Kval DL-2, Operation And Service Manual, Page: 64 / 80

DL-2 Sensors
KVAL DL-2 Series Operation/Service Manual
4-2
DL-2 Sensors
On the DL-2, sensors provide input to the PLC. The application in the machine is similar to a
micro-switch.
How Sensors Work
On the DL-2, sensors provide input to the PLC as part of the automation of the door cutting pro-
cess, including feed through, door clamping, and door location. The application in the machine is
similar to a micro-switch. It is important to keep the sensors cleaned and aligned to keep the door
process running smoothly. There are two classifications of sensors on the DL-2------Photo Elec-
tronic and Inductive Proximity Sensor.
The Photo Electronic Detector uses light as a trigger.
• Photo Eye Detectors contain both emitter and receiver. If an object is within the
Photo Eye’s sensing field light from the emitter is reflected from the object back to
the receiver. With
no object is in front of the Photo Eye a constant 24VDC is sent to
the PLC. If an object is sensed by the Photo Eye, 0VDC is sent to the PLC.
• As a result, any of the photo detectors output equals 0VDC when a door is sensed.
The Proximity Sensor detects metallic objects without touching them.
• An inductive proximity sensor consists of a coil and ferrite core arrangement, an
oscillator and detector circuit, and a solid-state output. The ferrite core and oscillator
create a field generating out the front of the sensor. When a metal object enters the
field, a loss in amplitude occurs. The detector circuit recognizes the loss of ampli-
tude and generates 0VDC to send to the PLC. When the metal object leaves the sens-
ing area, the sensor to returns to 24VDC and sends it to the PLC.
• As a result, if a metal object is sensed, the output of the sensor equals 0VDC.
Troubleshooting Sensors
If issues point to the sensors, use a DVM (Digital Volt Meter) at the PLC to check the voltages in
the “On” and “Off” states. Measure the voltages at the inputs at the PLC terminals. See the
machine drawing for detailed wiring connections.
• Photo Sensors often get dirty. Make sure they are clean. If they are not clean, debris
may block the signal or provide a false signal.
• Check output voltages of the sensors in the active mode. The voltage should effec-
tively equal 0 VDC
• Check the output voltages of the sensors in inactive mode.The voltage should effec-
tively equal 24 VDC
• The distance from an eye to the door should be in range. Typically the range should
be 3/4'' to 7/8'' from the top of all eyes to the door.