Truck Scales; Shift-Adjustment; Close Box; Final Calibration - Mettler Toledo Precision Junction Box AJB Serie Manual De Instalación

6.3 Truck Scales

Truck Scales usually use shims for height adjustment of load cell assemblies. Refer to the height adjustment procedure in the Installation
& Service Manual.

7 Shift-Adjustment

Shift adjustment is a process to equalize the output from all load cells in a system to minimize corner (shift) error. This step is relevant for:
• Multiple Junction Boxes connected via AUX
• Legal for Trade systems
• Scales where large loads can be applied eccentrically e.g. Floor Scales
• Scales with accuracy >2000d
Shift adjustment is typically not used on Tank Scales weighing liquids; also, skip when calibration by CalFree™ is sufficient. Perform shift
adjustment procedure now when applicable, see section 10 for details.

8 Close Box

• Tighten all cord grip nuts and caps. Close any unused cord grips with the plugs provided
• Place desiccant bag inside the Junction Box
• Ensure that the rubber gasket is clean and correctly positioned
• Replace the Junction Box cover and tighten equally all securing screws

9 Final Calibration

The most accurate and reliable way to calibrate a scale is to use test weights. With proper test weights (10% minimum) continue
calibrating the weighing system according to the instructions provided in the terminal manual. If using CalFree™ see below.
9.1

CalFree™

CalFree™ allows for calibration without test weights. Calibration Certificates are included with the load cells or refer to www.mt.com/
calfree. The accuracy of calibration by CalFree™ is limited especially on scales with attached pipes, and is not suitable for Legal for Trade
scales.
• Set all to SW to 80
• Continue with CalFree™ instructions provided with terminal

10 Optional Procedures

10.1 Range Setting

Set the Junction Box range according to load cell nominal resistance
• Load Cells < 1kΩ is the default, do nothing
• Load Cells ≥ 1kΩ cut all 1000R wires in all boxes
• Load Cells ≥ 2kΩ cut both the 1000R and 2000R wires/THD resistors in all boxes
10.2 Shift Adjustment
• Confirm that all SW switches are set to 80
• Apply test weight to 10 to 25% of scale capacity in the middle as shown on the left below.
Record the terminals displayed value as your reference value.
• Move the test weight to the first corner as shown on the right. Adjust the corresponding SW
until the display matches the reference value as close as possible. First turn up or down
the "x16" SW then the "x1" SW.
• Similarly move the load to the next corner and adjust. Carry on until the last corner has
been adjusted.
• Zero scale
• Establish a new reference value before the next cycle commences and repeat until shift values are within you tolerance.
• If after repeated test the corners do not match ensure that the scale is moving freely, the foundation is secure and any shims are correctly
placed. Record the switch settings for future reference.
• Go back to step 8.
4
Shift-Adjustment
30766399D Precision Junction Box