| 摘要 |
1,221,692. Automatic temperature control systems. ELECTRO-OPTICAL INDUSTRIES, Inc. May 15, 1968 [May 15, 1967], No.23079/68. Heading G3R. A temperature control system having a four arm electrical bridge including a temperature dependent resistance heater has a predetermined bias current passed through the bridge at balance to compensate for normal energy losses. The bridge 12 has in one arm a heater 14, preferably of high resistance, and other resistors, arranged to minimize the heat losses, the diagonal of the bridge being connected to a differential D. C. amplifier 40 controlling a transistor 50 which is cut off when the bridge is balanced. In this condition current is passed through the bridge by way of a resistor 60 the value of which is arranged so the heater 14 provides for normal losses in the system or body which is being heated. In another arrangement Fig.2 (not shown) the bridge is fed with A.C. and bridge current is controlled by a saturable reactor, a saturable transformer, or a phase controlled thyristor arrangement which is adjusted so that when the bridge is balanced a current of sufficient magnitude is passed to the bridge to make up for normal losses. In a further arrangement Fig. 3 (not shown) an A.C. source (136) may be connected to the bridge for detection purposes and a D.C. source (134) provides heating current. In Fig. 5 (not shown) the functions of these sources are reversed, and in Figs.4 and 6 (not shown) the A.C. and D.C. sources are connected in series appropriate detection and current control devices being utilized in each case. |
