Method and apparatus for direct measurement of percent

Claim 2

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said capacitance probe means, a variable gain a-c voltage generator connected in series with said reference capacitor and said capacitor probe means for applying an a-c voltge across said capacitor and probe means, voltage detecting means for detecting a change in the voltage differential across said probe means and controlling the gain of said a-c voltage generator for maintaining a predetermined a-c voltage applied across said probe means, and voltage measuring means for measuring the voltage differential applied across said reference capacitor as a measure of the percentage water content of the oil-water emulsion.

Claim 3

The apparatus as described in claim 1, wherein said voltage measuring means comprises first voltage measuring means connected between said a-c voltage generator and reference capacitor for measuring the total voltage differential applied across said reference capacitor and capacitance probe means and generating a signal representative thereof, second voltage measuring means connected between said reference capacitor and capacitance probe means for measuring the voltage differential applied across said capacitance probe means and generating a signal representative thereof, and difference means connected to said first and second voltage measuring means for subtracting said signal representative of the voltage differential across said reference capacitor and capacitance probe means and generating a signal representative of the voltage differential across said reference capacitor.

Claim 4

The apparatus as described in claim 2, wherein said voltage detecting means comprises an error measuring means the output of which is connected as a feedback loop to said a-c voltage generator, a variable resistor connected between a voltage source and a summing junction input to said error measuring means for generating a first current the magnitude of which is directly related to said predetermined a-c voltage differential desired to be maintained across said capacitance probe means, and a fixed resistor connected between the output of said second voltage measuring means and said summing junction input to said error measuring means for receiving said signal representative of the actual voltage differential across said capacitance probe means and generating a second current of opposite polarity to said first current which is directly related to the actual voltage differential across said capacitance probe means, said first and second currents being algebraically summed at said summing junction and applied as an input to said error measuring means for generating in response thereto an error feedback signal for controlling the gain of said a-c voltage generator to cause said actual voltage differential across said capacitance probe means to equal said desired predetermined a-c voltage differential.

Claim 5

The apparatus as described in claim 3, wherein said first voltage measuring means comprises a first voltage converter circuit for converting said total a-c voltage applied across said reference capacitor and said capacitance probe means to a d-c voltage signal.

Claim 6

The apparatus as described in claim 4, wherein said second voltage measuring means comprises an isolation amplifier connected between said reference capacitor and capacitance probe means for subtracting stray capacitance that may appear in parallel with said capacitance probe means and generating an a-c voltage output representative of said voltage differential applied across said capacitance probe means, and a second voltage converter circuit receiving said a-c voltage output of said isolation amplifier and converting said a-c voltage to a d-c voltage signal.

Claim 7

The apparatus as described in claim 5, wherein said difference means comprises a difference amplifier for receiving the d-c voltage outputs of said first and second voltage converter circuits and subtracting the d-c voltage outputs to obtain a d-c voltage differential signal directly representative of the percentage water content of the oil-water emulsion.

Claim 8

The apparatus as described in claim 6, wherein said error measuring means comprises an error amplifier having an input summing junction for receiving said first and second currents from said fixed and variable resistors.

Claim 9

The apparatus described in claim 1, further including function generator means receiving said measured voltage differential from said voltage measuring means and converting said voltage differential from a nonlinear to a linear function with respect to percentage water, and multiplying means for multiplying said voltage output from said function generator by a preselected value.

Claim 10

The apparatus described in claim 8, further including voltage to current conversion means to convert the multiplied d-c voltage signal output from said multiplying means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 11

The apparatus described in claim 1, further including first function generator means receiving said measured voltage differential from said voltage measuring means and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for a first portion of the percentage water range, second function generator means in parallel with said first function generator means receiving said measured voltage differential from said voltage measuring means and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for the remaining portion of the percentage water range, multiplying means in series with said second function generator means for multiplying said voltage output from said second function generator by a preselected value, and means for adding the voltage output from said first function generator means and said multiplying means.

