def get_R_theta(lockin):
    """Get R and Theta. (Measure).

    args:
            lockin (pyvisa.resources.gpib.GPIBInstrument): SRS830

    returns:
            (tuple): R, Theta




    """
    r, theta = lockin.query("SNAP? 3,4").split("\n")[0].split(",")
    r, theta = float(r), float(theta)
    return r, theta