McNab Model MDM Family Multi-Channel Monitor

product_MDM-ATC_Panel_A82-50_.jpg (49310 bytes)  


  • MDM-ATC Commercial
  • MDM-BTC Semi-Military
  • MDM-CTC Custom
  • MDM-RTC Repeater Multi-Channel Monitor


  • Up to 10 Channels
  • Temperature Timer Option
  • Automatic Alarm Update
  • Dump Valve Control
  • Recorder Outputs
  • Individual Modules



  • 10 channel capability.  
  • Salinity monitoring and optional temperature sensing/timed dumping.  
  • Front panel alarm level set point check.  
  • Subsequent alarm signaling to a remote location.  Suitable for unmanned engine rooms.

Feed & Condensate

  • Suitable for 1200 PSI plants.  
  • Automatic temperature compensation.  
  • Retrofit compatibility to existing 2 or 3 wire cell systems with minimum installation time.

Fresh Water Tank

  • Visual and audible alarm indicators.
  • 0-10 GPG, 0-100 PPM, 0-1000 TDS and other scales available.
  • Special Range Modules.

Reverse Osmosis

  • Failsafe dump valve control protects against contamination. 
  • MDM-ATC combined with McNab Model AP-I HC concentrated concentration

Cells and Insertion Valves

McNab cells and sensors are engineered to the most exacting specifications using only the finest quality materials.  They are available in both valve inserted and screw-in types with electrode configurations for virtually all applications.

Linear Safety Valves

These valves provide a safety interlock that requires the valve to be completely closed for cell removal and insertion.  Linear valves equipped with an operational assist mechanism are available.  This feature permits easy operation of the valve even against high pressure or vacuum.

Salinity readings are material-effected by the water temperature.  High water temperature causes the readings to appear higher than they truly are.  Early salinity equipment handled the problem by manual temperature compensation.  Our equipment has built-in temperature sensing arrangement, so as to achieve what is now called ATC (automatic temperature compensation).  This automation takes care of the problem.  Equipment is installed on piping systems or storage tanks for distillation, and feed and condensate systems.

Gate Valve Cells & Valves

The gate valve cell and valve are a traditional type of salinity sensor.  The MDM is compatible with the 3 major styles of these sensors.


For The Operator:
  • Designed from the ground up for commercial Marine service, not an adaptation from other services. 
  • Increased sensitivity, accuracy, and repeatability from rock-solid solid-state circuitry. 
  • Internal tamperproof, individual, calibrated setpoint control for each salinity module (meter independent). 
  • Individual, dedicated and labeled lights at the engraved cell directory provide simplified system status presentation. 
  • Available, built-in options include temperature-timer, recorder outputs, and audible alarms. 
  • Safe low voltage operation (OSHA). 
  • Simplified operating instructions on panel front. 
  • Color-coded meter. 
  • Long-lived front panel lights insure sustained performance of visual alarms. 
  • Compatible with rapid temperature response cells and safety valves. 
  • Front panel "Alarm Set Check" provides meter verification of setpoint levels.
For The Owner:
  • Automatic Over-range Alarm gives non-defeatable protection against costly operator mistakes.
  • Automatic Alarm Update and console outputs permit use in "one-man engine rooms ." 
  • Tamperproof setpoint controls. 
  • Remote console signaling of loss of power to panel. 
  • One family of designs suitable for both distillation plant, and feed and condensate systems (including 1200 PSI plants). 
  • Lower voltage solid state design extends cell life. 
  • Future expansion of system to ten channels is easily handled. 
  • Meets regulatory body requirements (MARAD, USCG, ABS, IEEE).
For The Shipyard:
  • Short-circuit proof cell drastically reduces system damage resulting from incorrect hook-ups (these problems represent 90% of installing difficulties). 
  • Generous internal clearances for cable bends and terminal connections speed installation. 
  • Standardized mechanical interface for either bulkhead or flush mounting. 
  • Panel compatible to retrofit into existing two or three wire cell systems. 
  • One-year warranty coverage from vessel acceptance.
For The Serviceman:
  • Individual modules for detection, indication, interconnection, temperature-timer, power, and switching functions.
  • No P.C. board misalignment is possible when replacing modules. 
  • P.C. boards environmentally protected. 
  • Parts readily available, no difficult-to-obtain MIL-SPEC parts. 
  • The standardized relay used throughout has a proven capability to handle the solenoid currents of large dump valves. 
  • Unambiguous power ON/OFF switch for safety. 
  • Electronic components rated with a 300% safety margin for power handling ability. 
  • Voltage status lights to aid trouble analysis.


Voltage: 115 V +/- 10%.  See CDS as appropriate.
220 VAC available
Frequency: 50 - 60 Hz +/- 10%
Phase: Single
Steady state current (max.) 2 - 3 amp
Peak surge current (max.) 15 amp
Cell Temperature: (min.) 40F (4.4C)
Cell Temperature: (max.) 225F (107.2C).  See CDS as appropriate.
Pressure Range: -14.7 to +150 psi (See McNab for higher values)
Panel Limits: 0F to 150F
Measurement accuracy: 3% of meter scale arc.
Alarm adjustment range: Not less than 3 GPG.  See CDS as appropriate.
Alarm level repeatability: 1/32" on meter scale.
Factory set alarm level: 0.25 grains/gallon, typical.
Automatic over range alarm: Not less than 10 grains/gallon or full range.
Automatic alarm update: Notice of subsequent alarm events.
Factory set dump limits: 0.25 grains/gallon (typical for public health)
Dump limit adjustment: With alarm level adjustment.
Low temperature dump level: 165F (73.9C) (typical for public health)
Low temperature dump time: 15 min. after temperature is raised to 168F (76.6C) 

383-2 East 29th Street | Buena Vista, VA | USA 24416-1293

540.261.1045 voice | 540.261.1268 fax |

Copyright 1999 - 2010  McNab, Inc. All Rights Reserved.  Last modified: 08.12.2010

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