, including all cabling and fixturing, up to the test temperature without applying force. This allows you to observe the thermal response and ensure mechanical joints have stabilized before taking data.

#5 – Calibration Alignment: Match your calibration to the test. If you only test in compression, a compression-only calibration is sufficient, but ensure it uses dead weight for the lowest traceable uncertainty.

#6 – Complete Systems: When purchasing sensors and instrumentation together, always opt for system-level calibration to ensure all components work harmoniously and to prevent performance errors before the equipment hits the lab floor.

Learn more from the experts in this webinar:

Mastering the technical nuances of a data sheet is the first step toward understanding the “why” behind the numbers. It helps ensure the integrity of measurement results and your investment in the tools needed to achieve your project’s objectives and ensure measurement success. Be sure to engage with our application engineers if you have any questions about the details in our data sheets.