| 摘要 |
<p>1429008 Automatic control systems SYBRON CORP 29 March 1973 [20 April 1972] 15243/73 Heading G3R [Also in Divisions H3-5] A summing amplifier system comprises a high gain inverting amplifier with a first impedance connected at one end to the input terminal for applying a first input signal, a second impedance connected at one end to the amplifier output terminal and at the other to circuit common, a third impedance connected at one end to a first point on the second impedance for supplying an input thereto, and a feedback impedance connected between the amplifier input terminal and a second point on the second impedance, the first point being electrically spaced at least as far from circuit common as is the second point. In a process controller inverting amplifier 21 is fed with an input signal via resistor 11, while the output is applied to an instrument 33 connected to a process control valve 34 in a pipe 35. The input signal is derived from a process variable transmitter 29 connected to a process sensing element 30, via comparison instrument 28 which generates the difference between the input from transmitter 29 and the desired valve, set by means of knob 31. Negative feedback is applied to amplifier 21 by means of a potentiometer network comprising resistors 24, 26 and potentiometer 25; in addition, an adjustable D.C. level shift is fed into tapping point 27 via resistor 17, from a control network comprising adjustable potentiometer 42, resistors 38, 41, and batteries 36, 37. Other impedances may replace the resistors; e.g. resistor 12 may be replaced by a capacitor to give integration.</p> |
