Vishay VT 200, Technical Manual, Page: 40 / 84

Calibration
Electronic Calibration (E-CAL)
VT200/220 Technical Manual, Rev 1.00.01
40
Doc # TM-VT200/220-EN
4.2.1
Calculating Calibration Values
Consider the following example. A scale has maximum capacity 30/60kg,
e=0.010/0.020kg, with 4 load cells of rated capacity 50kg - 2mV each and dead load
1.940kg. The load cell data, as noted in the manufacturer data sheet, is shown in the
following table.
Load cell Output at 50kg Zero balance
L/C1 1.9793mV 0.0257mV
L/C2 1.9392mV 0.0276mV
L/C3 1.9577mV 0.0553mV
L/C4 1.9640mV -0.0022mV
To calculate the dead-load and span calibration values:
1. Calculate an average of the load cells’ rated output. In the example above, this
equals (1.9793+1.9392+1.9577+1.9640)/4 = 1.9600mV.
2. Calculate the combined output of the load cells when the scale is at maximum
capacity. In the example above, this equals 1.9600x60/4x50= 0.5880mV . This is
the
span calibration value
.
3. Calculate an average of the load cells’ zero balance. In the example above, this
equals [0.0257+0.0276+0.0553+(- 0.0022)]/4=0.0266mV.
4. Calculate the scale dead-load. In the example above, this equals
1.9600 mV*[1.940Kg/(4*50Kg)]=0.0190mV.
5. Calculate the overall dead-load by adding together the load cell zero balance and
the scale dead-load (calculated in step 4). In the example above, this equals
0.0266+0.0190= 0.0456mV . This is the
dead-load calibration value
.
4.2.2
Setting Zero Calibration (Dead-Load) Value
To set the zero calibration value electronically:
1. Enter the setup menus and use
TOTAL
( ) to scroll to the
CAL
menu. Press
PRINT
( ) to enter the menu.
2. Press
PRINT
( ) to enter the
E-CAL
menu.
3. Press
PRINT
( ) to select the
ZEro
option (zero calibration).
4. Enter the overall mV of the dead-load (see chapter 4.2.1 to learn how to calculate
it). Use
P.TARE
( ) to edit the current digit and
TARE
( ) to move to the next
digit.
5. Press
PRINT
( ) to record the zero calibration value. The display shows the
corresponding weight.