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



Number Of Channels: 8 double-pole channels per unit
Number Of Channels Per System: Unlimited
Signals Switching: DPST reed relays
Contact Resistance: 0.2 Ω 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 Ω, 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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