Determining The Correct Load Cell
To determine the correct load cell, there are several factors one needs to consider.
- Observe the environment your weighing system will be in and make note of the conditions. Is this a hostile environment with extreme temperatures, corrosive chemicals, excessive moisture, high vibration, or unequal loads?
- Will your weighing system be washed down with cleaning chemicals or at a high pressure?
- Load Cell Material
- Cable Composition
- Size
Using these conditions to determine the correct load cell and components will allow the weighing system to operate reliably.
Load Cell Material
A load cell is typically composed of tool steel, aluminum, or stainless steel. Tool steel is best for dry conditions because excessive moisture can rust the steel. This is the most common material for load cells. It is suitable for single and multiple load cell applications, and limits creep and hysteresis.
Aluminum is used for low capacity, single point load cells, and isn’t suited for moist or harsh conditions. Both 2023 Aluminum and 4340 Tool Steel are popular options because they return to their starting position after weighing.
Stainless Steel may be the more expensive option, but it performs the best in harsh conditions. It can withstand corrosive chemicals and excessive moisture. There are some pH levels that attack even the stainless steel, so you may want to check to see if you need to apply a coating to the stainless steel load cell.
Cable Composition
Now to think about the cables, strain gauges, resistors, wires, and seal options.
Most cables are made with a polyurethane jacket that protects against moisture and debris. If you need a cable to withstand extreme temperatures or corrosive chemicals, you will need a cable made with a Teflon jacket.
When it comes to sealing, there are several options. There’s a rubber boot, a glued cover, a potted strain gauge cavity, or a hermetically sealed load cell. The rubber boot, glued cover, or potted strain gauge cavity filled with material will keep the load cell protected from debris and moderate moisture. The hermetically sealed load cell will protect against chemical applications and excessive moisture. These load cells are typically made of stainless steel and has a welded barrier to cover the strain gauge cavity. The welded barrier further protects the load cell from harsh environmental conditions.
Size
The last factor to consider is the load cell size. Will this load cell be subjected to overloads, excess weight to one side, shock, or live and dead load miscalculations? You’ll want to be sure your load cell can deliver reliable results even under these conditions.
To determine the right load cell size, add the live load and dead load and divide by the total number of load cells. “This gives the weight that each load cell will be subjected to when the vessel is loaded to its maximum capacity.”
To account for overfilling, shock or unequal loads, add 25% to the number calculated. To account for excess weight on one side, have all load cells in the system account for the larger capacity. All load cells must have the same weighing capacity.
These are factors to consider when choosing the correct load cell for your application, but this is just part of the process. The installation is a critical component to ensure accurate weighing. You will want to seek out a professional to do the installation correctly. Give us a call to discuss your load cell application or request a quote!
