Apparatus and method determining the value of a capacitance
First Claim
1. An electrical circuit useful in determining the value of a capacitor including:
- a first bilateral switch for flowing a charging current through a resistive element to an initially-depleted first capacitor of known value, thereby charging said first capacitor to the potential of a voltage reference over a resulting first time;
a second bilateral switch for flowing a charging current through said resistive element to an initially depleted second capacitor, thereby charging said second capacitor to said potential over a resulting second time, and;
means for determining said times.
1 Assignment
0 Petitions
Accused Products
Abstract
An apparatus useful in determining the value of a capacitor includes a first bilateral switch for flowing a charging current through a resistive element to an initially-depleted first capacitor of known value. The first capacitor is thereby charged to the potential of a trigger reference over a resulting first time period. A second bilateral switch is provided for flowing a charging current through the same resistive element to an initially-depleted second capacitor, thereby charging it to the potential of the same trigger reference over a resulting second time period. A device such as an oscilloscope or frequency counter is used for determining these time periods and the value of the unknown second capacitor may thereupon be computed using disclosed formulas.
A method for determining the value of a capacitor includes the steps of flowing a charging current through a resistive element to an initially-depleted first capacitor of known value, thereby charging this capacitor to the potential of a trigger reference over a resulting first time period. A charging current is then caused to flow through the same resistive element to an initially-depleted second capacitor for charging it to the potential of the trigger reference over a resulting second time period. The value of the second capacitor is then computed by utilizing the first time period, the second time period and the value of the first capacitor.
-
Citations
14 Claims
-
1. An electrical circuit useful in determining the value of a capacitor including:
-
a first bilateral switch for flowing a charging current through a resistive element to an initially-depleted first capacitor of known value, thereby charging said first capacitor to the potential of a voltage reference over a resulting first time; a second bilateral switch for flowing a charging current through said resistive element to an initially depleted second capacitor, thereby charging said second capacitor to said potential over a resulting second time, and; means for determining said times. - View Dependent Claims (2, 3)
-
-
4. A circuit useful in determining the value of a capacitor and including:
-
a charging source including a resistive element; a plurality of switches, each switch being positionable between a first, open position and a second, closed position in response to logic signals, said switches thereby being controllable for sequentially connecting a first reference capacitor of known value and a second capacitor to said resistive element for charging said capacitors to a potential; a voltage reference for establishing a trigger reference voltage and generating a clocking pulse when the sequentially detected charge potential of said capacitors is equal to said trigger reference voltage; a logic network for generating said logic signals in response to said clocking pulse, and; means for determining a first time required to charge said first capacitor from an initially-depleted state to said trigger reference voltage and for determining a second time required to charge said second capacitor from an initially-depleted state to said trigger reference voltage. - View Dependent Claims (5)
-
-
6. A method for determining the value of a capacitor including the steps of:
-
flowing a charging current through a resistive element to an initially-depleted first capacitor of known value for charging said first capacitor to the potential of a voltage reference over a resulting first time; flowing a charging current through said resistive element to an initially-depleted second capacitor for charging said second capacitor to said potential of said voltage reference over a resulting second time, and; computing the value of said second capacitor by utilizing said first time, said second time and the value of said first capacitor. - View Dependent Claims (7, 8)
-
-
9. A method for determining the value of a capacitor including the steps of:
-
providing a source of charging voltage having a resistive element coupled in series therewith; connecting an initially-depleted reference capacitor to said resistive element at a first time for charging said reference capacitor to a reference voltage; generating a first clocking pulse when said reference capacitor is charged to said reference voltage; connecting an initially-depleted second capacitor to said resistive element at a second time for charging said second capacitor to said reference voltage; generating a second clocking pulse when said second capacitor is charged to said reference voltage; measuring the elapsed times between said first time and said first clocking pulse and between said first clocking pulse and said second clocking pulse; and
;computing a duty cycle utilizing said elapsed times. - View Dependent Claims (10, 11, 12, 13)
-
-
14. A method for determining the value of a capacitor including the steps of:
-
providing a first, charge-depleted reference capacitor of known value and a second capacitor of unknown value; providing a charging source including a resistive element for sequentially charging said capacitors to the potential of a voltage reference; providing a voltage reference having a predetermined trigger reference voltage for generating a clocking pulse when the charge potential of one of said capacitors is equal to said trigger reference voltage, said clocking pulse having a rising edge; providing a logic network for generating logic signals in response to said clocking pulse; providing a plurality of bilateral switches, each of which is responsively positionable by a logic signal; closing a first bilateral switch for connecting said reference capacitor to said resistive element at a first time and substantially simultaneously closing a fourth bilateral switch for connecting said second capacitor to a point of ground potential; generating a first clocking pulse when the charge potential of said reference capacitor is equal to said trigger reference voltage; determining the elapsed time T1 between said first time and the rising edge of said first clocking pulse; generating first logic signals in response to said rising edge of said first clocking pulse; closing a third bilateral switch for connecting said reference capacitor to said point of ground potential and substantially simultaneously opening said fourth bilateral switch, both in response to said first logic signals; opening said first bilateral switch and substantially simultaneously closing a second bilateral switch, both in response to said first logic signals, said closure of said second switch thereby connecting said second capacitor to said resistive element; generating a second clocking pulse when the charge potential of said second capacitor is equal to said trigger reference voltage; determining the elapsed time T2 between said rising edge of said first clocking pulse and the rising edge of said second clocking pulse; computing a duty cycle D in accordance with the formula D=T2 divided by (T1+T2), and; computing the value of said second capacitor in accordance with the formula C3=(D)(C2) divided by (1-D).
-
Specification