Claim 12

The apparatus described in claim 10, further including voltage to current conversion means for converting the d-c voltage signal output from said adding means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 13

The apparatus described in claim 11, further including a plurality of function generator means for receiving said measured voltage differential from said voltage measuring means, each of said plurality of function generator means converting said voltage differential from a nonlinear to a linear function with respect to percentage water for a predetermined portion of the percentage water range, a multiplying means in series with at least one of said plurality of function generator means for multiplying said voltage output from said at least one of said function generator means by a preselected value, and means for adding the voltage output from said multiplying means and each of said remaining function generator means.

Claim 14

The apparatus as described in claim 12, further including voltage to current conversion means for converting the d-c voltage signal output from said adding means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 15

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said capacitance probe meAns, a variable gain a-c voltage generator connected in series with said reference capacitor and said capacitance probe means for applying an a-c voltage across said capacitor and probe means, calibrate control means for predetermining the a-c voltage desired to be maintained across said capacitance probe means, voltage detecting means for detecting a change in the voltage differential across said probe means and controlling the gain of said a-c voltage generator for maintaining said predetermined a-c voltage applied across said probe means, voltage measuring means for measuring the voltage differential applied across said reference capacitor as a measure of the percentage water content of the oil-water emulsion, and conversion means for converting said voltage differential from a nonlinear to a linear function representative of percentage water content of the oil-water emulsion.

Claim 16

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said capacitance probe meAns, a variable gain a-c voltage generator connected in series with said reference capacitor and said capacitance probe means for applying an a-c voltage across said capacitor and probe means, calibrate control means for predetermining the a-c voltage desired to be maintained across said capacitance probe means, voltage detecting means for detecting a change in the voltage differential across said probe means and controlling the gain of said a-c voltage generator for maintaining said predetermined a-c voltage applied across said probe means, voltage measuring means for measuring the voltage differential applied across said reference capacitor as a measure of the percentage water content of the oil-water emulsion, and conversion means for converting said voltage differential from a nonlinear to a linear function representative of percentage water content of the oil-water emulsion.

Claim 17

The apparatus as described in claim 14, wherein said voltage measuring means comprises a first voltage converter circuit connected between said a-c voltage generator and reference capacitor for measuring the total a-c voltage differential applied across said reference capacitor and capacitance probe means and converting said a-c voltage differential to a d-c voltage signal, an isolation amplifier connected between said reference capacitor and capacitance probe means for subtracting stray capacitance that may appear in parallel with said capacitance probe means and generating an a-c voltage output representative of said voltage differential applied across said capacitance probe means, a second voltage converter circuit receiving said a-c voltage output of said isolation amplifier and converting said a-c voltage to a d-c voltage signal, and a difference amplifier for receiving the d-c voltage outputs of said first and second voltage converter circuits and subtracting the d-c voltage outputs to obtain a d-c voltage differential signal directly representative of the percentage water content of the oil-water emulsion.

Claim 18

The apparatus as described in claim 15, wherein said calibrate control means comprises a variable resistor connected between a voltage source and input summing junction of said voltage detecting means for producing a first current the magnitude of which is directly related to said predetermined a-c voltage differential desired to be maintained across said capacitance probe means.

Claim 19

The apparatus as described in claim 16, wherein said voltage detecting means comprises an error amplifier having said input summing junction and an output which is connected as a feedback loop to said a-c voltage generator, and a fixed resistor connected between the output of said second voltage converter circuit and said input summing junction of said error amplifier for receiving said voltage signal representative of the actual voltage differential across said capacitance probe means and producing a second current of opposite polarity to said first current, the magnitude of which is directly related to the actual voltage differential across said capacitance probe means, said first and second currents being algebraically summed at said summing junction and applied as an input to said error measuring means for generating in response thereto an error feedback signal for controlling the gain of said a-c voltage generated to cause said actual voltage differential across said capacitance probe means to equal said desired predetermined a-c voltage differential.

