The supervisor was informed that the digital inputs on a remote unit for a 470m conveyor were not registering state changes correctly. Measurements found high voltages in the circuit, indicating noise interference from the long cable run. Adding a 10k ohm resistor in parallel stabilized the circuit by reducing the impedance and dividing the voltage, resolving the issue. Based on the results, the supervisor recommended purchasing 100 10k ohm 2W 5% resistors to address potential similar problems on other conveyors.

1. Assembly Supervision
Field solution. Supervisor: Sandro Nani
Report on problems encountered in the digital inputs of remote
inputs and outputs conveyor CV003, Antucoya mining,
Antofgasta Minerals.
On 28/12/2014, I was informed by the terrain staff after performing the switching of
various keys and sensors along the conveyor CV003, of 470m in length, the digital inputs
of the respective remote unit does not state exchanged.
So put me solve the issue by reviewing the following possibilities:
Voltage drop in the cables.
Electromagnetic induction.
Noise of R.F. .
On 01/05/15, with the multimeter Fluke175, I started to take
measurements in the circuit of the remote unit with Emerson entry card,
DeltaV system, as follows:
In this case
(Fig. 1)
measurements
indicate a
normal reading,
that is, the
voltage drop
between points
F and 2 and the
current card.
Figura 1
1

2. In this case (Figure
2), we find the open
switch, and between
its terminals one
89,7Vca voltage.
A voltage 76,8V
between points F
and 2. These figures
are very far from
normal.
The LED input
signal indicator
remains lit even
after the open
switch.
Figura 2
With these current and voltage values, it was evident that there was a problem
related to noise pickup due to the cable length.
Interference of EMI or RF were present in this case.
Even with the lack of an oscilloscope or other instrument of greater precision, it was
evident, by implication, that the problem was not a power failure but of voltage sum.
Even doubling the section of the cable moves, cable booking, no nemhuma
improvement.
All this led me to check the impedance of Emerson card.
As the impedance of the card is very high, around 63,5K Ohms, I started to test the
system with a resistor in order to download the full circuit impedance which can be seen in
the following figure:
2
0,015

3. Figura 3
As you can see, (fig.3) to put a resistor of 10K ohms in parallel with the F and 2
points, the circuit stabilizes. I called him Resistor Auxiliary.
It is evident that in this way it reduces external noise almost to zero, then respecting the
law of Ohm, We now have the expected voltage division at all points.
In the figure below we have the result of the current, now with the auxiliary resistor.
3

4. Figura 4
Thus, through the results obtained empirically in Figures 3 and 4, I come to the
conclusion that must be purchased the following resistor:
Ir1=U/R1
Ir1=120/10000
Ir1=0,012A
Pr1=V*Ir1
Pr1=120*0,012
Pr1=1,44W
R1= 10KΩ / 2W 5%
Recommend the purchase of 100 units for the same problem can occur in CV007 and
CV010 carrier.
Sandro B. de Nani
Sup.Mont Elétrica
4