E77 – 98 Standard Test Method for Inspection and Verification of Thermometers, Calibration-temperature instrumentation, Liquid-in-glass thermometers. Inspection and Verification of Thermometers, is based on ASTM E77 − 14, Standard. Test Method . E1 Specification for ASTM Liquid-in-Glass Thermometers. Buy ASTM E() Standard Test Method for Inspection and Verification of Thermometers from SAI Global.
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This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because it may not be technically possible to adequately depict all changes accurately, ASTM recommends that atm consult prior editions as appropriate. In all cases only the current version of the standard as published by ASTM is to be considered the official document.
A number in parentheses indicates the year of last reapproval. A superscript epsilon indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. Current edition approved Nov. Originally published as E 77 — 49 T. Last previous edition approved in as E 77 — It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Some that are considered essential to this standard are given below. If the pigment in the scale etchings washes out or fades, the thermometer will be difficult to read. Improper annealing of the bulb, as determined by the bulb stability test, will result in thermometer readings rapidly changing with time and use. The thickness of such gages should approximate the diameters of the holes to minimize errors resulting from the axis of the thermometer stem being other than normal to the plane of the gage.
Suitable types are described in Appendix X1. Metal block baths and the salt and tin comparator baths, described in Appendix X1, are examples of the type of equipment that has been found to be suitable for this purpose. Temperatures are not measured directly with this instrument. Its electrical resistance is determined by comparison with a standard resistor, using a potentiometer, a Kelvin-type double bridge, or a Wheatstone bridge, preferably of the Mueller type or an AC resistance bridge.
Temperatures may then be calculated using suitable resistance- temperature equations. In order that it shall be satisfactory for such use, the thermometer should meet the requirement that the ratio of resistances at the steam and ice points shall be greater than 1. More complete information on the construction and use of primary standard thermometers may be obtained from NIST SP They are simpler to use than a primary standard thermometer with its accessory equipment, the latter being capable of an order of precision and accuracy far in excess of that attainable with liquid-in-glass thermometers.
The choice of a secondary standard will be governed by various factors. Scale corrections should always be applied in the use of these standards. Secondary standards may be of the following types. They should be completely recalibrated every 6 to 12 months, depending upon the temperatures of usage. Ice points should be taken every 3 months. Total-Immersion Thermometers—In the case of general purpose total-immersion thermometers, the sensitivity of the thermometers to be tested will govern the choice of standard.
For fractionally graduated thermometers a calibrated set of the following thermometers is recommended. The change in ice-point reading should then be applied to all readings. It is only necessary to have a liquid-in-glass thermometer completely calibrated one time.
Recalibration is performed as described in 6. These thermometers can be used as standards to calibrate other thermometers similar in all details of construction above the immersion point, but may differ below the immersion point to the extent of including an auxiliary ice point scale.
No method has been discovered that will entirely prevent such displacement of the gas. If bubbles are observed in the bulb, they can generally be removed by cooling the bulb with dry ice or other convenient coolant until all the liquid is s77 into the bulb.
Gentle tapping of the thermometer while held upright w77 cause the bubbles to rise to the surface. If a mercury separation is observed in the stem, several different ways are suggested for joining aztm columns, depending on the construction of the thermometer and the type of separation.
If a small portion of the liquid has separated at the top of the column and the thermometer is provided with an expansion chamber, r77 liquid usually can be joined by carefully and slowly heating the bulb until the separated portion is driven into the expansion chamber. When the column itself follows into the chamber, the separated portion usually will join onto the main column.
A slight tapping of the 4 E 77 — 98 thermometer against asm palm of the hand will facilitate this joining.
Thermometers that have a contraction chamber below the lowest graduation are likely to develop separations either in the chamber or above it. It is frequently possible to join such separations by cooling the thermometer so that the separated portion as well as the main column both stand in the chamber. Tapping the tube against the hand or the bulb on a soft spongy material, such as a rubber stopper, aastm will bring the liquid together.
