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Introduction
The CT398 is a programmable sensorless temperature controller designed to operate on DC power. When a high TCR
(Temperature Coefficient of Resistance) heater is used with the CT398, the heater element serves as the temperature sensor
which completely eliminates the need for a separate sensor during operation. An optical communication interface allows for
easy configuration on a computer; the included Windows software provides multiple methods of characterizing a heater and
configuring the Setpoint to any desired value.
The CT398 utilizes the same footprint as Minco’s original HeaterStat, the CT198; however, the CT398 is shorter, has a higher
current rating, and has full programmability: All settings can be programmed and changed by the user.
The CT398 utilizes on/off control by applying power to the heater element when the measured heater resistance, which
increases with temperature, is below the Setpoint. When power is applied to the heater, the resistance of the heater is
constantly being measured. When the measured element resistance is above the Setpoint, power is disconnected from the
heater except for during the Measurement Pulse. The Measurement Pulse is a momentary application of heater power for the
purpose of measuring the heater element resistance. See the Output Settings and FAQ sections for more information on the
Measurement Pulse and Pulse Heating.
Depending on the characteristics of the thermal system, the difference between the heater element temperature and the heat
sink may vary significantly. Since the CT398 directly measures the heater element and applies the control output accordingly,
care should be taken to ensure that the overall system is controlled to the desired operation using external validation.
The CT398 is ideal in situations where additional wires for a sensor are undesirable, or where precise temperature control is
unnecessary and simplicity is important.
Conventions
Different typestyles are used throughout this manual to make it easier to convey whether the text refers to a physical feature of
the CT398, or if it refers to a general term.
A word or phrase with first letter capitalization (such as Heater Output) refers to a feature on the CT398 such as a terminal
block connection or a feature such as Device Name.
Installation
All configurations are performed through the optical communication interface (AC221332, available separately) and the
Windows application. The CT398 must be powered, and its LED must be accessible to perform any configuration.
Mounting
The CT398 may be mounted via the mounting hole if desired and may be operated in any position
. A minimum of 1 inch (2.5
cm) airspace must be maintained around the sides and top of the CT398.
An exception is if a contacted surface is maintained
at or below the assumed ambient temperature.
Wiring
Only three wire connections are required: Power, Ground, and Heater. Each connection is explained in the following sections.
