Apparatus for controlling temperature

• US 3,924,102 A
• Filed: 05/22/1974
• Issued: 12/02/1975
• Est. Priority Date: 05/22/1974
• Status: Expired due to Term

• Current Assignee: Nicolaas W. Hanekom
• Original Assignee: Nicolaas W. Hanekom
• Inventors: Hanekom, Nicolaas W.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Bell, Fred E.
• Application Number:
  US05/472,122
• Time in Patent Office: 559 Days
• Field of Search: 219/494,497,499,501,504,505
• US Class Current: 219/497
• CPC Class Codes: G05D 23/2401 using a heating element as a sensing element

Abstract

Apparatus for controlling the temperature of a heating element comprising means to monitor the instantaneous magnitude of an electrical property of the element such as the impedance thereof. Conveniently this done by monitoring the instantaneous magnitude of the heating current flowing through the element. As the temperature of the element increases its impedance will increase and the instantaneous magnitude of the heating current will decrease. When the magnitude current of the heating current drops below a predetermined value, determined by the desired temperature the heating current is interrupted. Thereafter the heating current is periodically re-applied to the heating element for sampling purposes to maintain the heating element at the desired temperature.

Claims

1. Apparatus for controlling the temperature of an electrical heating element comprising means to connect the full voltage of an alternating electric power source to the heating element, means to derive a first voltage signal proportional to the current being drawn by the heating element, means to derive a second voltage signal proportional to the desired temperature of the heating element, means to compare the two voltage signals, means to disconnect the heating element from the power source when the magnitude of the first voltage signal is less than that of the second voltage signal, sampling means for then briefly connecting the full voltage of the power source to the heating element at periodic intervals for sampling purposes, and means to reconnect the full voltage of the power source to the heating element when the magnitude of the first voltage signal is greater than that of the second voltage signal.

2. Apparatus as claimed in claim 1 wherein the second voltage signal is a fraCtion of the voltage of the electric power source.