ASTM E Standard Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures). Find the most up-to-date version of ASTM E at Engineering ASTM-Epdf – Download as PDF File .pdf), Text File .txt) or read online.
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The external thermocouple is also attached to the substrate using a magnet to get a good thermal contact for the surface temperature measurement.
Historical Version s – view previous versions of standard.
No items in cart. This is shown daily in the layer of moisture e373 collects on a cold windowpane in the presence of boiling water or, more interestingly, on the outside of a glass of cold beer. This standard is also available to be included in Standards Subscriptions.
In this case, the instrument comprises a wet-bulb thermometer only. The surface temperature is measured either using an integrated K-type thermocouple sensor mounted next to the RH and Air Temperature sensors or by using an optional external thermocouple sensor connected via a K-Type connector. The method for determining the Relative Humidity and hence the Dewpoint Temperature that has been most commonly taught to Paint Inspectors is the Wet and Dry Bulb method, commonly called the Whirling or Sling Hygrometer.
It is therefore essential that the relative humidity RHthe air temperature Ta and the surface temperature Ts are measured quickly and accurately so that the dewpoint temperature Td and the difference between the surface and dewpoint temperatures can be calculated for correct paint or not paint decisions to be made. Link ast Active This link will always route to the current Active version of the standard. However, the hygrometers described in this method use mercury in glass thermometers, which are no longer acceptable under Restriction of Hazardous Substances RoHS legislation round the world.
Measurement of relative humidity in controlled conditions is not practical for the whirling or sling hygrometer as the presence of an operator in the controlled environment causes errors.
The traditional method of evaluating the climatic conditions for painting has significant limitations in e373 due to the time taken to obtain readings and the potential errors of these readings.
When an external thermocouple sensor is connected the integrated surface temperature sensor is disconnected from the gauge. The reference values are set using the controls for the chamber and measured independently using calibrated equipment.
Even when an Electronic Dewmeter astmm taken from a warm office or car to a cold environment, an accurate reading of rh can be obtained in less than 30 seconds. The values quoted in table 1 are obtained from the calibration software and can e37 shown to a resolution of two decimal places.
The advantages of the Electronic Dewpoint Meter are in the speed and accuracy of the measurement and in the traceability of the gauge calibration e37 a national standard. Figure 5 — Dewpoint Meter Configured for Data-Logging Data can be recorded using two methods, user activated recording of values as and when required or the data-logging mode, with reading sets recorded automatically at the end of the pre-set interval.
This is also true for whirling and sling hygrometers as when these encounter immovable objects such as pillars the tendency is to break the spirit-in-glass thermometers. Note — Ta will be the same value as Tdb. Each set of readings consists of an RH value, the corresponding air temperature, surface temperature and the calculated Dewpoint Temperature and temperature difference, together with the estimated values for wet bulb and dry bulb temperatures.
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ASTM E337 – 15
The definition of the Dewpoint Temperature is the temperature at which moisture will satm from a body of air at a higher temperature. The E37 gauge displays the parameters to one decimal place. No other units of measurement adtm included in this standard. Content only available by subscription. The air temperature is measured using another semiconductor sensor mounted close to the RH sensor to minimize any differences in conditions.
In the datalogging mode the gauge is attached to the steel substrate by three strong magnets mounted in the back of the gauge case. These temperatures make allowance for the accuracy of the measurement of relative humidity and surface temperature in the field and also deal with any inertia in the evaporation from a surface as it warms up.
As the voice of the U. Enter your personal account email address to request a password reset: Only the essential features of the psychrometer are specified.
Data stored in the memory of the Dewpoint Meter can be transferred to a computer operating data management software. Please first log in with a verified email before subscribing to alerts. The estimated values for the wet bulb temperature Twb and the dry bulb temperature Tdb can be displayed by selecting these parameters from the Display menu in preference to two of the usual set, e. The feature in the electronic Dewmeter that displays the calculated wet bulb temperature and the measured dry bulb temperature the air temperature, Ta has good agreement with the wet and dry bulb method in conditions of stable relative humidity.
These errors accumulate from a number of operational issues such as alignment of the lens in the glass thermometers for optimum position when reading both thermometers, parallax errors when reading the position of the thread relative to the scale on the glass, heat from hands transmitted to the bulbs of the thermometers and resolution of the measurement and the conversion of the readings to rh and dewpoint.
Data can be recorded using two methods, user activated recording of values as and when required or the data-logging mode, with reading sets recorded automatically at the end of the pre-set interval.
Figure 3 — Digital Electronic Dewpoint Meter It can clearly be e337 that if a surface is cooled sufficiently the surrounding air will eventually give up its moisture to the cool surface.
You currently cannot view this content. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to aztm. ASTM grants you a astn as follows: The method specified is based on measuring air temperature and relative humidity, calculating the dewpoint temperature, measuring the steel surface temperature, and estimating the minimum surface temperature above the dewpoint temperature that is needed to avoid condensation under the prevailing environmental conditions.
Examples of these measurement devices are shown in figures 1 and 2 below.
Recent Developments in the Measurement and Monitoring of Climatic Conditions
There are several operational aspects of the wet r337 dry bulb hygrometer method for measuring humidity that influence the accuracy of the measurement including insufficient whirling so steady-state conditions are not reached, contamination of the water so optimum evaporation conditions for the wet bulb are not achieved, the use of spirit-in-glass thermometer in place of the environmentally unsound mercury-in-glass thermometers.
Similarly the data-logging option can be chosen when a new batch is selected by pressing the clock softkey. The memory capacity is a maximum of 25, records or sets, in up to different asfm.
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A semiconductor sensor is used to measure the relative humidity so the measurement response time is much quicker than the traditional wet and dry bulb method that can take 20 minutes or more to reach steady-state conditions, at which point the temperatures of the bulbs can be read.
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