Trimming and Calibration
17
2. Move the weight cart directly over the next
paired cell section (2, 7 in Figure ) and record
the indicator reading.
Figure 6-7. Trimming Paired Sections 2:7, 3:6, and 4:5
.
Do the same for the last two paired sections
(cells 3, 6 and 4, 5)
.
3. Choose the lowest reading of the four as your
reference section, which will not be adjusted.
Using the
section
potentiometers, reload the
other three sections in turn and trim the
sections to match the
reading
of
the
reference section. Recheck section readings a
second time as the adjustment made may be
somewhat interactive.
4. As a final verification of the load cell
trimming, do a final corner check. Place a
1000 lb. weight on one corner of the platform
and record the raw-count reading on the
indicator. Move the weight to all the other
corners in turn and record those readings. The
readings should be within 1% of each other.
6.4 Calibration with Test Weights
The calibration procedure can only be done after all
trimming as described above has been completed. A
qualified scale technician with a test weight truck and
the expertise to access the scale indicator’s Setup or
Calibration mode must perform the calibration
procedure.
Figure 6-8. Calibration with Test Weights.
Equipment Required
Truck scales are routinely calibrated using 25% of the
capacity weight of the scale. Certified Class F test
weights equaling at least 12.5% of the scale’s capacity
will be required for calibrating a commercial
legal-for-trade truck scale. In addition, some type of
weight for a substitution test of an additional 12.5% of
the capacity will be required. This can be the
test-weight truck, bags of sand, or any convenient
items easy to load onto t he scal e. This total
calibration weight of 25% of scale capacity (12.5%
test weights, 12.5% substitution weight) is required by
weights and measures officials for commercial truck
scales in most states. Check with your local weights
and measures officials for the requirements in your
jurisdiction.
I n d u s t r i a l s c a l e s n o t u s e d f o r l e g a l - f o r- t r a d e
transactions do not require certified test weights.
We i g h t e q u a l t o 2 5 % o f s c a l e c a p a c i t y i s
recommended for calibrating such scales.
S e e
H a n d b o o k 4 4
f o r d e t a i l e d c a l i b r a t i o n
requirements and procedures.
1
4
3
2
8
5
6
7
1
4
3
2
8
5
6
7