Electrical Considerations
The Three Channel Input/Output Unit is loop powered and operates at 17-28V DC with protocol voltage pulses of 5-9V.
Operating Principles
The Three Channel Input/Output Unit supervises one or more normally-open switches on each of the three inputs. It is set to return an analogue value of 4 in the event of an open or short-circuit fault and 16 during normal operation. The status of the inputs is reported by means of three input bits. The change-over contacts of each relay are operated by three command bits. If the model is ordered with a short-circuit isolator the Input/Output Unit will be unaffected by loop short-circuits on either loop input or output.
Mechanical Construction
The Input/Output Unit is supplied in an enclosure for surface mounting or as a PCB. The enclosure is moulded from self-extinguishing, glass-filled ABS. Ten 16mm/21mm and six 22mm/38mm dual diameter cable entry knockouts are provided. Ten LEDs, six red and four yellow, are fitted to the PCB. All LEDs except the isolator LED can be disabled to conserve loop current. For each channel, one red LED is illuminated to indicate that the relay is set; a second red LED is illuminated to indicate that the switch input is closed and a yellow LED is illuminated to indicate an open or short-circuit fault. A separate yellow LED is illuminated whenever the built-in isolator has sensed a short-circuit loop fault.
Dimensions and weight:
250 x 175 x 75mm 621g (in enclosure)
140 x 160 x 18mm 111g (PCB only)
Backward Compatibility
The unit will operate only with control equipment using Apollo XP95 or Discovery protocol. It may also be used to replace earlier Series 90 Three Channel Input/Output Units.
Product Information
The Three Channel Input/Output Unit provides three voltage-free, single pole, changeover relay outputs and three monitored switch inputs.