Claim 20

The apparatus described in claim 14, wherein said conversion means comprises function generator means receiving said measured voltage differential from said voltage measuring means and converting said voltage differential from a nonlinear to a linear function with respect to percentage water, and multiplying means for multiplying said voltage output from said function generator by a preselected value.

Claim 21

The apparatus described in claim 18, further Including voltage to current conversion means to convert the multiplied d-c voltage signal output from said multiplying means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 22

The apparatus described in claim 14, wherein said conversion means comprises first function generator means receiving said measured voltage differential from said voltage measuring means and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for a first portion of the percentage water range, second function generator means in parallel with said first function generator means receiving said measured voltage differential from said voltage measuring means and converting said voltage differential from a nonlinear to a linear function with respect to percentage of water for the remaining portion of the percentage water range, multiplying means in series with said second function generator means for multiplying said voltage output from said second function generator by a preselected value, and means for adding the voltage output from said first function generator means and said multiplying means.

Claim 23

The apparatus described in claim 20, further including voltage to current conversion means for converting the d-c voltage signal output from said adding means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 24

The apparatus described in claim 14, wherein said conversion means comprises a plurality of function generator means for receiving said measured voltage differential from said voltage measuring means, each of said plurality of function generator means converting said voltage differential from a nonlinear to a linear function with respect to percentage water for a predetermined portion of the percentage water range, a multiplying means in series with at least one of said plurality of function generator means for multiplying said voltage output from said at least one of said function generator means by a preselected value, and means for adding the voltage output from said multiplying means and each of said remaining function generator means.

Claim 25

The apparatus as described in claim 22, further including voltage to current conversion means for converting the d-c voltage signal output from said adding means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 26

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said capacitance probe means, an a-c voltage generator connected in series with said reference capacitor and said capacitance probe means for applying an a-c voltage across said capacitor and probe means, calibrate control means for predetermining the a-c voltage desired to be maintained across said capacitance probe means, variable gain means connected to said a-c voltage generator for detecting a change in the actual voltage differential across said probe means and controlling the gain of said a-c voltage generator for attempting to maintain said predetermined a-c voltage applied across said probe means, voltage measuring means for measuring the voltage differential applied across said reference capacitor as a measure of the percentage water content of the oil-water emulsion, and function conversion means for converting said voltage differential from a nonlinear to a linear function representative of percentage water content of the oil-water emulsion.

Claim 27

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said capacitance probe means, an a-c voltage generator connected in series with said reference capacitor and said capacitance probe means for applying an a-c voltage across said capacitor and probe means, calibrate control means for predetermining the a-c voltage desired to be maintained across said capacitance probe means, variable gain means connected to said a-c voltage generator for detecting a change in the actual voltage differential across said probe means and controlling the gain of said a-c voltage generator for attempting to maintain said predetermined a-c voltage applied across said probe means, voltage measuring means for measuring the voltage differential applied across said reference capacitor as a measure of the percentage water content of the oil-water emulsion, and function conversion means for converting said voltage differential from a nonlinear to a linear function representative of percentage water content of the oil-water emulsion.

Claim 28

The apparatus as described in claim 24, wherein said voltage measuring means comprises a first voltage converter circuit connected between said a-c voltage generator and reference capacitor foR measuring the total a-c voltage differential applied across said reference capacitor and capacitance probe means and converting said a-c voltage differential to a d-c voltage signal, an isolation amplifier connected between said reference capacitor and capacitance probe means for subtracting stray capacitance that may appear in parallel with said capacitance probe means and generating an a-c voltage output representative of said voltage differential applied across said capacitance probe means, a second voltage converter circuit receiving said a-c voltage output of said isolation amplifier and converting said a-c voltage to a d-c voltage signal, and a difference amplifier for receiving the d-c voltage outputs of said first and second voltage converter circuits and subtracting the d-c voltage outputs to obtain a d-c voltage differential signal directly representative of the percentage water content of the oil-water emulsion.

