General Information - Emerson Nelson CM-1 Manual

GENERAL INFORMATION

The Nelson CM-1 Circuit Monitor is a scanning microprocessor system which sequentially monitors and
displays each circuit number and the status of each circuit.
The CM-1 is environmentally hardened and requires no protected operative environment. It can be located in
a control room or out in a plant. The low voltage, optically isolated design allows the unit to be installed in
Division 2 Hazardous Locations.
The CM-1 monitoring system:
•
Monitors electrical characteristics of each heater circuit, including voltage, amperage,
& continuity.
•
Is totally passive.
•
Has built in filters to eliminate false alarms due to electrical noise.
•
Monitors self-regulating, constant voltage, & series types of heaters.
•
Independent of control scheme - will work with ambient or pipe sensed systems.
•
Can be retrofitted into existing systems.
The main components of the system include:
•
A microprocessor based scanner that interrogates all circuit sensor cards and compares the data to its
programmed parameters. The maximum number of circuits monitored is 24.
•
Sensor Card - the sensor card contains the circuitry for 4 heater circuits. Six cards are supplied in a 24
circuit system. The sensor card monitors the current and voltage to each circuit and is interrogated by
the scanner.
• Display - the display shows what circuit is being monitored (.5" readouts). The status of the heater
cable controller is displayed. The L.E.D. bar lights display continuity, current and voltage status of
each circuit.
•
Continuity Monitor Device (CMD) - The CMD is a passive component. Parallel type cables require
the attachment of a CMD at the end of each circuit. The microprocessor looks for the device's
presence every time a parallel circuit is scanned to verify continuity of both bus wires. The CMD
draws a low level capacitive current when connected.
www.nelsonheaters.com
GA-2129 Rev. 11
Sheet 4 of 22
Jul. 2018