Ruby Electronics DT-8890 Digital Differential Air Vapor Pressure Meter Gauge Manometer with USB port Large dual LCD with back light Max / Min / Avg value with relative time stamp Differential pressure Range +/- 5 PSI (+ 138.3 inH2O) Mini USB port for uploading measurement data to the computer via USB cable (included) Optional Windows software is included for FREE (Note: the software is included AS IS. No software development kit or support available).