Logarithmic resistance-to-frequency converter
AssigneeU.S. Philips Corporation
InventorDietrich Meyer Ebrecht
Life of this patent
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Abstract
By including four resistors and a capacitor in a bridge and connecting the bridge to the input terminals and the output terminals of a comparator amplifier a relaxation oscillator is obtained the square-wave frequency of which depends logarithmically upon the ratio of two resistances. Linearization is obtained by using a measuring-value transducer the resistance of which depends exponentially upon a physical quantity, such as temperature, as one of the resistors. The converter may be used in frequency-analog transmission of measuring values and in measuring instruments for measuring-value indication without the need for linearizing steps.
Claims9
A logarithmic resistance-to-frequency converter which produces a square-wave signal whose period is proportional to the natural logarithm of a resistance ratio comprising, a comparator amplifier having two input terminals and two output terminals, a first resistor, a second resistor connected in series with said first resistor to form first and second arms of a bridge circuit with said resistance ratio being determined by the resistance ratio of said first and second resistors, a third resistor, a fourth resistor, a capacitor, means connecting the third resistor in circuit to form a third arm of the bridge and the series combination of said fourth resistor and said capacitor as the fourth arm of the bridge, means connecting the bridge input terminals to the comparator amplifier output terminals and the bridge output terminals to the comparator amplifier input terminals so that the junction of the first and second bridge arms supplies a positive feedback voltage to the comparator amplifier input terminal to which it is connected whereby the circuit arrangement will self-oscillate to produce a square-wave signal at the comparator amplifier output terminals whose period varies as the natural logarithm of the resistance ratio of said first and second resistors.
A logarithmic converter which produces a square wave signal whose period is proportional to the natural logarithm of a resistance ratio comprising, a voltage comparator having two input terminals and two output terminals and means responsive to the zero passage of the voltages at the two input terminals for switching the voltage at the two output terminals between first and second fixed values of voltage, a first resistor, a second resistor connected in series with said first resistor to form first and second arms of a bridge circuit with said resistance ratio being determined by the resistance ratio of said first and second resistors, third and fourth resistors having the same value of resistance, a capacitor, means connecting the third resistor in circuit to form a third arm of the bridge and the series combination of said fourth resistor and said capacitor as the fourth arm of the bridge, means connecting the bridge input terminals to the voltage comparator output terminals and the bridge output terminals to the voltage comparator input terminals so that the circuit arrangement will self-oscillate to produce a square-wave signal at the voltage comparator output terminals whose period varies as the natural logarithm of the resistance ratio of said first and second resistors.
Dependencies are inferred from the claim text.