外文翻譯----數(shù)字溫濕度傳感器(sht1xsht7x)(編輯修改稿)
2025-02-14 00:00 本頁(yè)面
【文章內(nèi)容簡(jiǎn)介】 y Sensor RH/Temperature pensationFor temperatures significantly different from 25 176。C (~77 176。F) the temperature coefficient of the RH sensor should be considered:RHtrue = (T176。C 25)?(t1 +t2 ?SORH)+RHlinear TemperatureThe bandgap PTAT (Proportional To Absolute Temperature) temperature sensor is very linear by design. Use the following formula to convert from digital readout totemperature:Temperatur e = d1 +d2 ?SOTTable 8 Temperature conversion coefficientsFor improved accuracies in extreme temperatures with more putation intense conversion formulas see application note “RH and Temperature NonLinearity Compensation DewpointSince humidity and temperature are both measured on the same monolithic chip, the SHTxx allows superb dewpoint measurements. See application note “Dewpoint calculation” for more.4 Applications Information Operating and Storage ConditionsFigure 11 Remended operating conditionsConditions outside the remended range may temporarily offset the RH signal up to 177。3 %RH. After return to normal conditions it will slowly return towards calibration state by itself. See “Reconditioning Procedure” to accelerate this process. Prolonged exposure to extreme conditions may accelerate ageing. Exposure to ChemicalsChemical vapors may interfere with the polymer layers used for capacitive humidity sensors. The diffusion of chemicals into the polymer may cause a shift in both offset and sensitivity. In a clean environment the contaminants will slowly outgas. The reconditioning procedure described below will accelerate this process. High levels of pollutants may cause permanent damage to the sensing polymer. Reconditioning ProcedureThe following reconditioning procedure will bring the sensor back to calibration state after exposure to extreme conditions or chemical vapors. 8090 176。C (176194176。F) at 5 %RH for 24h (baking) followed by 2030 176。C (7090176。F) at 74 %RH for 48h (rehydration) Temperature EffectsThe relative humidity of a gas strongly depends on its temperature. It is therefore essential to keep humidity sensors at the same temperature as the air of which therelative humidity is to be measured.If the SHTxx shares a PCB with electronic ponents that give off heat it should be mounted far away and below the heat source and the housing must remain well ventilated. To reduce heat conduction copper layers between the SHT1x and the rest of the PCB should be minimized and aslit may be milled in between (see figure 13). MembranesA membrane may be used to prevent dirt from entering the housing and to protect the sensor. It will also reduce peak concentrations of chemical vapors. For optimal response times air volume behind the membrane must be kept to a minimum. For the SHT1x package Sensirion remends the SF1 filter cap for optimal IP67 protection. LightThe SHTxx is not light sensitive. Prolonged direct exposure to sunshine or strong UV radiation may age the housing. Materials Used for Sealing / MountingMany materials absorb humidity and will act as a buffer, increasing response times and hysteresis. Materials in the vicinity of the sensor must therefore be carefully chosen.Remended materials are: All Metals, LCP, POM (Delrin), PTFE (Teflon), PE, PEEK, PP, PB, PPS, PSU, PVDF, PVF For sealing and gluing (use sparingly): High filled epoxy for electronic packaging (. glob top, underfill), and Silicone. Outgassing of these materials may also contaminate the SHTxx (cf. ). Store well ventilated after manufacturing or bake at 50176。C for 24h to outgas contaminants before packing. Wiring Considerations and Signal IntegrityCarrying the SCK and DATA signal parallel and in close proximity
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