Load cell selection and design
- Do select the right load cell for the application in terms of type and environmental compatibility.
- Do choose the right capacity.
- Do consider the required accuracy class.
- Do design-in adequate over/under load protection as well as protection from other mechanical damage (e.g. physical abuse, rodent problems).
- Don’t make the choice based only on price – cost of ownership is more important.
- Don’t use load cells above their rated capacity.
- Don’t over specify – look at overall system limitations on accuracy (e.g. mechanical pipe work, vibration etc.).
- Don’t ignore that hurricane or flood that comes once every 2 or 3 years.
- Don’t build in water / debris traps.
- Don’t assume “it” will never happen, and never use the load cell as a mechanical fuse.
- Don’t forget to provide adequate protection for the load cell cable, near the load cell if possible.
Proper care of your Load Cell
- Use stable power supply to prevent high voltage surges.
- Do not remove or tamper with the covers of your sensor.
- Monitor the temperature of the environment to ensure that it does not exceed the sensors operating temperature.
Installation and mounting
- Do store and handle load cells carefully prior to and during installation, and try to keep copies of the Certificate of Calibration in a safe place. Check load cells before fitting for correct model, capacity, thread combination, etc.
- Do use dummy load cells prior to installation.
- Do check that any threaded fittings screw smoothly into the load cell before final assembly.
- Do use care when tightening mounting bolts and restraints such as tie-bars.
- Do use lock nuts appropriate on threaded fittings, especially if vibration is present.
- Do use good quality connecting terminals / Junction Boxes / Solder joints.
- Don’t carry out electric welding near load cells.
- Don’t ever carry load cells by their cables!
- Don’t use excessive force when fitting / tightening mounting bolts or hardware, especially on low capacity cells.
- Don’t twist “S” cells when tightening threaded fittings.
- Don’t allow moisture to get at any interconnections.
- Don’t allow load cell to be the electrical link between ground and metal weighing structure.
- Use flat, parallel and clean mounting surfaces.
- In order to prevent zero distortion through dynamic overloading during installation, monitor your sensor (if possible) by connecting it to a display/ logger.
- If you’re bolting your sensor down, make sure you do not apply too much torque. Even a small bolt can easily exert high amount of force.
- Make sure that the load you apply on your Load Cell is applied in-line for a good measurement.
- Do regularly inspect load cells and weigh system especially after extreme weather conditions.
- Do check for corrosion damage to the load cell and mounting hardware. If practical, carry out cleaning and any remedial work (paint or other protective coating) before it is too late.
- Do give special care and attention to critical areas of the load cell such as metal bellows, seals etc. Those features are important in the operation and performance of the product.
- Don’t allow build-up of debris around load cell or mounts.
One of the most common failure modes of load cells is over loading. This is particularly an issue for low capacity sensors so they need to be handled with utmost care.
Here are some common tips.
- For Hydraulic or Pneumatic Pressure applications, slowly increase the load on the Load Cell to avoid a dynamic overload
- Avoid placing heavy fixtures on the Load Cell that may overload it. Again, very critical for low capacity models.
- If you think the Load Cell was overloaded, check the zero.
- Do not apply excessive torque or create a torque through the sensor when attaching the fixtures.
Connection & Cable
- Do not pull or yank on the Load Cell cable.
- Pinching and flexing the cable may cause damage, especially if it’s left in such a position for extended periods.
- The Load Cell spec sheet addresses the wiring code so refer to it if you are uncertain.
- In an environment with a high amount of moisture or humidity, create a drip loop on the cable to prevent any water from flowing into the sensor.
Finally, if failure occurs
- Do remove load cell with care and attach a label with comments relating to the problem or mode of failure.
- Do return a copy of the Certificate of Calibration with the load cell if available.
- Don’t cut cable at the gland to facilitate removal – please – we cannot test load cells without cables!
All MeasureX models have specifications sheets available on our web site (www.MeasureX.com.au), where complete specifications are detailed.