Claim 29

The apparatus as described in claim 24, wherein said calibrate control means comprises a variable resistor connected between a voltage source and an input summing junction of said variable gain means for producing a first current the magnitude of which is directly related to said predetermined a-c voltage differential desired to be maintained across said capacitance probe means.

Claim 30

The apparatus as described in claim 26, wherein said variable gain means comprises a variable gain connected between said a-c voltage generator and said reference capacitor for controlling the gain of said a-c voltage generator, an error amplifier having said input summing junction and an output which is connected as a feedback loop to said variable gain circuit, and a fixed resistor connected between the output of said second voltage converter circuit and said input summing junction of said error amplifier for receiving said signal representative of the voltage differential across said capacitance probe means and producing a second current of a polarity opposite to that of said first current, the magnitude of which is directly related to the actual voltage differential across said capacitance probe means, said error amplifier subtracting said first and second currents and generating in response thereto an error feedback signal for controlling the operation of said variable gain circuit to cause said actual voltage differential across said probe means to coincide with said predetermined voltage differential.

Claim 31

The apparatus described in claim 24, wherein said function conversion means comprises a first function generator means receiving said measured voltage differential from said voltage measuring means and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for a first portion of the percentage water range, second function generator means in parallel with said first function generator means receiving said measured voltage differential from said voltage measuring means and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for the remaining portion of the percentage water range, multiplying means in series with said second function generator means for multiplying said voltage output from said second function generator by a preselected value, and means for adding the voltage output from said first function generator means and said multiplying means.

Claim 32

The apparatus described in claim 28, further including voltage to current conversion means for converting the d-c voltage signal output from said adding means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 33

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said caPacitance probe means, a variable gain a-c voltage generator connected in series with said reference capacitor and said capacitance probe means for applying an a-c voltage across said capacitor and probe means, first voltage measuring means connected between said a-c voltage generator and reference capacitor for measuring the total voltage differential applied across said reference capacitor and capacitance probe means and generating a signal representative thereof, second voltage measuring means connected between said reference capacitor and capacitance probe means for measuring the voltage differential applied across said capacitance probe means and generating a signal representative thereof, difference means connected to said first and second voltage measuring means for subtracting said signal representative of the voltage differential across said probe means from said signal representative of the total voltage differential across said reference capacitor and capacitance probe means and generating a signal representative of the voltage differential across said reference capacitor, said voltage differential across said reference capacitor being a measure of the percentage water content of the oil-water emulsion, error measuring means the output of which is connected as a feedback loop to said a-c voltage generator, a fixed resistor connected between the output of said second voltage measuring means and said error measuring means for receiving said signal representative of the voltage differential across said capacitance probe means and generating a first current the magnitude of which is directly related to the actual voltage differential across said capacitance probe means, and a variable resistor connected between a source of predetermined voltage and said error measuring means for generating a second current of polarity opposite to said first current, the magnitude of which is directly related to said predetermined a-c voltage differential desired to be maintained across said capacitance probe means, said error measuring means subtracting said first and second currents and generating in response thereto an error feedback signal applied to said a-c voltage generator for controlling the gain of said a-c voltage generator to cause said actual voltage differential across said probe means to coincide with said predetermined voltage differential.

