Showing papers on "Process variable published in 1970"

Floating-type electronic servo-motor process controller

Abstract: A floating-type electronic process controller including a differential amplifier which compares a voltage proportional to a process variable with a set point voltage to produce a deviation signal whose polarity and magnitude reflect the direction and extent of the departure of the process variable from the set point. The deviation signal is converted into on-off signals by applying it to a pair of comparator channels to which are also applied a triangular reference voltage having a constant frequency. When the deviation signal reflects a process variable which is below the set point, one channel is activated to yield square-wave pulses whose rate corresponds to the frequency of the reference voltage and whose pulse duration is proportional to the magnitude of the deviation signal, but when the deviation signal reflects a process variable which is above the set point, the other channel is activated to provide similar square-wave pulses. The square-wave pulses serve to trigger the triac control circuit of a reversible motor operatively coupled to a final control element, the pulses from one channel causing the motor to turn in one direction and the pulses from the other channel causing the motor to turn in the other direction, the duty cycle of the motor being determined by the duration of the pulses.

Industrial process control system for operations with long time constants

Abstract: A system for providing continuous and proportional control of a process variable includes a sensor furnishing an output signal having an analog value proportional to the process variable An analog controller includes a shaping circuit comparing that analog value with a reference to develop an error signal, and an integrator and two differentiators in series The time constant of the integrator is chosen to filter out fast, unwanted fluctuations in the process variable and the time constants of the differentiators to approximate those involved in the process work function The outputs of these elements of the analog controller are summed and supplied as a control signal to an actuator control circuit which varies the power supplied to an actuator so as to proportionally control a control parameter of the process In turn, changes in the control parameter bring the process variable back to its desired value An embodiment of the analog controller uses tantalum capacitors and high impedance operational amplifiers Embodiments of the actuator control circuits for use with AC synchronous stepping motors and DC motors include an integrator which eliminates any dead band in the actuator''s response to the control signal

Proportioning control unit

Abstract: A control device for producing a first control variable or parameter substantially proportional to the duty cycle or ratio of ''''on'''' to ''''off'''' times of a second variable by heating a block of metal or other thermally conducting material during the ''''on'''' time of the second variable and utilizing the resultant block temperature or some other proportional variable as a control variable. In the preferred embodiment of this invention, the block temperature is used to establish the temperature and hence pressure of a closed body of fluid which pressure may be connected for use as a control variable. Several specific temperature regulation systems using such a control device in a refrigeration system are also enclosed.

Process control circuitry

Abstract: A control circuit utilizes a bridge arrangement responsive to variable resistance in one arm thereof that varies as a harmonic progression to control an external device such as a relay. An opposite arm of the bridge serves as a linear set point control for the external device that controls a process variable.

Improvements in or relating to electrical indicating and monitoring apparatus

Abstract: 1,209,402. Automatic control. HONEYWELL Inc. March 12, 1968, No. 12023/68. Heading G3R. Anelectrical indicator is associated with switching means and differential circuits to indicate (a) the value of a controlled variable (b) a pre-set reference value and (c) when a second reference valve is adjusted to be equal to a first. In Fig. 1, a voltage dependent on the magnitude of a process variable is applied at 12 and compared by a differential amplifier 14 with a voltage from a potentiometer 36 set to correspond with a desired value of the variable. Any difference, representing an error, is effective, through a control amplifier 16 and a controller 18, to restore the variable to its desired value automatically. If the process variable deviates beyond upper and lower limits determined by the settings of potentiometers 44, 55, differential transistor or valve amplifiers 46, 60 cause relay operation of alarms such as 53. Additional relay contacts (not shown) controlling the transistor amplifiers ensure positive operation of the relays. A meter 20 has a scale which is adjusted relative to a fixed index by potentiometer 36 so as to indicate the desired value. The meter pointer is moved relative to the fixed index by the output of amplifier 14 to indicate the deviation. The indication of the pointer relative to the scale thus indicates the magnitude of the process variable. Operation of switches 24, 26 to their other position permits manual control of the process variable by a potentiometer 31 operating through amplifier 16. A condenser 28, charged during automatic control, and a condenser 22, charged during manual control, ensure smooth changeover. With switches 24, 26 set for manual control, the upper and lower limits for the process variable may each be indicated on meter 20 by adjusting potentiometer 36 and then operating the appropriate switch 40 or 42 so that potentiometer 44 or 55 may be set to its correct position at which the deviation indicated by meter 20 will be zero. The alarms may alternatively be operated by excessive output from amplifier 14, and the signal dependent on the process variable may be utilized when setting the limits. A suitable construction of indicator combined with control switches and potentiometers is described. 1,209,415.Fluidic pulse converters. HONEYWELL Inc. Feb. 21, 1969 [Feb. 23, 1968], No. 9488/69. Heading G3H. A pure fluid pulse converter comprises an amplifier 11 fed through a duct 20 with a pulsating input signal which is transmitted to control orifices 16, 15 by a short line 21 and a longer delay line 25 provided with a trombone slide 28 which is adjusted automatically in response to temperature variations sensed by a helical bi-metal element 30 in the path of the working fluid. Output limbs 13, 14 feed capacitances 35, 37 through resistors 36, 38 so that the difference in pressures in conduits 39, 40 varies as the frequency of the pulses applied to duct 20. As shown the amplifier is mono-stable with a preferred outlet 13, but in various modifications (not shown) abi-stable amplifier can be used, or the capacitances 35, 37, omitted so that the device forms a pulse shaper. The signal fed to duct 20 may be derived from a temperature responsive fluid oscillator (not shown) in the working fluid of a gas turbine.

Measuring variable state in extrusion of - glass fibres of constant diameter

Abstract: Variable process parameter is measured and the result is converted into a frequency signal A counter signal is fed in with a given frequency and is modulated with the frequency signal, to determine the frequency of the latter, in order to obtain the variable value