Precision Digital MINIMUX® II PD138 is a microprocessor-based, eight-channel analog input scanner/multiplexer and annunciator that provides low-cost automatic switching 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.
Precision Digital PD138 MINIMUX II Temperature and Process Scanner
- 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
General
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 the 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, a typical pull-up to 5 V
Alarm Sequence: Sequence A or Sequence F2A (first out)
Alarm Outputs: Alarm condition indicated by:
- Front panel red LED for each channel
- 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)
- Built-in Horn, 85 dB
- 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
Application
PD138 and PD765 to Scan Thermocouples
In the following application example, four oven thermocouples are scanned and channeled to a PD765 Temperature Meter where the PV is displayed and checked for low or high alarm conditions. All four ovens share the same low and high alarms, so the alarm inputs are joined together on the PD138.
The PD138 MINIMUX® II is programmed in the following manner to satisfy this application:
- Select alarm Sequence A
- Stop-on-alarm is off
- Program dwell times:
- Channel 1 for ten seconds
- Channel 2 for five seconds
- Channel 3 for fifteen seconds
- Channel 4 for five seconds
- Channels 5-8 are disabled
The PD765-6R2-00 Trident is programmed in the following manner to satisfy this level application:
- Select T/C
- Select °F
- Program alarm set and reset points:
The MINIMUX II scans each input and reflects the alarm state. The PD138 shown above is scanning input 1 (Green LED) allowing the Trident to display the current temperature of 250°. No alarm is present since the temperature is within limits. The MINIMUX® II only responds to new alarm conditions detected in the currently active channel. The PD138 also avoids false alarms by detecting alarm conditions only after dwelling on a channel for 2 seconds, or 0.05 seconds before it has been programmed to go onto the next channel if the dwell time had been programmed for less than 2 seconds. This gives the PD765 time to stabilize and accurately display the temperature and to check for alarm conditions.
The MINIMUX II switches to (scans) input 2 channeling it to the PD765-6R2-00 where a temperature of 345° is found to cause a high alarm condition. The PD138 is programmed for Sequence A, so the channel 2 LED alternately flashes yellow and green, the internal horn sounds, and the PD138’s alarm relay transfers causing an external horn to sound. After acknowledging the alarm the channel LED will glow a steady yellow (while selected), or steady red (when not selected) until reset.
The MINIMUX II switches to (scans) input 2 channeling it to the PD765-6R2-00 where a temperature of 345° is found to cause a high alarm condition. The PD138 is programmed for Sequence A, so the channel 2 LED alternately flashes yellow and green, the internal horn sounds, and the PD138’s alarm relay transfers causing an external horn to sound. After acknowledging the alarm the channel LED will glow a steady yellow (while selected), or steady red (when not selected) until reset.
The MINIMUX® II switches to (scans) input 3 channeling it to the PD765-6R2-00 where a temperature of 220° is found to cause a low alarm condition 2 seconds into the dwell time. Channel 3 LED alternately flashes yellow and green (shown yellow), the internal horn sounds and the PD138’s alarm relay transfers causing an external horn to sound.
Connections
Mounting Dimensions
Instruction Manual: PD138 Instruction Manual
Data Sheet: PD138 Data Sheet
Massage Labels: PD138 MINUMUX II Series Message Labels
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