Types
Amplifiers used in conjunction with transducers are available in 2 bridge excitation systems: constant voltage and constant current. These two systems have their respective features shown in the table below, to permit selection according to measurement purposes and applications.
All KYOWA strain gage transducers are calibrated at the factory using the constant voltage system.

※T series is provided with temperature measuring function

The reason why constant-current bridge excitation is used for with cable extended
If a 100 m long cable with cross-section 0.5 mm2 is used for connection between a KYOWA civil engineering transducer with bridge resistance of 350Ω and an amplifier of the constant-voltage bridge excitation system, sensitivity declines by approximately 2%. To avoid such inconvenience, it is recommended to use an amplifier of the constant-current bridge excitation system, which ensures measurement with less error.

Sensitivity change by cable extension and effect of constant-current bridge power supply
See Fig. 1 at the right and suppose that E is the voltage of the bridge excitation and E' is the voltage applied to the transducer in the constant voltage bridge system. Then,

E'＝E−2･I･r

where, "I・r" is the voltage decrease due to cable resistance and "2・I・r " is that due to the reciprocating cable resistance.

This means that extension cable resistance does not cause any output decrease. However, the input resistance, Rg, of the bridge affects the output. But a difference between the nominal bridge resistance of civil engineering transducer and its actual bridge resistance is extremely small, and thus it need not consider that the input resistance of the bridge affects the accuracy.