Definition of Ambient Temperature

"The temperature of the atmosphere, liquid, or other medium surrounding an object."
Source: The World Book Dictionary, © 1966 by Doubleday & Company, Inc.

Low Ambient Operating Temperatures

Almost all of our temperature controllers will function at ambient temperatures down to -20ºC (-4ºF).

Many designs will accept a -40ºC (-40ºF) operating ambient. Custom controllers can be built to operate down to -55ºC (-67ºF).

Operation at the low ambient is determined by the ICs used and their ability to have the correct gain and stable states. The output or load circuit may require increased drive to turn on. Any design that is specified to a low ambient operating temperature has been tested and shown to provide sufficient output drive at that temperature.

High Ambient Operating Temperatures

The high temperature is harder to define than the low, because the high ambient operating temperature depends upon the controller power dissipation and the heat sink dissipation.

For all our Pulse Width Modulated (PWM) controllers the following applies: The power dissipation of the controller is largely a function of the load current, and only slightly a function of the input voltage. Example: A unit running at 28v and 25 amps will dissipate the same power into the base as one which is 12v and 25 amps, however reducing the load current to 12.5 amps will reduce the power dissipation into the base by 1/2.

For an analog controller, the standard 1/4 power point analysis applies when determining power dissipation.

Specific Examples

TECC: The TE controllers are limited by the base plate (mounting bracket) temperature, because this is the heat sink for the bi-phase H-Bridge. Under full load the controller will be dissipating approximately 15 watts into the base plate, Therefore, if the controller is operated at elevated temperatures you need to provide additional heat sinking for the base plate. At laboratory temperatures (room temperature, about 20ºC or 70ºF) the controller will reach about 75ºC under full load. So if you provide an additional heat sink which results in, say. 70ºC in a 50ºC ambient, the controller will still function appropriately.

Model 5C6-353: This Laboratory Benchtop Temperature Controller with a 10 Ampere maximum output is designed to run in a laboratory environment. Maximum ambient operating temperature is 35ºC to 40ºC (95ºF to 104ºF).

Model 5C6-355: This Laboratory Benchtop Temperature Controller with a 15 Ampere maximum output is designed to run in a laboratory environment. Maximum ambient operating temperature is 30ºC (86ºF).

Model 5CX-140: The 5CX-140 series of controllers have a "derating curve" (see below) on the customer drawing that is defined by the temperature of the case.