# Voltage Monitor Circuit Test Results

## Contents

- Voltage Transfer Function
- Frequency Analysis of the Filter Designed for PowerBuoy Voltage and Current Sensing

## Voltage Transfer Function

This test used a lab supply to test the total transfer (filter included) for the voltage ranges from 0 to 333, which was the upper limit of the power supply.

    close all; clear;

    Vin = [ 0 20.3 40.0 60.0 80.8 100.5 120.2 140.9 160.6 180.5 200.3 220.8 ...
        240.7 260.6 280.7 300.8 320.8 333.5];

    Vout = [0.0 0.0 0.120 0.270 0.440 0.590 0.750 0.918 1.07 1.23 1.39 1.55 ...
        1.72 1.88 2.08 2.21 2.38 2.47];

    VoFilt = [0.020 0.178 0.335 0.494 0.658 0.811 0.966 1.13 1.29 1.44 1.60 ...
        1.77 1.92 2.08 2.25 2.41 2.58 2.68];

    % Fit a line
    [p, S] = polyfit(Vin,Vout,1)
    [pf,Sf] = polyfit(Vin, VoFilt,1);
    figure;
    plot (Vin, (p(1)*Vin+p(2)),'b-', ...
        Vin, (pf(1)*Vin + pf(2)),'g-',...
        Vin, Vout, 'b.', ...
        Vin, VoFilt,'g.');
    xlabel('Input Voltage (V)');
    ylabel('Output Voltage (V)');
    legend(['V_{OUT} = ' num2str(p(1)) 'V_{IN} + ' num2str(p(2))],...
        ['V_{OUTFILT} = ' num2str(pf(1)) 'V_{IN} + ' num2str(pf(2))],'Location','SouthEast');
    title('Voltage Sense Circuit Response');
    grid on;

    p =

        0.0078   -0.1625

    S =

            R: [2x2 double]
           df: 16
        normr: 0.1935

## Frequency Analysis of the Filter Designed for PowerBuoy Voltage and Current Sensing

First define the frequencies measured:

    f = [1 100:100:900 1e3:1e3:18e3];

    % Single input was sinusoidal, offset by 600mV and Vpp was:

    Vpp = 2.14;

    % Now enter the results (Vpp)

    VoutPP = [2.18 2.14 2.14 2.16 2.16 2.16 2.18 2.18 2.2 2.22 2.24 2.40 ...
        1.16 0.40 0.18 0.12 0.08 0.06 .016 0.012 0.010 0.0076 0.0060     ...
        0.0046 0.0038 0.0032 0.0032 0.0030];

    % Enter Phase Difference (Degrees

    Phase = [ 2.1 3.4 11.5 17 23 27 32 40 45 50 57 131.5 135 180+95 180+74 180+63 180+50 0 0 0 0 0 0 0 0 0 0 0 ];

    % Calculate the gain

    Gain = 20*log10(VoutPP./Vpp);

    figure
    subplot(211);

    semilogx(f,Gain,'.-');
    grid on;
    ylabel('Voltage Gain (dB)');
    title('Filter Frequency Response for 2V Peak-Peak Positive Sinusoid');
    subplot(212);
    semilogx(f,Phase,'.-');
    ylabel('Phase (deg)');
    xlabel('Frequency (Hz)');
    grid on