Kistler-Morse KM L-Cell Bolt-On - Manual (Page 77)

Appendix D. System Calibration
D-3
Figure D-2. Manual Calibration Line
Weight Signal in Counts
Indicated
Weight
live load =
Zero_Cal
Scale Factor
Weight
Scale Factor
Counts
Note: Scale Factor Counts and Scale Factor Weight
establish the slope of the Manual calibration line.
Zero_Cal establishes the location of the line.
Slope =
Scale Factor Weight
Scale Factor Counts
See Figure D-2:
1. Refer to the signal processor manual to determine how to obtain the
A/D converter sensitivity, expressed in Counts/mV. Record this value.
2. Record the L-Cell sensitivity (S):
•
Carbon steel vessel —
35 mV/1000 psi (35 mV/0.7kg/mm
2 )
• Aluminum vessel —
80 mV/1000 psi (80 mV/0.7kg/mm
2 )
3. Refer to the Application Data Form for the vessel (if you cannot locate
the completed form, contact K-M for a copy). Record the maximum live
load and the stress.
4. Record the current live load in the vessel.
5. Calculate the Manual calibration values:
Scale Factor Weight = Maximum live load
Scale Factor Counts = S x Counts/mV x Stress
Zero_Cal = Current live load
6. Refer to the signal processor manual to input the calibration values.
Example: You are using L-Cells to monitor a 15’ diameter carbon steel, skirt-
supported vessel with 0.187” wall thickness. The vessel currently contains
50,000 lbs of material and can hold a maximum of 200,000 lbs. Following the
procedure:
1.
Counts/mV = 699.05 (from signal processor)
2. S = 35 mV/1000 psi (from L-Cell manual, for carbon steel vessel) = 0.035
mV/psi
3. From the Application Data Form, the maximum live load is 200,000 lbs.
The stress is:
200,000 lbs
3.14 x (15’ x 12”/ft) x 0.187”
=1892 psi
4. Current live load = 50,000 lbs
5. Calculate the values for the calibration:
Scale Factor Weight = Maximum live load = 200,000 lbs
Scale Factor Counts = S x Counts/mV x Stress
= .035 mV/psi x 699.05 Cnts/mV x 1892 psi
= 46,291 Counts
Zero_Cal = Current live load = 50,000 lbs
Manual Calibration
Note
K-M’s SVS 2000™
signal processor
performs a manual
calibration
automatically, with
Quick Config.