Astmm more stubborn separations it may be necessary to cool the bulb in dry ice to a point low enough to bring all of the liquid into the bulb itself. By softly tapping on a soft spongy material or against the hand it usually is possible to bring the liquid together in the bulb. The bulb should be allowed to warm up slowly. The liquid should emerge into the bore with no separation.
ASTM E77 – 98 Standard Test Method for Inspection and Verification of Thermometers
Such thermometers should always be inspected for these separations, which can be repaired by the procedures described above. Organic liquids as used in thermometers, in contrast to mercury, wet the glass. It is frequently a good practice to immerse only the bulb of the thermometer. This keeps the viscosity of the liquid in the capillary low and aids in hastening drainage. If such globules appear to unite and then reappear on cooling the bulb, they are indicative of oxidation of the mercury or the presence of obstructions in the bore, and should result in rejection of the thermometer.
The most common types of foreign matter which should be cause for rejection are glass chips, particles of dirt or lint, oxide of mercury either red, yellow, or blackproducts of glass weathering commonly called white deposit, and stones or iron spots traceable to faulty glass fabrication. Under these conditions oxidation of the mercury will occur and will normally be evidenced by the production of crystals of red oxide of mercury after 10 to 12 h of exposure.
ASTM E77 – 14e1
Any stones or striae that distort the bore or its appearance should be cause for rejection. Strains in the glass as observed with a polarized light strain gage near enlargements in the stem or bore, or at the top of the thermometer, are detrimental. In the case of diameter measurements, the bulb or other portions of the thermometer being tested should not enter the smaller of the holes in the ring gage see 5. In the case of ASTM thermometers, the diameter limits apply over the entire length of the section of the thermometer being tested.
Normally, the effect of taper in the capillary or nonlinearity in the expansion characteristics of organic liquids is manifested by a gradual change in the spacing of the graduations.
Discontinuities in the spacing are evidence of faulty graduating. Inspection for uniformity of spacing can generally be accomplished by eye, but for greater accuracy a pair of dividers may be used to advantage. Adjust the dividers to extend over 10 or 20 graduations, and successive intervals can be intercompared rapidly. Allow to cool slowly. Inspect the thermometer for differences in appearance of the tested and untested sections of the scale portion.
Burning out, loosening, chalking, or fading of the pigment shall be cause for rejection. If natural cooling in still air is used, determine the reference reading within 1 h. Return the thermometer to the bath, preheated to the temperature of test, and heat for 24 h.
Allow the thermometer to cool, at the same rate as at the start of the test, to the temperature referred to above, and redetermine the reference reading under the same conditions as before. The magnitude of any change in this reference reading as a result of the h heating period is a measure of the quality of the bulb glass and the adequacy of the previous heat treatment accorded the thermometer in manufacture.
Heat the thermometer to the selected reference point on the main scale, maintain the temperature for at least 15 min, and determine the scale correction at this point. If natural cooling is used, the correction should be determined within 1 h. Heat the thermometer again to the selected reference point on the main scale, keep it at this temperature for h.
Allow the thermometer to cool as described in and then repeat the procedures described in and. It must be emphasized that to obtain meaningful results, the procedure adopted after the h period of heating must be identical to that used in the original calibration. In reading thermometers, account must be taken of the fact that the lines are of appreciable width.
If any portion of the stem containing mercury is exposed, the emergent mercury column correction should be determined. In some instances total-immersion thermometers may be used under conditions of complete immersion. This is due to the effect of increased gas pressure above the column producing a distortion of the bulb. Select clear pieces of ice or ice made from distilled or pure water.
Discard any cloudy or unsound portions. Rinse the ice with distilled water and shave or crush into small pieces, avoiding direct contact with the hands or any chemically unclean objects. As the ice melts it will be necessary to drain off some of the water and add more crushed ice. Successive readings taken a.