data1 = load('mat/data_001.mat', 't', 'x1', 'x2');
data2 = load('mat/data_002.mat', 't', 'x1', 'x2');

figure;
hold on;
plot(data1.t, data1.x1-data1.x2);
plot(data2.t, data2.x1-data2.x2);
hold off
xlabel('Time [s]');
ylabel('Voltage [V]');
legend({'Slip-ring OFF', 'Slip-ring ON'});