Industrial and scientific apparatus, namely, a spectrometer for measuring, detecting, sensing, monitoring, controlling, and/or regulating mass flux, density, surface area, velocity, acceleration, current, voltage, resistance, temperature, pressure, particle concentration, kinematic viscosity, dynamic viscosity, mass, momentum, time, force, torque, energy, heat conduction, heat convection, stress, strain, or work of matter in a thermodynamic system or components thereof, and replacement parts ...