Environmental response control apparatus and method
First Claim
1. In an environmental test system in which a device under test is contained in an environmental chamber, said environmental chamber including means responsive to a chamber control signal for setting an environmental condition within said chamber, and signal means in said chamber for providing a first signal indicative of the reaction of said device under test to said environmental condition and a second signal indicative of said condition, a control apparatus for generating said chamber control signal, said apparatus comprising:
- setpoint means for generating a test condition waveform;
a first control means connected to said setpoint means and to said chamber for generating a first operating point signal in response to said first signal and to said test condition signal;
limit means connected to said first control means and responsive to the magnitude of said first operating point signal for limiting said first operating point signal to a constant magnitude value when said magnitude exceeds a particular limit; and
a second control means connected to said limit means and to said chamber for generating said chamber control signal in response to said second signal and to said first operating point signal.
1 Assignment
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Accused Products
Abstract
A control apparatus for controlling the temperature of an environmental chamber within which a device is tested for thermal characteristics employs a pair of control elements connected in cascade. The first element produces a required air temperature in response to a desired temperature and to the temperature of the device; the second produces a temperature set point in response to the required and actual air temperatures. Possible stress on the device is avoided by limiting the range of required air temperature. Response is accelerated by a pass-through circuit, parallel to the first element, which responds to a change in the desired temperature by adding to the required air temperature of value proportional to the change.
52 Citations
11 Claims
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1. In an environmental test system in which a device under test is contained in an environmental chamber, said environmental chamber including means responsive to a chamber control signal for setting an environmental condition within said chamber, and signal means in said chamber for providing a first signal indicative of the reaction of said device under test to said environmental condition and a second signal indicative of said condition, a control apparatus for generating said chamber control signal, said apparatus comprising:
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setpoint means for generating a test condition waveform; a first control means connected to said setpoint means and to said chamber for generating a first operating point signal in response to said first signal and to said test condition signal; limit means connected to said first control means and responsive to the magnitude of said first operating point signal for limiting said first operating point signal to a constant magnitude value when said magnitude exceeds a particular limit; and a second control means connected to said limit means and to said chamber for generating said chamber control signal in response to said second signal and to said first operating point signal. - View Dependent Claims (2, 3)
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4. An environmental test system controller for controlling an environmental test chamber temperature in response to the temperature of a device under test in an environmental test chamber, said controller comprising:
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a setpoint generator; a primary controller connected to said setpoint generator and to said device for generating an operating point set signal; a pass-through circuit connected to said setpoint generator for providing a summing signal; summing means connected to said primary controller and to said pass-through circuit for combining said operating pointset signal and said summing signal to produce an operating point signal; a limiting circuit connected to said summing means for limiting said operating point signal to a range between a maximum temperature signal and a minimum temperature signal; and a secondary controller connected to said limiting circuit and to said environmental test chamber for generating a chamber temperature signal indicative of a temperature to be produced in said environmental test chamber, said secondary controller generating said chamber temperature signal in response to an operating point signal in said range and to the temperature in said environmental test chamber. - View Dependent Claims (5, 6, 7, 8, 9)
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10. In a system for subjecting a device under test to an environmental condition in an environmental chamber, a method for controlling said environmental condition, including the steps of:
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measuring the magnitude of a characteristic of said environmental condition to produce a signal PV2 ; measuring an effect produced by said environmental condition upon said device to produce a signal PV1 ; providing a setpoint signal SP1 to represent a desired effect to be produced upon said device by said environmental condition; producing a first operating point representation OP1 of said characteristic in response to SP1 and PV1 ; limiting the value of OP1 to a second setpoint value SP2 contained in a predetermined value range representing a range of values of said environmental characteristic within which said device is subjected to allowed environmental stress; producing a second operating point signal OP2 in response to a difference between SP2 and PV2, said second operating point signal representing a change in the value of said characteristic; and changing the magnitude value of said environmental characteristic in response to OP2. - View Dependent Claims (11)
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Specification