Beam balances

Wagbalken, m, balance beam, scale beam, wilgbar, a. weighable, ponderable,... 

If we return to our notched beam analogy, as shown in Figure 15-5, we find that we numbered the notches, 1, 2, 3, . These numbers serve as natural identifying designations. They are the quantum numbers of the balance beam. 

The standard modern instrument however is the electronic balance, which provides convenience in weighing coupled with much greater freedom from mechanical failure, and greatly reduced sensitivity to vibration. The operations of selecting and removing weights, smooth release of balance beam and pan... 

The determination of these curves requires not only the measurement of small amounts of heat in a microcalorimeter, but also the simultaneous determination of the corresponding quantity of adsorbed gas. Volumetric measurements are to be preferred to gravimetric measurements for these determinations because it would be very difficult indeed to ensure a good, and reproducible, thermal contact between a sample of adsorbent, hanging from a balance beam, and the inner cell of a heat-flow calorimeter. 

For the balanced beam-scrape adhesion test, ASTM-2197, weights were added to a commercial balanced beam tester. The kind of scratch produced by the stylus with the different loadings was recorded and served as a measure of film hardness. Coatings which are not scratched to bare metal by 500 g are desirable. 

Epoxy acrylate (Ebecryl 3700, 50%) combined with 25% TMPTA, 25% I BOA and with DIBF-OPPI-DIDMA pigment and FC-171 as above was also used to coat panels. These panels showed no removal of coating in the cross hatch adhesion test. With 6.8j there was no loosened coating on the frontal impact surface, and only 30% was loosened on the back surface. Five hundred grams were required to scratch to bare metal with the balanced beam. Performance was... 

Fig. 2. A method of measuring the contractile force in a hot filament 1. This force is equilibrated by the weight 4 which can be rolled along the balance beam 3. The filament is attached also to base 2...

Figure 6. Multivariate factor analysis of beef showing the " distribution" of experimental treatments, volatile chemical attributes, chemical protein elements and flavor attributes in beef samples during postmortem aging. Insert represents the data redrawn with the graphical origin depicted as the fulcrum of a balance beam.

Figure 2-4 Single-pan mechanical balance. To weigh an object on the pan, we use mechanical knobs to detach removable weights until the balance beam is restored as near as possible to its original position. The remaining small deflection is read on the optical scale.

All devices are susceptible to power quality no devices are 100% immune. All electrical power system installations have power quality anomalies to some degree, and no power systems exist for which power quality problems are nonexistent. The challenge, therefore, is to create a balance. In Figure 1.21, the balanced beam represents the electrical power system. Power quality and equipment immunity are two forces working in opposition. The object is then to a create a balance between the two. We can assign power quality indices to the various locations in the power system and immunity indices to the loads. By matching the immunity index of a... 

Pelouze Scale Company (Pelouze R-47 photographic balance beam, postage scales), Sanford, 2707 Butterfield Road, Oak Brook, Illinois 60523 t (877) 724-8324 www.pelouze.com. 

Significant temperature gradients in the furnace chamber will cause gaseous flow from hot to cold, which may apply a spurious force to the specimen pan. This is a more severe effect for chambers under moderate vacuum ( thermomolecular flow [3]). Purge gas flow direction may be an important consideration, in order to avoid condensation of gaseous products on the hangdown wire, or along the balance beam, as the gas flows out of the hot zone of the furnace. 

The mechanical aspect of these balances typically employs a crankshaft or rocker arm assembly that supports the weights. The weights are engaged or disengaged on the balance beam as the shaft is turned. Typically, only four weights per... 

Free-floating balloons of thin glass and rubber were first tried. The glass was too heavy the rubber too permeable. Balloons suspended from springs were too insensitive, and balloons suspended from balance beams were too mobile. A gas density balance operated by the pull of a large solenoid or an enclosed magnet was used but, although extremely sensitive, it was discarded because it involved an unnecessary and somewhat erratic variable. 

Since the measurements may be carried out over a period of several hours to several days, it is essential to design the balance and its supports so that the effect of any thermal change will be minimized. The important factors involved are (1) the relative length of the two halves of the balance beam, (2) the torsional resistance of the supporting wire, (3) the relative position of the beam to the supporting frame, and (4) torsional resistance of the end-supporting wires. 

Fused reworked quartz is chosen as the material for the beam since it has the lowest coefficient of expansion of any material. The value of the coefficient is 0.0042 X 10 4 cm./cm./°C. If the temperature variation over the two halves of the beam is 1°C. the difference in length of the two halves will be four parts in ten million. Since a difference of temperature of 1°C. over the beam length is not to be expected in a thermally shielded system, changes in length of the balance beam can be made negligible. 

To observe accurately the position of the beam, a scale micrometer microscope is used. In order to determine the rest point of the balance, the micrometer screw is adjusted until the balance beam is deflecting equally about a fixed point on the scale. Reading the amplitudes is necessary where measurements are carried out in high vacuum (less than 10-5 mm. Hg). For measurements involving an appreciable gas concentration, the system is damped and the beam assumes a stable position within a few minutes. Here the pointer is followed directly on the micrometer screw. 

For each experiment the weighed metal specimen is placed on the balance beam and checked for position and alignment. The balance tube is now sealed off and the apparatus evacuated to a pressure of 10-B mm. of Hg or better. Liquid nitrogen is placed in the traps during the process. 

If an oxidation rate experiment is to be made, the furnace, set to the desired temperature, is raised around the specimen tube. After thermal equilibrium is attained, a preliminary set of readings of the balance beam and furnace temperature is taken. A measured quantity of oxygen is then admitted, establishing in the reaction vessel the desired pressure. Readings of the balance beam are taken at fixed intervals during the oxidation. At the end of the experiment the system is evacuated and a final set of readings is taken. 

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