A lumbar support pillow for supporting the lumbar spine of a person. The absorbent chassis defines a pair of laterally opposed side edges and a pair of longitudinally opposed waist edges. The integral spring is produced with a wire EDM technique and can be symmetrical or asymmetrical around its periphery as a way of offsetting off-center impact from the bottom of the flow tube. The sheath fluid flows through the fluid passage, having a first velocity as it passes the point the specimen fluid is injected. Part of the period during which the light of the first spectral band is extracted overlaps with the period during which the light of the third spectral band is extracted, and part of the period during which the light of the second spectral band is extracted overlaps with the period during which the light of the fourth spectral band is extracted. A microcontroller is coupled to the envelope modulator for providing an envelope signal to the envelope modulator and a low pass filter is coupled to the envelope modulator for receiving a modulated command from the envelope modulator.