Scientific, analytical, testing, calibrating and process control instruments, namely, moisture meters, hygrometers not including household type hygrometers, humidity meters, stack gas analyzers, calorimeters, pressure gauges, level meters, temperature meters, dissolved oxygen meters, ph-meters, biochemical oxygen demand monitors, toxicity meters, sludge activity monitors in the nature of electronic devices used to track the respirometric, anaerobic, toxic, methanogenic, dissolved oxygen levels in sludge in fluids, titrators, electronic meters for measuring moisture balance and the loss of weight moisture, spectrophotometers for use in research laboratories, quality control laboratories and process control, spectrometers