Showa 5683, Operation Manual

Page: 40 / 68

４−６
Table4-4 Bridge voltage drop rate (%)
（
0.5mm
2
Wire
，
20
°
C
）
a. As shown in Fig. 4-1, pins A and C are provided for the bridge power supply, and pins B
and D are provided for the input to the amplifier unit. Pin E is the common terminal.
b. This is a bridge for measuring strain. Various methods are used for connecting strain
gauges. For details on these connecting methods, refer to “Examples of Strain Gauge
Bridge Configuration” on page 4-2. When using various types of transducers via the
bridge box, make connections as shown in Fig. 4-2.
c. If the cable from the bridge box or a transducer to the amplifier unit is long, the bridge
voltage will drop due to the conductor resistance of the cable as shown in Table 4-4.
Because the output voltage from the bridge deviates from the calibration (CAL) value due
to the bridge voltage drop, the calibration value must then be corrected. For information
on how to correct it, refer to “Correction of Calibrated (CAL) Value” on page 4-10. The
amplifier, however, has (standard) cable length correction that provides a proper bridge
voltage taking the conductor resistance of the cable into account. This enables precision
measurements without having to pay attention to the difference between the output
voltage and the calibration (CAL) value.
Distance between amplifier and bridge box (m)
Bridge Resistance
20m 50m 100m 200m
60
Ω
- 2.4 - 5.8 -11.0 -19.9
120
Ω
- 1.2 - 3.0 - 5.8 -11.0
350
Ω
- 0.4 - 1.1 - 2.1 - 4.1
500 Ω - 0.3 - 0.7 - 1.5 - 2.9
1000 Ω - 0.1 - 0.4 - 0.7 - 1.5
For information on how to correct the value, refer to “Correction of Calibrated (CAL) Value”
on page 4-10.
As the amplifier can supply the bridge voltage in which cable conductor resistance is
considered thanks to the cable length compensation function (standard), accurate
measurement can be made without regarding the error between output voltage and
calibration value.
d. Make connections by screwing and soldering when Models 5370 or 5373 are used. With
Models 5379 or 5380, make connections only by soldering.
e. If the lead wires from strain gauges to the bridge box are long, the gauge factor will
become apparently lower and the output linearity will deteriorate, even when the bridge
has been initially balanced. The lead wires, therefore, should be as short as possible (2 m
or less). The gauge factor of a strain gauge supplied with lead wires attached has been
calibrated together with the lead wires. Do not cut them or add other lead wires.