Tecnetics Industries Tecweigh 20, Operation Manual

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7.03.2 Auto Span
AUTO SPAN is the next calibration step to perform. This procedure calibrates the scale using a
known weight, so the WP20 can accurately determine the material weight as it passes over the
weigh idler. With the conveyor running, press and hold the AUTO SPAN button for five
seconds. First, the message “HOLD TO SPAN” appears in the MODE window, then the message
“LOWER CAL WEIGHT”. At this time lower the calibration weight(s). The AUTO SPAN
procedure will begin when the calibration weight is sensed by the WP20. See Section 6.02.56 for
information on the Span Detect Parameter. The display in the MODE window should then
change to “AUTO SPAN WAIT”. A proper AUTO SPAN should take a minimum of two
minutes to complete. If, after lowering the cal weight(s), the “AUTO SPAN WAIT” message
does not appear, press and hold the AUTO SPAN button again for a few seconds. This action
will override the previous attempt and manually start the AUTO SPAN.
When the AUTO SPAN is complete, the message “RAISE CAL WEIGHT” will appear. Before
raising the cal weight(s) allow the RATE settle to a steady value. When the cal weight(s) are
then raised, the RATE display should return to ZERO and the calibration is complete. Totalizing
will not resume until the calibration weight is raised. An AUTO SPAN can be cancelled at any
time by pressing RESET.
Note 1: An AUTO ZERO can be performed without doing another AUTO SPAN, so as to re-
zero the belt due to zero drift. Zero drift can be caused by material build-up, variation of belt
tension, or changes in the environment surrounding the scale.
Note 2: If the AUTO SPAN had to be started manually, the Span Detect Parameter (Section
6.02.56) needs to be changed so the next AUTO SPAN request proceeds to completion. Change
this Parameter
after the calibration has been completed. To determine the new Span Detect
value, subtract the Zero Count (Section 6.02.58) from the Span Count (Section 6.02.59), and
calculate 70% (multiply by 0.7) of the difference and enter it as the new Span Detect value.
Now that the calibration is complete, the scale needs to be checked for accuracy. The following
calculated
value (or very close to it) is what you should see in the RATE window:
(?) (?) (total of one or both cal weights)
Cal Factor x Belt Speed x Cal Weight
Weigh Span = Rate (tons/hr.)
(refer to the Parameter Table (Sec. 11.02)
for known field data).
To verify the scale’s repeatability, lower the calibration weight(s) to see if the scale returns to the
RATE that was displayed after performing the AUTO SPAN. Repeating this procedure several
times will assure that the scale is performing properly.
7.03.2.1 Span Calibration for HY15 without calibration weight.
When using the standard model HY15 with 165 pound (75 KG) load cells, a calibration weight is
not required. The WP20 comes pre-programmed to automatically calibrate that size load cell.
IMPORTANT: When a calibration weight is not used, Parameter 5, “Cal Wt”, needs to be
changed from the default value of 120 to 0 (zero). This must be performed in the field.