The OPB350 Series of fluid sensor products now includes large tubing with outside diameters of 0.187 and 0.250 in. Providing engineers a non-contact way to detect fluid, the line also features an alternate plastic housing that offers a robust connection mechanism to the PC board. The housing is designed to alleviate the stress that large-diameter tubing can put on the sensors. The devices use an IR LED/phototransistor pair to determine the difference in refractive properties between full and empty tubing as it passes through the housing. The sensors generate an output signal that can be read by external reference circuitry to describe multiple output states, such as “fluid present,” “no fluid present,” and “no tube present,” as well as specialized functions like bubble detection. The IR LED and silicon photodetector are housed in an opaque plastic housing that shields the optical components from ambient light. The housing features an opening designed to accommodate clear tubing with outside diameters of 0.125 in. (3.18 mm), 0.187 in. (4.77 mm), or 0.25 in. (6.36 mm). Engineers can use smaller tubes with outside diameters of less than 0.125 in. with OPB350 sensors if the tube can be “sized up” to one of the standard sizes by using a length of the larger tubing as an adapter. The IR input LED features forward dc current of 100 mA (peak current of 1.0 A, 1 µs pulse, 330 pps), with reverse dc voltages up to 2 V and power dissipation of 100 mW. The output phototransistor offers collector-emitter voltage of 30 V and emitter-collector voltage of 5 V. Collector dc current is 50 mA with 100 mW of power dissipation. Operating temperature ranges from -40° to +85°C. Designed for secure PC board mounting, the larger-diameter OPB350 housing measures 1.165 x 0.30 in. (29.59 x 7.62 mm) with a board-mounted profile of 0.525 in. (13.34 mm). Two 0.125-in. mounting holes accommodate screws and other fasteners for mounting the device to the PC board. Color-coded 24-in. 26 AWG wires identify the anode, cathode, emitter, and collector to ensure proper positioning in the circuit. Typical pricing ranges from $3.79 to $5.15 in quantities of 1,000.