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Originally Posted by kstl99
I have two questions. Our three sensors were powered with the black and white wires tied together. Can this destroy them?
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This should not have caused any damage. Since one output is switched to ground when the sensor is active, and the other output is switched to ground when the sensor is inactive, the combined wires would always have been grounded. Fortunately, grounding an NPN output has no lasting effects.
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After this error was found we bench tested two of them. We hooked one lead of a digital multimeter and the sensor's brown wire to +12 from the PDB. The sensor's blue wire was connected to the - of the PDB. The other lead of the meter was connected to the sensor's black wire. One showed +12 when the sensor saw or did not see the target although the indicator lights reacted, apparently bad. The second sensor we tested went from +12 to a reading of about 3 volts that drifted up to about 8 volts. Could the second one's strange reading be a result of using the meter as a load? We will test it on the sidecar tomorrow but I am curious about the reading.
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Did you have anything else connected to the sensor's output? The black and white wires do not supply current; they can only sink it. The voltage will read zero when the output is active. However, without a pullup resistor (which the Digital Sidecar pins provide), the signal will float to an indeterminate voltage when inactive.