Floor Scale Calibrations...

Seems simple at a glance but there are some nuances that a properly trained service technician should know before attempting adjustments

In the picture above you can see the electrical summing box open and our technician has placed 500 pounds of NIST certified test weights in the corner.  This is repeated on all 4 corners to ensure that the loadcell signal outputs are all properly balanced.  Once each corner matches exactly, then an overall span calibration can be performed.

Your typical warehouse floor scales have the following components:

• Steel or stainless steel weighing deck 
• • Which has 4 load sensors (load cell) bolted to the deck in each corner
  • Each load cell has an adjustable levelling foot
  • Within the deck each load cell is wired to a central Junction or summing box
• A single cable leaves the summing box and is connected to the digital weight display (also referred to as "Instrument", "Indicator", "Meter Head", "Read out" etc)

Is the scale mechanically isolated from any non-weighing components?

The scale deck should not be touching any nearby walls, conduits, pallets etc.  Many common issues we find are broken pieces of wood from pallets or general dirt and debris wedged under the scale...  Lift up your scale and clean it, then call us if you are still having issues.  If you don't want to clean it, call us and we can do it for you!

Is the scale deck level?

Poorly adjusted load cell levelling feet are common, forklifts accidentally running the forks under the scale will bend and damage the load sensor feet so that they cannot be properly adjusted and must be replaced.  

Are the load cell levelling feet properly adjusted to there is no rocking?

The deck should not teeter or rock around and should not have any bonking or clanging when walking around on the scale.  If so, this indicates that the feet need to be screwed in or out to ensure that all of the load sensors have equal forces applied when you load the scale.  The scale deck should have a bit of a floaty feeling when you stand on it as all of the feet typically have a "ball and cup" receptacle to allow a slight bit of mis-alignment on an uneven floor.

Is the weight displayed the same in every corner of the floor scale?

The above image shows the bolted end of the loadcell having come loose from the scale deck that it was supposed to be supporting.  This customer had called in saying the scale was not showing the same weight when pallets were on it.  Depending on how close or far from this corner the pallet was loaded on would cause the weight to increase or decrease.  The resolution was to lift the scale deck up, re-weld the loadcell mounting block to the scale deck, adjust the levelling foot and corner signals and then perform a span calibration.  Luckily this customer did not have to spend any money on components to get their device running again.

My scale keeps sliding all over the warehouse!?

One common issue we see with floor scales is the customer advising that their forklift operators will accidentally hit the side of the scale or just repeated sliding of the pallets onto and off of the deck gradually scoots the scale where it inevitably ends up hitting the wall or pallet rack nearby...  Which then causes the weights to be off causing expensive "Re-Weigh fees" from the freight carrier later or losses in invoicing if selling product based on the scale weight.

Typically you will see angle iron bolted to the ground around the scale in an attempt to keep this from happening but this does not fix the root cause...  In the image above you can see the plate bolted to the ground which captures the levelling foot.  By constraining all 4 levelling feet this way it avoids anything potentially touching the weighing surface causing accuracy issues later.

My scale weight is not stable, it keeps drifting up and down and counting up...  What Gives?

The most common cause of floor scale service calls are typically due to damaged cables, loose or poorly manufactured load cell connectors or terminal blocks and water intrusion for outdoor applications.  The connector in this cable was located on a pallet wrapper/scale combination.  When the pallet would shake the device as it was running it would cause the loose pins in this connector to fluctuate wildly.  The best course of action was to hardwire this section from the junction box to the weight display and the problem was resolved.  

In the image below the forklift operator knocked the scale off of the area it was on and the cable was smashed and cut by the fork.  The customer called that afternoon and we were onsite at 6am getting it going for them the next morning.

Not all floor scales are electrical! 

We work with Emery Winslow Hydrostatic floor scales and truck scales as well as your more common electrical based load cell devices.  These types of scales float on a cushion of hydraulic fluid and send a pressure signal to a totalizer mounted on the wall next to the digital instruments.  This offers a unique solution keeping any sensitive components away from heavy washdown areas minimizing downtime and costly component replacements over the lifetime of the device.

  We have all of the specialized tubing, fittings, pumps and spare parts to repair and calibrate these devices quickly and professionally. 

This scale has repeated heavy traffic with fork trucks which is hard on components over many years of multi-shift use.  Eventually the diaphragms wore down in the deck and required replacement.

Here is the diaphragm replacement on the load sensor:

Not all calibrations are created equal...

Make sure your existing scale provider is putting on at least 12.5% of the maximum scale capacity during your calibration inspections.  For a 5,000 pound capacity scale the minimum the scale should be checked with is 625 pounds for a legal for trade inspection.  We carry a standard 1000 pounds of NIST certified and traceable test weight on our service vehicles to ensure your scales are properly calibrated.