| 摘要 |
<p>1338999 Automatic temperature control systems COLTRON INDUSTRIES Inc 1 Dec 1969 [29 Nov 1968] 58533/69 Heading G3R In an automatic temperature control system, a temperature measuring signal is converted into a digital periodic pulse train and compared with a reference frequency to switch a triac or other device to control power to a heating means. In a simple arrangement an AND circuit receives sets of pulses and if two pulses from the train do not occur within the negative part cycle of the reference frequency output from the AND gate triggers a monostable multivibrator causing the triac to conduct for a fixed determined time. The periodic time of the pulses is low compared with the determined time which is itself short. A resistance sensor 11 is connected to a transistor Q2 which controls a constant current regulating transistor Q1 which charges a capacitor C18 at a regulated rate firing a unijunction transistor Q3 at a rate determined by the temperature sensed by resistor 11. Where this arrangement is mounted on a rotating body power is received by air cored coils L3 and the signal is transmitted through coils L1, L2. Coil L2 output may trigger a monostable multivibrator to produce a constant amplitude constant width pulse for each conduction of Q3 the resultant signal being applied over lines E, F to the circuit shown in Fig. 4. Coil L2 output may also be applied to an indicator and/or recorder calibrated in degrees of temperature. In Fig. 3 (not shown) an arrangement of similar configuration to Fig. 2 provides a reference frequency which is applied to a 4:1 frequency divider (35, 36) the output of which is applied over line 37 to a flip-flop chip A, Fig. 4, also to diode 43 which together with diode 44 forms a, AND gate. Flip-flop A is connected with a flip-flop chip B which is fed from lines E, F through an inverter 47 which furnishes a negative pulse train. If flip-flop B counts two pulses within the negative part of the wave on line 37, no output is given by the AND gate, but if a count of two occurs after line 37 swings positive, a positive output will be given from the gate. The AND output is inverted at 54 and operates a flip-flop circuit controlling a monostable pair of transistors 51, 52. For each positive output from the AND gate a positive pulse at terminal 9 of flip-flop 53 releases an oscillator including transistor 60 for a 0.1 second burst of 20hz pulses which are applied over lines M, N to the gate of a triac (not shown) passing current to a heater (also not shown). The reference frequency may be controlled and programmed by a computer and a number of systems may be connected to the computer in a time division mode of operation.</p> |
