User manual VAISALA HMW70U

[. . . ] All legally binding commitments and agreements are included exclusively in the applicable supply contract or Conditions of Sale. U304en-1. 1 HMW70U/Y Transmitters Operating Manual Contents 1. PRODUCT DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 TO BE NOTED WHEN MEASURING HUMIDITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 INSTALLATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] 10 GUARANTEE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2000-08-23 i HMW70U/Y Transmitters Operating Manual U304en-1. 1 This page intentionally left blank. ii 2000-08-23 U304en-1. 1 HMW70U/Y Transmitters Operating Manual 1. PRODUCT DESCRIPTION The HMW70 transmitters are wall mounted transmitters for the measurement of humidity (HMW70U) and for the measurement of humidity and temperature (HMW70Y). The HMW70U/Y transmitters can be mounted directly on the wall. One point calibration is easily performed with the HMI41 indicator and the calibration cable 19116ZZ. Both transmitter types incorporate the HUMICAP®180 humidity sensor which uses an operating principle based on changes in the capacitance of a thin polymer film as it absorbs water molecules. The HMW70Y transmitters measure temperature with the reliable Pt 1000 sensor. 2000-08-23 1 HMW70U/Y Transmitters Operating Manual U304en-1. 1 2. TO BE NOTED WHEN MEASURING HUMIDITY In the measurement of humidity and especially in calibration, it is essential that the temperature equilibrium is reached. Even a slight difference in the temperature between the measured object and the sensor causes an error. For example, at +20 °C (+ 68 °F) and 50 %RH, a temperature difference of +1 °C between the measured object and the sensor causes an error of +3 %RH. If relative humidity is 90 %RH, the error is about +5. 4 %RH. The error is at its greatest when the temperature of the sensor differs from that of the surroundings and the humidity is high. A few degrees' difference in temperature may cause water to condense on sensor surface. Efficient ventilation accelerates evaporation whereas in an unventilated space, it may take hours. The HUMICAP®180 sensor returns to its normal functioning as soon as water has evaporated. Any contaminated water condensing on the sensor may shorten its life span and change the calibration. 10 9 8 7 dRH (%RH) 6 5 4 3 2 1 0 -40 -20 0 20 40 60 80 100 Temperature (°C) Figure 2. 1 Measurement error at 100 %RH when the temperature difference between the ambient and the sensor is 1 °C 2 2000-08-23 U304en-1. 1 HMW70U/Y Transmitters Operating Manual 3. 3. 1 INSTALLATION Selecting the place of installation Select a place that gives a true picture of the environment or process and is as clean as possible. Air should circulate freely around the sensor. A rapid air flow is recommended as it ensures the same temperature for the ambient air and the sensor head. Install the transmitter in a place where no cold or hot spot can develop. If the sensor head is installed in a duct or channel where the temperature is different from the ambient temperature, insulate the point of entry. An uninsulated installation might lead to condensation on the sensor head and even if no condensation occurs, the resultant air flow may change the temperature near the sensor head and distort the readings. 3. 2 Mounting The HMW70U/Y transmitters can be mounted directly on the wall. First attach the base plate with the two screws provided. [. . . ] When an AC supply is used, an isolated source is recommended. DC 10. . . 35 V 14. . . 35 V 19. . . 35 V AC 9. . . 24 V 12. . . 24 V 16. . . 24 V 0. . . 1 V 0. . . 5 V 0. . . 10 V Factory setting 0. . . 1 V. Other outputs selectable by jumper connections. An output change causes an error which is less than 0. 5 %RH without recalibration. [. . . ]