ModWeigh MW93A - Page 8

EMC INDUSTRIAL GROUP LTD Features
MW93A_IM_ALL_SV6.09f_en 8/59
Weight Gain
Flow Regulators
SCREW FEEDER
VIBRATOR FEEDER
ROTARY VALVE
BELT FEEDER
DRUM FEEDER
TABLE FEEDER
PUMP
RESTRICTOR VALVE
Performance
One factor which determines the performance of a system is the capacity of the loadcell weighing sys-
tem used to weight the hopper. The following graph gives an indication of the useful operating range
that may be used. The Loadcell Capacity is the sum of the capacity of all loadcells, and should take into
account any lever system if one exists.
The performance is very dependent on the weighing system repeatability. It is desirable to aim for as
high a repeatability as possible. With care, it is possible to achieve weighing repeatability of 1 part in
10,000 to 1 part in 100,000.
The flowrate is measured by calculating the change in weight over a period of time. The error in this
measurement is limited by the length of time and loadcell accuracy. Calculate the ratio of flowrate (in
kg/h) to the loadcell capacity (in kg). Using this ratio, the following graph gives an idea of the flowrate
fluctuation for different measuring intervals (the flowrate response setting) and the loadcell incremental
accuracy.
FLOWRATE
[kg/h]
10,000
1,000
100
10
1
1
10
10,000
1,000
100
LOADCELL CAPACITY
[kg]
GOOD PERFORMANCE
POOR PERFORMANCE
ACCEPTABLE
BULK HOPPER
control valve
loadcells
WEIGH HOPPER
FLOW REGULATOR
Features
• interrupted flow
• simple installation
• ideal where bulk hopper & feeder al
ready
exist