Load cell basics – technical questions and answers part 1

Interface recently hosted a webinar on load cell fundamentals where our experts answered a number of questions from attendees. To share our knowledge and answer some frequently asked questions, we are offering a new series on our Interface IQ blog called Interface Technical Q&A. Following our presentation, we were asked several questions about the basics of load cells. We will answer them in two posts. Here is the first list.

Why does Interface use proprietary strain gauges?
Strain gauges are a key component of everyone load cell. Manufacturing our own strain gauges gives Interface full control over our design and production, ensuring we can meet our specifications with confidence in terms of quality, accuracy and reliability. Interface strain gauges are precisely matched to the load cell material to compensate for the influence of temperature on performance. We have different load cell materials and that means we use different strain gauges for each type.

Our strain gauges have a simple structure and we do not use any compensation resistors, making them a more reliable circuit. You don't have to go through resistance; therefore, the accuracy and precision measurement are more reliable and capable of faster thermal and higher performances.

What type of temperature testing do you perform on interface load cells?
Interface performs both hot and cold temperature compensation from 15˚ – 115˚F, including setup and verification cycle. Most other manufacturers of Load cells only offer hot side testing (60˚ – 160˚F). The slope of the curve is much flatter near room temperature and is identical at both ends of the slope. The result is a minimal deviation across the entire temperature range. We also offer custom calibrated ranges upon request. Read more about temperature compensation here.

Is temperature compensation achieved with dummy measuring devices?
The simple answer is no. Interface performs temperature compensation of the output by adjusting the strain gauge to zero material temperature compensation. This is achieved by using a wire in the circuit that counteracts resistance changes in the circuit.

Is there software for reading TEDS that can be used with interface load cells?
Interface offers instruments that can use the TEDS data as well as instruments that can write the TEDS data to the chip. Interface has software connected to the TEDS chip reader, so when programming a chip during load cell manufacturing in our factory, we can use software to perform this function. We also offer this software for commercial use.

Is it acceptable to regularly use a load cell beyond its stated capacity?
The short answer is no. You want to reserve the “excess capacity” for accidents. We recognize that people do this in practice, and the load cell will typically perform quite well above capacity. The problem is that you want to handle the answer “no” in a way that uses up your safety factor and leaves you with no additional margin for accidents. Additionally, using the load cell above capacity does not follow exactly the same calibration curve. If you e.g. For example, if you use a load cell with a capacity of 10k and a calibration of 10k and test at 12k, you may have higher errors. You can ask us to adjust the load cell to 12.000 lbs. to calibrate; However, you must note that this may reduce the safety factor, which is why we do not recommend this.

Do variable altitudes affect performance?
Interface is capable of handling various printing scenarios. Interface sends its products up when necessary to tolerate pressure changes without causing a zero shift. If you have applications where you have either high pressure requirements or pressure changes during testing, we certainly have solutions that can meet these requirements. Work with your application engineer to ensure you have the exact testing requirements specified when purchasing your next load cell.

Can cables have an influence on temperature errors?
If you add a cable to the load cell, e.g. For example, if you have a 10-foot cable and you want to add another 100-foot cable, this will increase the resistance. The lower the cable cross-section, the better. A 22-pin cable is better than a 28-pin cable. So use a thicker cable so that the resistance has less influence on the measurement.

Is the creep due to the material or the strain gauges?
Essentially all elements of the sensor and all mechanical components react to creep behavior. The goal is to match the creep behavior of the bridge to the creep behavior of the load cell material or bend. Yes, creep affects both, but you want the result to trend in the same direction so that you get minimal error or change in each value due to creep.

Are all load cells intrinsically safe?
These are intrinsically safe devices; however, if a hazardous environment or intrinsic safety requirements exist, please contact an application engineer to review the sensor use case and consider all aspects of your testing and deployment environment. The load cells typically operate in the 5-volt to 10-volt range and you need to consider all aspects of the location. For more information about our specialty products, see Load Cells for Harsh Environments.