9393PrincetonGlendaleRoad
Hamilton,Ohio45011
 
Revision1.2ROMIII“‐L”&“‐LIQ”Installation&OperationManualPageNo.6of15
 
Construction - The monitor is housed in a rectangular aluminum box enclosure with six ½ 
NPT threaded entries and a windowed cover held in place by six bolts. There are two circuit 
boards (Base board and Top board), the boards are encapsulated with only the wiring 
terminals and signal LEDs protruding from the encapsulation. The input terminals are 
separated from the intrinsically safe terminals by a metal partition. There on certain 
installations, there may be also a small encapsulated Model  #1910A 2-Wire Terminator.  
This “terminator”, 
is used to terminate the unused sensor input circuits.  It is typically installed 
vertically inside the ROM III enclosure at the lower left corner.  
circuit board the 1910 Terminator. The 1910 is mounted inside the ROM III enclosure and is 
used terminate the end of a string of output circuits. The Model  #1910A 2-Wire 
Terminator is typically installed vertically inside the ROM III enclosure at the lower left 
corner 
 
Ratings - The ROM III operating voltage is 9 – 30 Vdc, 1A.  The ROM III is rated for use in an 
ambient temperature range of -40°C to +70°C.   
 
Entity Parameters: TB2 
Uo (Voc ) = 11.8V, Io (Isc )   = 36.2mA, Po = 110mW, Co (Ca ) = 400nF, Lo (La ) = 3.8mH 
Vt = 11.8 V, It = 185 mA, Po = 0.546W, Co (Ca ) = 400nF, Lo (La ) = 3.8mH 
 
Entity Parameters: TB3 (only one type connection can be used at one time) 
Float Connections: Ui (VMAX) = 20V, Ii (IMAX) = 450mA, Pi = 1.0W, Ci = 0uF, Li = 0mH 
Therm Connections: Ui (VMAX) = 20V, Ii (IMAX) = 250mA, Pi = 1.0W, Ci = 0uF, Li = 0mH 
Optic Connections: Ui (VMAX) = 20V, Ii (IMAX) = 250mA, Pi = 1.0W, Ci = 0uF, Li = 0mH 
 
Entity Parameters: TB4  
AUX 1, 2, 3: Uo (Voc ) = 30 V, Io (Isc ) = 2.5mA, Po = 19 mW, Co (Ca ) = 400nF, Lo (La ) = 1.9H  
AUX 1, 2, 3: Vt = 30 V, It = 7.5 mA, Po = 0.546W, Ca = 400nF, La = 1.9H 
AUX OUT: VMAX = 20 V, IMAX = 50mA, Ci = 0nF, Li = 0mH 
 
Specific Conditions of Use: 
The enclosure is a potential electrostatic hazard. To prevent the risk of electrostatic sparking, 
the surface should only be cleaned with a damp cloth. 
 
 
4.  Top Only ROM III Onboard Monitor 
The ROM III monitor can be configured for top only (overfill) operation.  A terminal block 
connection is provided to disable the retain (bottom) circuitry.  Top only ROM III configuration 
will provide the advantages of 2 wire sensors and advanced diagnostics with the ability to 
install retain sensors at a later date.  This terminal block is located at the top of the unit, and 
is labeled TB4A.  A jumper wire is installed between the terminals to DISABLE the retain 
(bottom) circuitry.  It is pre-wired at the factory if the proper system is ordered.  DO NOT 
connect anything to the retain (bottom) sensor terminals.