Kistler-Morse KM Microcell Bolt-On - Manual (Page 31)

CHAPTER 5. SYSTEM CALIBRATION
INTRODUCTION
This chapter describes general procedures for
calibrating the Microcell™ system. Before
calibrating, you must install a signal processor.
Refer to the signal processor manual for the
procedures to input calibration parameters.
There are two calibration methods:
A. Live Load Calibration — Set LO span and HI
span while moving material into or out of the
vessel. This is the preferred method.
B. Manual Calibration — Set scale factor counts,
scale factor weight, and zero calibration value
without moving material. This method is less
accurate than live load calibration.
A live load calibration requires you to move a
known quantity of material into or out of the
vessel while performing the procedure. The
quantity of material moved must be at least 25%
of the vessel’s total capacity to provide best
accuracy. Live load calibration is also based on
the material weight currently in the vessel.
Manual Calibration allows you to start using the
system as soon as Microcells™, junction boxes,
and signal processor are installed and wired, even
if you cannot move any (or enough) material now.
Manual Calibration values are based on system
parameters, including sensor sensitivity, vessel
support stress, and signal processor A/D converter
sensitivity. These values are known, can be
calculated, or can be obtained from the signal
processor. Manual Calibration is also based on
the material weight currently in the vessel.
Note that Manual Calibration does not take into
account the actual response to changes in weight.
Theoretically, a change in weight results in a
proportional change in digital counts. However,
the structure’s actual response to load and
interaction with piping, catwalks, roof, discharge
chutes, etc. prevents the system from achieving
theoretical values. Manual Calibration is a good
start, but to obtain the highest accuracy, perform a
live load calibration when scheduling permits you
to move material into or out of the vessel.
The following sections provide procedures for
performing live load and Manual Calibrations.
LIVE LOAD CALIBRATION
Live load calibration can be performed by
adding
or removing a known quantity of material
from the vessel. The quantity of material moved
must be at least 25% of the vessel’s total
capacity. The procedures for both live load
calibration methods follow.
ADDING A KNOWN QUANTITY
OF MATERIAL
See Figure 5-1.
1. Record the current live load.
2. Input LO Span: LO Span
= current live load.
3. Add known quantity of material to the vessel.
Ensure all material has stopped moving before
proceeding.
4. Input HI Span: HI Span = LO Span + Added
Weight.
Example
You are using Microcells™ to monitor a vessel. The vessel
contains 50,000 lb of material and can hold a maximum of
200,000 lb. You plan to add 60,000 lb of material (which is
greater than 25% of 200,000 lb).
Following the Live Load Calibration procedure:
1. Current live load = 50,000 lb
2. LO Span = current live load = 50,000 lb
3. Add 60,000 lb of material.
4. HI Span = LO Span + Added Weight
= 50,000 lb + 60,000 lb
= 110,000 lb
Figure 5-1. Live Load Calibration by Adding or Removing a Known Quantity of Material.
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