Transducer Inputs And Outputs - GE C30 Instruction Manual

CHAPTER 3: INSTALLATION
Figure 3-15: Current through contact inputs with auto-burnishing
50 to 70 mA
Regular contact inputs limit current to less than 3 mA to reduce station battery burden. In contrast, contact inputs with
auto-burnishing allow currents up to 50 to 70 mA at the first instance when the change of state was sensed. Then, within
25 to 50 ms, this current is slowly reduced to 3 mA as indicated. The 50 to 70 mA peak current burns any film on the
contacts, allowing for proper sensing of state changes. If the external device contact is bouncing, the auto-burnishing
starts when external device contact bouncing is over.
Another important difference between the auto-burnishing input module and the regular input modules is that only two
contact inputs have common ground, as opposed to four contact inputs sharing one common ground (see the Contact
Input and Output Module Wiring diagrams). This is beneficial when connecting contact inputs to separate voltage sources.
Consequently, the threshold voltage setting is also defined per group of two contact inputs.
The auto-burnish feature can be disabled or enabled using the DIP switches found on each daughter card. There is a DIP
switch for each contact, for a total of 16 inputs.
The auto-burnish circuitry has an internal fuse for safety purposes. During regular maintenance, check the auto-burnish
functionality using an oscilloscope.

3.3.6 Transducer inputs and outputs

Transducer input modules can receive input signals from external DCmA output transducers (DCmA In) or resistance
temperature detectors (RTDs). Hardware and software are provided to receive signals from these external transducers and
convert these signals into a digital format for use as required.
C30 CONTROLLER SYSTEM – INSTRUCTION MANUAL
current
3 mA
Figure 3-16: Auto-burnish DIP switches
842751A1.CDR
time
25 to 50 ms
842749A1.CDR
CONTACT INPUT 1 AUTO-BURNISH = OFF
CONTACT INPUT 2 AUTO-BURNISH = OFF
CONTACT INPUT 1 AUTO-BURNISH = ON
CONTACT INPUT 2 AUTO-BURNISH = OFF
CONTACT INPUT 1 AUTO-BURNISH = OFF
CONTACT INPUT 2 AUTO-BURNISH = ON
CONTACT INPUT 1 AUTO-BURNISH = ON
CONTACT INPUT 2 AUTO-BURNISH = ON
WIRING
3
3-19