LIBRARY ı6ıul 0) - Cranfield University

Linear resistive transducer:
" Manufacturer:
" Type:
" Resistance:
Novotechnik
TLH-225
5kfl ± 20%
" Linearity: ± 0.07 %
" Voltage range
0-10 V
" Length: 234.5 mm
Measuring system:
" A/D converter board resolution:
" Measuring resolution:
4.9 mV
0.115 mm
In order to connect the digital inputs and outputs (I/Os) of the table controller
to the robot's, an interface box was built. The robot I/Os were designed such that on-
off switches could be connected to them. Since the table controller was designed to
work with 24 volt I/Os, a series of relays were mounted in a circuit board to provide
the interfacing between the robot I/Os and the table controller I/Os. The touch sensor
developed was also installed in this box. The circuits and external connections of the
interface box are described in Appendix G.
Figure 5.3 shows the full system in its final implementation.
5.7 Calibration
A careful calibration of the acquisition boards was performed by adjusting the
gain potentiometers of each channel to output 000h (hexadecimal) and FFFh for -10V
and +IOV volts input.
In the conditioning board, the voltage channel was calibrated to output signals
from OV to 10V, corresponding to inputs of OV to 100V. The current channel was
calibrated to provide unitary gain.
The D/A board was calibrated to output voltages from 0 to 5V. This was
amplified to provide 0 to 10V output, as required by the Robot Interface analogue
inputs.
The calibration for the output of the current probe was assumed to be correct,
according to the manufacturers data.
5.7.1 Moving table calibration
A calibration curve was obtained for the moving table by measuring its actual
movement and comparing it with the required one (see Figure 5.6). A Mitutoyo dial
gauge was used in the measurement trials.
5.7.2 Acquisition system calibration factors
The following calibration factors were used:
Voltage: 100
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