• Typical Applicatons
• Factory Setting for Air Velocity and Temperature

The new thermal emulator, or "Thermulator," is a switching device that monitors both temperature and air velocity in a forced air cooling system. This dual output logic switch (DLS) has the unique capability of providing two separate, preset alarm logic outputs.

Completely self-contained, it monitors a rise in temperature or a decrease in air velocity. This solid state airflow switch is designed to provide an early warning "minor" alarm if the air velocity decrease or temperature increase has exceeded predetermined limits. A "major" alarm signal would be activated if this malfunction continued, requiring possible equipment shutdown or power removal. These alarms insure thermal protection for sophisticated electronic equipment. The Thermulator is factory set and ready for operation within customer circuitry.

The Thermulator is equipped with two distinct sensing levels, which may be used to increase the velocity of a cooling fan or blower to acceptable system limits. This adjustment should restore normal levels of air velocity and temperature. If the increase does not provide the desired correction, the Thermulator will provide the second or "major alarm" output, connected to provide either complete system shutdown or limit power to sensitive component areas.

Three different fan velocities can be controlled with the Thermulator. In this mode, an additional thermal device should be available to provide system shutdown. The Warren G-V Thermulator is power by a +5V.DC source, available in most modern systems. The input voltage required should be a low ripple regulated source with a maximum ±5% tolerance in voltage.

"Fail safe" logic level outputs, which require a minimum of 16mA load each, will provide a low logic level at the outputs under normal conditions. This configuration will switch to the high logic level in the event of an alarm condition. In this format a failure in the Thermulator, or its input voltage, will alarm both outputs. A low logic will indicate that the output transistor is "on" and sinking the current to ground (common zero volt).

Both outputs are open collector NPN transistors with emitters tied to common ground, allowing flexibility in the application of this device. External pull-up resistors will then be required at the output pins. The voltage on the outputs could be either +5V.DC or any voltage up to +30V.DC. Pull-up resistors are typically 1K ohms for 5V. TTL interfacing, and the maximum of 16mA loading applies for the other voltages.

The Thermulator will be factory calibrated at a fixed temperature setting, which has been standardized at 40°C. Warren G-V engineers can review other temperature setting selections from 25°C to 55°C upon request. The air velocity factory setting will be established at the selected temperature; differential between the two air velocities could be from 50 to 100 FPM. Calibration will be based on the "major alarm" air velocity at the selected air temperature. The "minor alarm" output will track the major alarm setting, at a pre-determined air velocity differential.

Both alarms will maintain their sequence as shown on the illustrated graph of air velocity setting versus air temperature. The graph plots an example of both a high and low setting. Other settings between the two levels can be factory calibrated.