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PD138 MINUMUX II Temperature and Process Scanner

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The MINIMUX® II PD138 is a microprocessor-based, eight-channel analog input scanner/multiplexer and annunciator that provides low-cost automatic switching for multi-point display and alarm systems. It can automatically switch up to eight inputs to another device such as a digital panel meter, controller, or PLC. Signal switching is done via reed relays making the PD138 ideal for switching thermocouples, RTDs, control loops, and AC/DC signals. They feature rugged NEMA 4X/IP65 fronts and a wide operating temperature range. They can be programmed for many common ISA alarm sequences including first out indication and they provide alarm signaling through front panel LEDs and a build in 85 dB horn. Custom printed message labels can be included with your order at no additional charge.


  • 8 Inputs per Unit, Eliminates Need for 7 Displays
  • Unlimited Number of Units per System
  • Free Custom Message Labels
  • Thermocouples, RTDs, Process, AC & DC Inputs
  • Adjustable Dwell Time for Each Channel
  • Independent Alarm Input for Each Channel
  • First-Out Alarm Indication
  • Alarms Indicated by LEDs, Built-in Horn, and Relay
  • Built-in 85 dB Horn with Silence Pushbutton
  • Stop-On-Alarmed Channel (Field Select)
  • Non-Interruptible 4-20 mA Inputs
  • Sunlight Readable Indication
  • NEMA 4X/IP65 Front
  • Shallow Depth 1/8 DIN Enclosure
  • -40 to 65°C Operating Temperature Range

PD138 MINUMUX II Temperature and Process Scanner Data Sheet

PD138 MINUMUX II Temperature and Process Scanner Instruction Manual

General Specifications

  • Number Of Channels: 8 double-pole channels per unit
  • Number Of Channels Per System: Unlimited
  • Signals Switching: DPST reed relays
  • Contact Resistance: 0.2 O maximum
  • Maximum Input Voltage: 200 V (switched or common mode)
  • Maximum Current Switched: 0.5 A
  • Maximum Power Switched: 10 W
  • Dwell Time: Each channel adjustable from 0.6 to 30 seconds
  • Non-Volatile Memory: All programming values are stored in non-volatile memory for ten years if power is lost
  • Scan Method: Internal or manually controlled
  • Channel Indication: Green LED on front panel
  • Disabling Channels: Any channel may be disabled during setup
  • Scan Stop: The scan may be stopped by pressing and holding the STOP/GO button for more than 0.5 seconds. The scan may be resumed by pressing and releasing the STOP/GO button quickly (less than 0.5 seconds)
  • Alarm Input: Independent alarm input for each channel. Input Impedance; 25 K O, typical pull-up to 5 V
  • Alarm Sequence: Sequence A or Sequence F2A (first out)
  • Alarm Outputs: Alarm condition indicated by:
    1.Front panel red LED for each channel
    2.Relay, 1 SPDT (form C); rated 2 Amp @ 30 VDC or 2 Amp 2. @ 250 VAC resistive load; 1/14 HP @ 125 /250 VAC for inductive loads. For fail-safe operation, the relay is energized in the non-alarm state. In the case of a power failure, the relay will go to the alarm state, (NC contact is connected to common)
    3.Built-in Horn, 85 dB
    4.Stop-on-alarmed-channel (user select)
  • Alarm Acknowledge: Front panel ACK and rear connector terminals
  • External Switch Functions: The functions of the front panel buttons are available at screw terminals at the rear of the instrument
  • Message Labels: Free, custom printed, 2 lines per message at 14 characters per line. Factory or field printable. See manual for details
  • Connections: Removable screw terminal connectors provided:
  • Power + Relay: 22 to 12 AWG; Alarm Input, Analog Signal, External Switches, I/O: 30 to 16 AWG
  • Operating Temperature: -40°C to 65°C
  • Storage Temperature: -40°C to 85°C
  • Relative Humidity: 0 to 95% non-condensing
  • Power Options: 115 VAC, ± 10%, 50/60 Hz, 4 VA; 230 VAC, ± 10%, 50/60 Hz, 4 VA; 12-24 VDC (9-18 VAC, 50/60 Hz) 2 W
  • Led Test: All LEDs are tested on power-up
  • Enclosure: 1/8 DIN, high impact plastic, UL94V-0
  • Front Panel: NEMA 4X, panel gasket provided
  • Warranty: 3 years parts & labor



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Metex Corporation Limited has been providing superior products and services to the process control, chemical treatment, waste water, industrial and manufacturing industries for over 25 years. It is our goal to continually provide our customers with the best possible equipment, technology, and service.


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