doble TDR9000, User Manual, Page: 384 / 454

Pre-Insertion Resistor Timing
D-2 72A-1898 Rev. A 11/01
Monday
, November 26, 2001 1:09 pm
Pre-Insertion Resistor Timing
Resistor Switch timing is measured much the same as Main Contact
timing. When the measured voltage falls between the lower threshold
and the higher threshold, the channel is determined to be in the
resistance state.
Pre-Insertion Resistor Ohmic Value
The pre-insertion resistor measurement circuit employs the same voltage
source and source resistor as the contact timing circuits. The voltage
across the contacts is monitored by a voltage to frequency converter
whose output is optically coupled to a digital counting circuit. Knowing
the source voltage, source resistance and voltage across the pre-insertion
resistor contacts allows the actual pre-insertion resistance to be
calculated. The output of the digital counting circuit is updated every
800 µsec (1.25 kHz).
Motion Channels
Motion channels accept inputs from Doble motion transducers. The
transducers output two quadrature signals generated from optical sensors
which switch on and off based on a
picket fence of lines passing between
the sensors and a light source. Each transition is equal to a movement of
0.0125" (0.09° for rotary motion) imposed on the transducer. The
transitions are counted and sampled at 10 kHz. The direction of
movement is identified by which quadrature signals leads and which lags
at any moment in time. The distance curve is generated by providing a
running sum of the transitions vs. time, using the initial position as
zero .
The velocity curve is generated by taking the change in distance vs. time.
Auxiliary Contact Channels
The Auxiliary Contact channels measure and display the timing of three
different states: Open-Wet, Open-Dry, and Closed. An isolated wetting
voltage is provided for each channel that is not externally wetted to allow
for the differentiation of open vs. closed and to clean any oxide buildup
on the contacts. Both the open/close decision and the wet/dry decision
are made based on the voltage across the channel inputs. The states are
sampled at 10 kHz.