MTS DCPD Measurement System - Manual (Page 18)

DCPD Measurement System Introduction
The direct current potential drop (DCPD) crack measurement system is paired with an MTS closed-loop
servohydraulic controller. The closed-loop controller provides specimen loading, and data acquisition and
storage. A typical materials test applies a load or force on a specimen to grow the crack. In fatigue crack
growth tests, the load is a dynamic load simulating a material in a rotating or dynamic environment such
as an aircraft engine. In fracture toughness or creep tests the load is static or slowly varying, simulating a
material in other environments such as a pressure vessel.
Theoretically, the DC conditioners found in the MTS controller could supply the constant current and amplify
the electrical potential drop, but these conditioners do not have enough current or amplification for typical
DCPD specimens. Therefore, the DCPD Measurement System electronics provide the current and amplify
the resulting potential drop. Then the high level signal (amplified to a value between 0.1V and 10 V) is
brought into the controller or data logging device.
Component Identification (Rear View)
Description Label Item
Banana jacks to connect current leads. Current Out 1
Local adjustment, Remote connector, and selector switch. Current Set 2
The service port is used by MTS personnel for
troubleshooting. It provides a way to measure four things: Service Port 3
supply current, supply voltage, pulse command, and
direction command.
Selector switch to set the gain factor; either X1 or X10. Gain 4
Selector switch to set the low pass filter; either 50 Hz or
300 Hz. LPF 5
Cable connector to controller E-Stop. For non-494
controllers, please contact MTS Technical Support. E-Stop 6
18 | DCPD Measurement System
Introduction