Showa 5683, Operation Manual

Page: 45 / 68

４−１１
2.00 gauge factor and the quarter-bridge configuration. The calibration values based on half- or
full-bridge configurations can thus be obtained by referring to the next table.
The relationship between the bridge supply voltage and bridge output voltage can be
represented by the following formula:
ｅ
= (K x
ε
x
Ｅ
x Bridge configuration)/4
Where: Ｋ ; gauge factor
ε
; Amount of strain (10
µ
ε )
Ｅ ; bridge voltage
Method True calibration value
One active one dummy Calibrated value on display
×１
Two active
Calibrated value on display ×１ /2
Two Gauge
Opposite arm, two active Calibrated value on display
×１
/2
Four Gauge Four active Calibrated value on display
×１
/4
Transducer Four active
Calibrated value on display ×１ /4
Table4-7
For details, refer to the remarks in the “Wheatstone Bridge Connections Table” on pages 4-3 –
4-4.
*Although transducers are generally based on the full-bridge configuration, their output is made
to match the quarter-bridge configuration.
(3) Where the distance from the bridge box to the amplifier unit is long
If the cable from the bridge box or a transducer to the amplifier unit is long, the bridge supply
will drop due to the conductor resistance of the cable. This causes errors between the bridge
output voltage and the CAL value. For obtaining the voltage drop rate, refer to “Bridge Voltage
Drop Rate” on page 4-6 or measure the voltage drop rate between terminals A and C on the
bridge box, using a voltmeter.
Example:
If the cable length is 100 m and the strain gauge resistance is 120
Ω
under an ambient
temperature of 20
°
C, the bridge supply voltage will be reduced by 5.8% between terminals A
and C, which can be obtained from the “Bridge Voltage Drop Rate Table” on page 4-6. The true
calibration value can thus be given by:
＝ ×
１
１−０．０５８
A
E
B C D
Voltmeter
AC Voltage
Measurement
Bridge box
Fig.4-8 Voltage measurement on bridge box
Such measurement and adjustment are not needed in Models 5683/5684
amplifiers thanks to cable length compensation.(Page 3-7).
Calibration
value on
display
True
calibration
value