MDD-1/T/420 Digital RS-485 output TS35

Device group: Addressable control units
Device type: MDD-1/T

MDD-1/T digital measuring control units are designed to connect one DEX/F, DEX/A, DG/F, DG.EN type threshold detector or one DEX/P, DG/P type measuring detector to the RS-485 industrial standard digital bus with MODBUS RTU protocol.

Features and functions performed

  • assigns three alarm levels to the measuring detector: A1, A2 and A3, set by the user to any value within the full measurement range;
  • assigns two alarm levels A1 and A2 to the threshold detector (according to the detector’s factory settings);
  • allows calculation of the PEL with TWA and average STEL for detectors measuring toxic gas concentrations;
  • allows to determine the type of displayed measurement units of the detector: [%] of the measuring range, [%LEL], [ppm] or [%V/V];
  • enables five modes of operation: “WITH MEMORY” – signals the occurrence of alarms after their disappearance, “UPHOLDING” – sustains active alarm states after the alarm source has disappeared, “A3 MODE” – turns off the power supply to the detector with catalytic sensor, which protects against overload, “WITHOUT MEMORY” – will automatically reset the input and output states on the front panel after the alarm states disappear, “SERVICE” – deactivates unit’s outputs for 1 hour;
  • visually indicates the signal value, the alarm and emergency states of the detector (LED display), the states of the control outputs A1, A2, A3 and the detector’s failure (LEDs);
  • built-in siren;
  • memorizes in a non-volatile internal memory the last 200 events with the assigned start and end times and source of the event;
  • enables very precise determination of alarm delay times and the invariability of these parameters over time thanks to microprocessor control;
  • two 12VDC alarm outputs (one for each A1 and A2 threshold) control additional acoustic and optical sirens;
  • relay outputs (galvanically separated, one for each A1, A2, A3 and failure) control fans, motors, contactors, information boards, or connect to building/plant automation;
  • isolated port in RS-485 standard (MODBUS RTU);
  • in the Digital Gas Detection System (with MDD-256/T type master controller) the connection unit is treated as a “detector”;
  • removable, screwless terminals, possibility of using wires with single or multi-stranded conductors (wires, without crimping sleeves) – quick installation, easy maintenance;
  • mounting on TS35 rail;
  • optional: isolated 4-20mA active analog output (model MDD-1/T/420) or 2-10V (model MDD-1/T/V10) provides control of inverters;
  • configuration of unit’s settings via the dedicated “DETnet View” configuration software, available at

Device model: MDD-1/T/420

Technical parameters

Maximum number of detectors
Alarm control outputs 12VDC
Contact control outputs
Emergency control output
Analogue 4-20mA output
Digital RS-485 output
Mounting on a TS35 rail
Supply voltage
106 x 90 x 65 mm
EAN Code
Net price
PLN649.00 N


Series Technical data Device information sheet Instruction manual Declaration of conformity

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