Claim 34

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said caPacitance probe means, a variable gain a-c voltage generator connected in series with said reference capacitor and said capacitance probe means for applying an a-c voltage across said capacitor and probe means, first voltage measuring means connected between said a-c voltage generator and reference capacitor for measuring the total voltage differential applied across said reference capacitor and capacitance probe means and generating a signal representative thereof, second voltage measuring means connected between said reference capacitor and capacitance probe means for measuring the voltage differential applied across said capacitance probe means and generating a signal representative thereof, difference means connected to said first and second voltage measuring means for subtracting said signal representative of the voltage differential across said probe means from said signal representative of the total voltage differential across said reference capacitor and capacitance probe means and generating a signal representative of the voltage differential across said reference capacitor, said voltage differential across said reference capacitor being a measure of the percentage water content of the oil-water emulsion, error measuring means the output of which is connected as a feedback loop to said a-c voltage generator, a fixed resistor connected between the output of said second voltage measuring means and said error measuring means for receiving said signal representative of the voltage differential across said capacitance probe means and generating a first current the magnitude of which is directly related to the actual voltage differential across said capacitance probe means, and a variable resistor connected between a source of predetermined voltage and said error measuring means for generating a second current of polarity opposite to said first current, the magnitude of which is directly related to said predetermined a-c voltage differential desired to be maintained across said capacitance probe means, said error measuring means subtracting said first and second currents and generating in response thereto an error feedback signal applied to said a-c voltage generator for controlling the gain of said a-c voltage generator to cause said actual voltage differential across said probe means to coincide with said predetermined voltage differential.

Claim 35

The apparatus as described in claim 30, wherein said first voltage measuring means comprises a first voltage converter circuit for converting said total a-c voltage applied across said reference capacitor and said capacitance probe means to a d-c voltage signal.

Claim 36

The apparatus as described in claim 30, wherein said second voltage measuring means comprises an isolation amplifier connected between said reference capacitor and capacitance probe means for subtracting stray capacitance that may appear in parallel with said capacitance probe means and generating an a-c voltage output representative of said voltage differential applied across said capacitance probe means, and a second voltage converter circuit receiving said a-c voltage output of said isolation amplifier and converting said a-c voltage to a d-c voltage signal.

Claim 37

The apparatus as described in claim 30, wherein said difference means comprises a difference amplifier for receiving the d-c voltage outputs of said first and second voltage converter circuits and subtracting the d-c voltage outputs to obtain a d-c voltage differential signal directly representative of the percentage water content of the oil-water emulsion.

Claim 38

The apparatus as described in claim 30, wherein said error measuring means comprises an error amplifier having an input summing junction for receiving said first and second currents from said fixed and variable resistors.

Claim 39

The apparatus described in claim 30, further including function generator means receiving said measured voltage differential from said dIfference means and converting said voltage differential from a nonlinear to a linear function with respect to percentage water, and multiplying means for multiplying said voltage output from said function generator by a preselected value.

Claim 40

The apparatus described in claim 35, further including voltage to current conversion means to convert the multiplied d-c voltage signal output from said multiplying means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 41

The apparatus described in claim 30, further including a plurality of function generator means for receiving said measured voltage differential from said difference means, each of said plurality of function generator means converting said voltage differential from a nonlinear to a linear function with respect to percentage water for a predetermined portion of the percentage water range, a multiplying means in series with at least one of said plurality of function generator means for multiplying said voltage output from said at least one of said function generator means by a preselected value, and means for adding the voltage output from said multiplying means and each of said remaining function generator means.

Claim 42

The apparatus as described in claim 37, further including voltage to current conversion means for converting the d-c voltage signal output from said adding means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 43

