Description The HU-226 is an extremely fast, stable and accurate temperature/humidity transducer designed for harsh environments. The polymer humidity capacitance sensor is not affected by harsh contaminants, condensation, fog or extremely high humidity over a prolonged period of time. If dust or other contaminants accumulate on the sensor, the probe can be washed in industrial grade isopropyl alcohol and put back in service without any calibration shift. Each unit is individually calibrated in an environmental test chamber to meet or exceed NIST traceable ± 2% or ± 3% accuracies. The HU-226 is temperature compensated for -30°F to +130°F operation with negligible error. Field selectable outputs, and fully temperature-compensated NIST traceable accuracy, non-interacting zero and span adjustments, NEMA-4 (IP-65) steel enclosure with external mounting bracket, short circuit and reverse polarity protected output, and a liberal two year warranty are some of the features which make the HU-226 the industry's highest performance, most reliable temperature/humidity transducer. The HU-226 incorporates a bulk polymer capacitive humidity sensor and precision NTC thermistor/platinum RTD temperature sensor. Both temperature and humidity sensors are immune to most contaminants and at the same time provide a stable, repeatable, accurate humidity and temperature measurement with negligible hysteresis. The sensing elements are not affected by condensation. In fact, the probe may be immersed in distilled water without degrading the calibration accuracy. The HU-226 utilizes sophisticated integrated circuits to provide a high level, fully conditioned, and temperature-compensated humidity output. The thermistor temperature sensors are available with more than ten different industry standard resistance to temperature curves offering compatibility to most if not all control systems. All thermistor sensors offer ±0.2°C interchangeability/accuracy. All thermistors strictly conform to industry standard R/T curves. The platinum RTDs are available with 100 ohm or 1000 ohm DIN 437630 standards with glass beaker ± 0.12% accuracy at 0°C. All temperature sensors have more than 3.0 mW/°C heat dissipation constant. On VDC output units (humidity only), two additional field selectable options are available: dual outputs 0 to 5 or 0 to 10 VDC, and dual unregulated supply voltages 12 to 35 VAC or 12 to 40 VDC. By merely moving a shorting plug, one can select the desired output for the specific application. As far as supply voltage is concerned, the unit automatically configures for AC or DC and no field selection is necessary. Another feature is that the output is fully protected from short circuit to ground, or if the supply voltage is applied by mistake to the output. Past experience demonstrates that field related wiring problems do occur. Instead of denying this fact, this protection circuit is designed in to ensure trouble-free start-up. The VDC output unit is also designed to handle low impedance circuits. In fact, the unit can drive up to 1K ohm minimum. In this way, multiple controllers, indicators, or other devices can be paralleled to the output without performance degradation. The mA output units (humidity only) function over a wide unregulated supply voltage range: 12 to 40 VDC without any affect on calibration or performance. The unit has reverse polarity protection built in. As a result, it is next to impossible to damage the unit by wiring incorrectly. By using sophisticated low dropout voltage regulators and CMOS integrated circuits, the mA output unit can drive very high output impedance. In fact, with only 12 VDC supply, the unit can drive 400 ohms. At 40 VDC, the unit is capable of handling up to a 3000 ohm load. In this way, the output loop can be tied in series to multiple controllers, indicators, and other devices without degrading the performance. NIST traceable humidity standards are utilized to calibrate and certify the HU-226. Calibration data on each unit is archived digitally for SPC and QC purposes. All automated calibration systems are networked and data is available online to numerous individuals at the same time. In this way, extremely high standards of quality and calibration integrity are maintained. The HU-226 incorporates a rugged NEMA-4 (IP-65) fully gasketed, dustproof, and splashproof enclosure. The enclosure has an external mounting bracket to facilitate field installation. A ½'' (.875'' /22.25 mm diameter) knock-out for conduit connection is also provided. A liquid tight cable connector is supplied if the unit is not being hard wired. Once installed, the enclosure maintains its environmental rating and protects the electronics and the sensing element from condensation, corrosive contaminants and other environmental pollutants. The enclosure also has additional features for ease of installation including unpluggable terminal block, easily accessible zero and span trimmers, and conveniently located shorting plugs for field selection.