When load cells start to malfunction, they can prove to be a nuisance to the managers and operators in charge of them. They serve as the backbone for industrial scales, providing accurate measurements no matter the circumstances.
When they can’t provide that accuracy, then it can affect the business. That’s why it’s vital that you know how to identify potential damage, from physical breakage to the wrong type or range of voltage.
Fortunately, at Arlyn Scales, our experts have some answers to these problems. With our load cell troubleshooting guide, you will learn how to check load cells for these sorts of problems, and how to identify the potential issues.
Load Cell Troubleshooting Guide: How to Check Load Cells
Before checking your precision load cells, have your calibration information on hand. This helps you to identify the parameters and margins of error on input and output resistance, strain gauge resistance, and more.
We also recommend having a multimeter on hand to conduct certain tests so that you can identify the load cell’s current output with more accuracy.
Causes of Load Cell Damage
If load cells are dropped or mishandled, that can skew their results. The strain gauge is very sensitive and needs careful handling from operators. If a person accidentally drops the load cell, then it can cause damage to the load cell body and the interiors.
Moisture is one factor that can affect your load cell.
The water may cause the load cell to short out; this is a common problem in warehouses that have a high water level or outdoor industrial areas. It can also cause the interior parts to oxidize.
Sudden electrical surges, such as from lightning strikes, can also prove to be a problem. These sudden bursts of energy can permanently damage your load cells.
One strategy is to shield and ground your load cells. Also, you should implement surge protectors if connecting them to an external power source.
There are red flags when your load cell is not working properly. The first is inconsistency in the results that are displayed, also known as load cell drift.
If the cell is showing different results for the same item being weighed, then that means the load cell has a performance problem. Sometimes the display may show other errors.
In some cases, it may notify you about an overload when there is none, or it may not even register a load at all. Check your load cell between measurements: confirm that it goes to zero, and use a known item as a control group to confirm accuracy.
If zero balance vanishes, then that is also a red flag.
Load cells reset to zero after every measurement, as a means to maintain accuracy. If it doesn’t, then the results will prove to be inaccurate.
The zero balance needs to be within the margin of errors indicated on the calibration certificate. If this is not the case, then you potentially have a problem on your hand, especially if the changes are dramatic.
Checking Your Load Cells for Signs of Damage
Before conducting an assessment of any load cell, disconnect the load cell from any power sources. Your safety comes first before diagnosing any problems.
The first thing you should do is look at your load cell to find potential problems. A visual check may uncover physical damage that could be affecting the results — after all, the obvious signs often lead to the answer.
The load cell body should be intact and free of any obvious damage. The damage that happens to the exterior can affect the strain gauges on the inside, which in turn skew the measurements.
Aluminum is more prone to mechanical damage compared to stainless steel. Therefore, we typically recommend using a load cell body of stainless steel as opposed to aluminum.
Stainless steel is designed to be durable, waterproof, and corrosion-resistant with a high heat threshold. Even so, like other elements, stainless steel can be damaged, although it is more robust when compared to aluminum.
You can also determine if the load cell is bending unnaturally.
Since strain gauges are designed to measure resistance when an object is weighed, the cell itself should bend with the strain gauge. If that isn’t the case, then that could be another cause of issues.
The cell body’s flatness is very important for preventing load cell creep. You can make sure that the cell has not been distorted from shock overload or mishandling.
Cable connections are another potential concern.
Identify your cable connections as well; load cells have cables that connect to a power source, and use them to send signals. Damage to these cables can affect measuring the output, especially with sensitive equipment.
See if there are any cracks, distortions, ripping, or crimping on the load cell body or cables. In some cases, a short circuit may happen thanks to regular wear and tear.
Make sure that the mounting surfaces are consistent for the load cell, as disparities can skew the results. Finally, insufficient insulation can be another cause of inaccurate readings.
Electrical Leakage Checks
Resistance is one of the elements to check when testing your load cell for errors. This is because it’s related to potential electrical problems, such as causing the signals to become skewed or distorted.
You need a multimeter tool to run some of the tests that we recommend, as well as a voltage source.
It may simply be that you need to improve the energy source to fix any load cell issues. In addition, electrical surges can disrupt the input and output resistance, whether from lightning strikes or electrical issues.
You can tell if the input or output resistance is off by 3 Ω, or more from the specified values. Always test your strain gauges’ resistance; it is the heart and soul of precision and accuracy.
If your load cell has more than one strain gauge, then they need to be tested individually. Improper resistance could mean that your load cell is overloaded and the calibrations are off.
How electrically insulated is your load cell?
Most load cells operate by sending electrical signals, and insulation resistance contribute to accuracy. It should be more than 5 Giga Ω in an ideal situation. Test the resistance, and if it’s below a threshold of 2 Giga Ω, then there could be a problem.
You also want to determine input and output resistance; the cell’s specification sheet will tell you which defaults are necessary to meet. A multi-meter will help with checking these parameters, and your margin of error is typically 0.1 Ω. The load cell may be bad if it surpasses the .1 Ω margin.
When not checking the resistances, take a look at the load cell’s zero balance.
The load cell should reset to zero in between measurements and when it is not weighing an item. You can test this externally, using a multi-meter.
Use the load cell without weighing anything on it, and divide the resulting output voltage by the input voltage. This will give you the zero balance, and you can determine if it matches within the numbers on the calibration sheet.
Evaluate Your Shock Loads with Help from Arlyn Scales
With Arlyn Scales, you can determine the most efficient way to troubleshoot your load cells and prepare them for future operations. Our engineers revolutionized strain gauges so that they can handle weight more precisely while risking less damage.
Arlyn Scales wants to educate our customers about load cells and how to manage them. We also want to ensure that you have a high-quality scale with a load cell that is ready for the task, designed with stainless steel that will last for a long time.
Our team of metrology experts can advise you on updating and maintaining your load cells. To learn more about custom scales and the best load cells for them, reach out to our team today.