| | | Design considerations Minco will be pleased to provide assistance with any of the design steps below. Heater: A heater intended for use with a Heaterstat must have a temperature-sensitive element. All Thermal-Clear heaters meet this requirement, as do heaters with NiFe or NI foil. Installation: The Heaterstat is small enough to mount directly to printed circuit boards and will withstand both wave soldering and water wash. Secure it to the board through the mounting hole. If you intend to adjust the setpoint after installation you will need a hole in the board opposite the setpoint trimmer. The leadwire version does not require a circuit board. System accuracy: The Heaterstat, by its design, controls the temperature of the heater instead of the heat sink. The heater's element always runs hotter than the surface to which it is mounted. For best accuracy under changing ambient conditions, your design should attempt to either reduce this gradient or stabilize it to a predictable level. Some suggestions are: • Use the proper amount of heat. Try to size the heater to run at least 50% of the time in normal operation and at no more than 5 W/in2 (0.78 W/cm2). • Maximize contact between the heater and heat sink. • Stabilize the system. Maintain a fairly constant supply voltage and insulate the assembly from changes in ambient temperature. • Specify standard 1-second scan rate or faster. • Consider the CT325 miniature DC controller Setpoint calibration: A Heaterstat is factory calibrated to the nominal resistance of the heater at the setpoint temperature. Standard heaters, however, have a resistance tolerance of ±10%, or >25°C. For best results we recommend you recalibrate your Heaterstat after installation. Simply adjust the setpoint until temperature settles at the desired value as verified by a digital thermometer manufacturer such as the Minco Tl142. Where recalibration is impractical you can improve accuracy by ordering Heaterstats and heaters in matched sets. Minco can compensate for heater tolerance by calibrating the controller to the actual measured resistance of its mating heater rather than to the nominal resistance. The heater and controller will be marked with matching serial numbers. When ordering a Heaterstat for a matched set, specify model CT698 instead of CT198. | | Evaluation kits Test the concept and performance of Heaterstats before investing in a custom design. Each includes a controller and matching heater. You just supply electric power. Evaluation kit #4 Contains HI 5227 Thermal-Clear transparent heater and CT198-4. Order CT198-K4. Setpoint: Adjustable from -40 to 95°C. Voltage: 4.75 to 10 VDC. 5 VDC nominal. Watts: 1.7 W at 5 VDC and 50°C. Heater dimensions: 0.75" x 4" (19 x 102 mm). Scan rate: 10 seconds; Led indicator. Evaluation kit #2 Contains HK15228 polyimideThermofoil heater and CT198-2. Order CT198-K2. Setpoint: Adjustable from 0 to 120°C. Voltage: 7.5 to 38 VDC. 24 VDC nominal. Watts: 40 W at 24 VDC and 80°C. Heater dimensions: 2"X4"(51 X 102 mm). Scan rate: 1 second; LED indicator. Miniature Heaterstat controllers Minco can furnish SIP or DIP packages using remote digital setpoint adjustment. CT281 | | |