Block Diagram And Operation Principle; Block Diagram; Operation Principle - KYOWA DPM-900 Series Instruction Manual

8-2 BLOCK DIAGRAM AND OPERATION PRINCIPLE

8-2-1 Block Diagram

8-2-2 Operation Principle

We explain it as follows depending on the above block diagram. Changes in physical quantities are
detected as changes in resistance of strain gages and converted in electric signals. As the result, the strain
gage bridges output minute AC volts. They are no more than hundreds of microvolt, normally. These
bridge output are amplified up to several volts through the carrier wave amplifier circuit that provides a
high AC gain.
Strain signals at up to this stage are superimposed over AC carrier signals so that they cannot be taken out
separately. So they are rectified then converted into DC by the circuit that detects the phase of resistive
signal components. They are further integrated through the low-pass filter, then output via the DC
amplifier.
The carrier filter and the low-pass filter have similar functions but they play quite different roles. The
former is indispensable in that it works to remove carrier signals, while the latter works to cutoff some of
signals and is not necessarily needed all time.
The features of the system can be summarized as follows.
Advantageous Features
• Signals are amplified in the AC form so that a highly sensitive strain amplifier is made possible.
• The temperature characteristic is superbly stable at the zero point. Excellent both in temperature
characteristic and long-term stability.
This is the most important feature of a carrier type dynamic strain amplifier.
• Carrier waves are transmitted via the input transformer so that they are hardly affected by surge noise.
From the construction mentioned above, a carrier type dynamic strain amplifier can well be an
isolated amplifier.
• Free from the effect of thermoelectric power.
• Less power consumption when compared to a DC amplifier.
41