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said capacitance probe means, a variable gain a-c voltage generator connected in series with said reference capacitor and said capacitance probe means for applying an a-c voltage across said capacitor and probe means, a first voltage converter circuit connected between said a-c voltage generator and reference capacitor for measuring the total a-c voltage differential applied across said reference capacitor and capacitance probe means and converting said a-c voltage differential to a d-c voltage signal, an isolation amplifier connected between said reference capacitor and capacitance probe means for subtracting stray capacitance that may appear in parallel with said capacitance probe means and generating an a-c voltage output representative of said voltage differential applied across said capacitance probe means, a second voltage converter circuit receiving said a-c voltage output of said isolation amplifier and converting said a-c voltage to a d-c voltage signal, a difference amplifier for receiving the d-c voltage outputs of said first and second voltage converter circuits and subtracting the d-c voltage outputs to obtain a d-c voltage differential signal directly representative of the percentage water content of oil-water emulsion, an error amplifier having an input summing junction and an output which is connected as a feedback loop to said a-c voltage generator, a fixed resistor connected between the output of said second voltage converter circuit and said input summing junction of said error amplifier for receiving said signal representative of the voltage differential across said capacitance probe means and producing a first current the magnitude of which is directly related to the actual voltage differential across said capacitance probe means, a variable resistor connected between a source of predetermined voltage and said input summing junction of said error amplifier for producing a second current of polarity opposite to that of said first current, the magnitude of which is directly related to said predetermined a-c voltage differential sought to be maintained across said capacitance probe means, said error amplifier Algebraically adding said first and second currents and generating in response thereto an error feedback signal for controlling the gain of said a-c voltage generator to cause said actual voltage differential to coincide with said predetermined voltage differential, first function generator means receiving said measured voltage differential from said difference amplifier and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for a first portion of the percentage water range, second function generator means in parallel with said first function generator means receiving said measured voltage differential from said difference amplifier and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for the remaining portion of the percentage water range, multiplying means in series with said second function generator means for multiplying said voltage output from said second function generator by a preselected constant, means for adding the voltage output from said first function generator means and said multiplying means, and voltage to current conversion means for converting the d-c voltage signal output from said adding means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.

Claim 44

Apparatus for measuring the percentage water content of an oil-water emulsion, comprising capacitance probe means for measuring the capacitance of the oil-water emulsion, a reference capacitor of known value connected in series with said capacitance probe means, a variable gain a-c voltage generator connected in series with said reference capacitor and said capacitance probe means for applying an a-c voltage across said capacitor and probe means, a first voltage converter circuit connected between said a-c voltage generator and reference capacitor for measuring the total a-c voltage differential applied across said reference capacitor and capacitance probe means and converting said a-c voltage differential to a d-c voltage signal, an isolation amplifier connected between said reference capacitor and capacitance probe means for subtracting stray capacitance that may appear in parallel with said capacitance probe means and generating an a-c voltage output representative of said voltage differential applied across said capacitance probe means, a second voltage converter circuit receiving said a-c voltage output of said isolation amplifier and converting said a-c voltage to a d-c voltage signal, a difference amplifier for receiving the d-c voltage outputs of said first and second voltage converter circuits and subtracting the d-c voltage outputs to obtain a d-c voltage differential signal directly representative of the percentage water content of oil-water emulsion, an error amplifier having an input summing junction and an output which is connected as a feedback loop to said a-c voltage generator, a fixed resistor connected between the output of said second voltage converter circuit and said input summing junction of said error amplifier for receiving said signal representative of the voltage differential across said capacitance probe means and producing a first current the magnitude of which is directly related to the actual voltage differential across said capacitance probe means, a variable resistor connected between a source of predetermined voltage and said input summing junction of said error amplifier for producing a second current of polarity opposite to that of said first current, the magnitude of which is directly related to said predetermined a-c voltage differential sought to be maintained across said capacitance probe means, said error amplifier Algebraically adding said first and second currents and generating in response thereto an error feedback signal for controlling the gain of said a-c voltage generator to cause said actual voltage differential to coincide with said predetermined voltage differential, first function generator means receiving said measured voltage differential from said difference amplifier and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for a first portion of the percentage water range, second function generator means in parallel with said first function generator means receiving said measured voltage differential from said difference amplifier and converting said voltage differential from a nonlinear to a linear function with respect to percentage water for the remaining portion of the percentage water range, multiplying means in series with said second function generator means for multiplying said voltage output from said second function generator by a preselected constant, means for adding the voltage output from said first function generator means and said multiplying means, and voltage to current conversion means for converting the d-c voltage signal output from said adding means to a direct current the magnitude of which is representative of the percentage water content of the oil-water emulsion.