US2397540A - Ratio circuit - Google Patents

Description

April 2, 1946. R. g. DOME 2,397,540

I I RATIO cmcun Filed Sept. 21, 1945 PULSE. GENERATOR INSTANTANEOUS CURRENT THROUG flEV/CE 6 I? AVERAGED OVER A CYCLE BY INTEGRAT/NE FFEC7' 0F AMMETER Z Z I l l Inventor: Robert B. Dome;

His Attorney.

Patented Apr. 2, 19 ,6

5 PATENT FFICE f nA'n'o cmomr Robert B. Dome, Bridgeport, Conn., asslgnor to General Electric Comp New York any, a corporation of- Application September 21, 1943, Serial No. 503,304

6 Claims.

The present invention relates to circuits for measuring the ratio of two voltages.

An object oi m invention is to provide an improved ratio circuit whi varying voltages.

ch will handle rapidly The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. l is a circuit diagram and Fig. 2 is a diagram explaining the operation,

Referring to the drawing there is shown a ratio circuit having terminals I, 2 to which are applied the voltages E1, E2 whose ratio is to be determined. The terminals E1 are connected across a saw-tooth circuit comprising a resistance 3 and a condenser 4, the condenser being shunted by a discharge device 5 keyed by a pulse generator 6 to short circuit the condenser at intervals determined b the keying pulse repetition rate. The condenser and resistance are related to the repetition rate so that the voltage across the condenser starts from zero at the end 01' each keying pulse and increases linearl to a maximum immediately preceding the succeeding keying pulse, thus converting the voltage E1 to a saw-tooth voltage having a magtitude equal to hint. The saw-tooth voltage is applied to the control grid 1 of a gaseous discharge device 8 having an anode 9 and a cathode I0 connected in series with resistances II, I2 and a source of constant voltage I3. The voltage E2 is connected across a voltage divider I4 having a tap I-5 applying a fraction 162132 of this voltage to the cathode I0. A- potentiometer I 5a between the tap I5 and the oathode adjusts the cathode potential to a value such that when both voltages E1 and E2 are zero, the

device 8 is on the verge of'firing. When El and E2 have some positive value, the net change in bias on the device is, equal to the instantaneous difference of the saw-tooth voltage applied to the grid (kiElt) and the voltage applied to the oathode (kzEz). Since the device 8 is normally nonconducting. it is obvious that, by proper choice of the constants in and 702, for some values of time less than the interval between keying pulses, kiEit will be slightly greater than kzEz and the device 8 will fire due to the net positive change in bias. The time of firing, as apparent from Fig. 2, will be a measure of the ratio of the voltages E1 and E2. Once the device 8 has fired. the

current through the device is constant and is not subject to control by the grid bias until the current has been reduced below-the ionization value. This is accomplished by a device I6 connected across the resistance I2 and the voltage supply I3 and having acontrol grid I1 connected to the keying pulse generator. The device I6 is normally biased off and is biased on during each keying pulse, reducing the voltage at terminal I8 below the ionization value. The device 8 accordingly conducts only during that part of the interval between keying pulses during which kzEz is equal to or less than kiEit. Since the device 8 when conducting conducts at constant current, an ammeter reading the average current through the device will indicate the ratio of kzEz/lciElt up to the point at which 102% is greater than lciEi.

From this point on, there is an ambiguity since IczEz is never less than k1E1t and the device 8 is always biased oil. This ambiguity can be avoided by interchanging the voltages, i. e., by connecting E2 to terminals I and E1 to terminals 2. lower diagram of Fig. 2 shows the instantaneous current through device 8 by the solid line block and the average of this block over a cycle by the dashed line. Due to the mass of the meter movement, an ammeter will, by its inherent integrating properties, give a reading proportional to the dashed line.

In the use of the ratio circuit, 1) with both E1 and E2 disconnected, the potentiometer lid is adjusted to a value such that the device 8 is on the verge of firing; (2) with a known value of E1 connected to terminals I, and E2 disconnected, the resistance II is adjusted to cause full scale deflection of the ammeter I9; and (3) with a:

interchanging the voltages to obtain (instead of the ratio E2/ E1) the ratio Ei/Ez.

While I have shown particular embodiments of my invention, it will be understood that many modifications ma be made without departing from the spirit thereof, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

The-

i What I claim as new and desire tolsecure by Letters Patent oi the United States is:

1. A ratio circuit for measuringthe ratio of two'voltages comprising, a bias controlled de vice, means for converting one of the voltages to be compared to a voltage varying linearly with time and directly with the magnitude of the voltasoasso v ing linearly with time. and directly with age, means for biasing said device in accordance with theinsta'ntaneous diilerence ofsaid time varying voltage and the other voltage to be compared in such a manner that the time said device conducts depends upon the magnitude of said instantaneous diilerence, and means for utilizing the time said deviceconducts to determine the ratio of said two voltages. I

2. A ratio circuit for measuring the ratio of two voltages comprising, a grid controlled gaseous discharge device normally biased oil, a con stant voltage supply circuit for the device, means for converting one of the voltages to be compared to a voltage varying linearly with time .and' directly with the magnitude of the voltage, means I tude, and means for utilizing the time when the converted voltage and said second voltage have a predetermined relative value as a measure of the ratio of said twoyoltage's.

4. A ratio circuit for measuring the ratio oi two voltages comprising, means for converting one of said voltages to a saw-tooth voltage varyinglinearly with time and directly with magnitude, and means responsive to the difference" of said converted voltage and saidsecond voltage for indicating the ratio or said two voltages.

1 5. A ratio circuit for measuring the ratio of two voltages comprising, means for converting one of said voltages to a saw-tooth voltage varying'linearly with time and directly with magni tudefand'means responsive to the time when said i I converted voltage'and said second voltage have a predetermined relative value for indicating the ratio of said two voltages. 1 6. A ratio circuit for measuring the ratio of two voltages comprising, means for. converting one of said voltages to a voltage varying in magnitude in accordance with time and with the lation of said converted voltage to said other volt- Xtion of said converted voltage to said other volt age for determining the age varies with time,-and means responsive to v the time of occurrence of a predetermined relaratio of said voltages.

ROBERT B. DOME- magnimagnitude or said one voltage whereby the re-'

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