I've an interest to construct a rheometer. But, only have an inkling on it. I got this idea when I heard about a fest that is going to take place soon, in one of the top-most engineering colleges at my place. However, I can't make it, as there's no time.Actually, another interesting idea crossed my fickle mind, however, I'd finally resolved to do the former-rheometer.And I felt that it's worth including some posts in my blog based on some measuring instruments.
Firstly, a measuring instrument has three functional elements, namely:
- a primary element to detect changes in the magnitude of the variable,and
- a transmitting means for connecting the detecting element to
- measuring element
Most industrial products are manufactured to meet certain specified physical and chemical properties. And, I'm herewith different measuring devices that are employed for different process variables.I would post them in series.In this post, I'm going to discuss hydrostatic balance, specific gravity bottle, or pycnometer and hydrometer, which are used to detect the specific gravities of solids and liquids. Note: I could even modify/append/delete any content in my posts whenever I feel it as necessary.
1.Let us start with
hydrostatic balance- It is a balance adapted for weighing a body in air and in a liquid. To determine the specific gravity of an insoluble solid heavier than water, the sample is first weighed in air, and then in water. Let mass of the sample in air = m1 and
mass of sample in water = m2
Then, (m1-m2) is the mass of an equal volume of water. The specific gravity of the sample is, then,
s = m1/(m1-m2) at the temperature of the experiment, t degree C.
True specific gravity = s* (sp.gr. of water at t deg. C)
To determine the specific gravity of a solid which is soluble in water but heavier, the sample is first weighed in air and then in a liquid in which it doesn't dissolve.
Let mass of sample in air = m1
mass of sample in the liquid = m2
Specific gravity of the liquid relative to water = s'
The specific gravity of the solid relative to water is s = [m1/(m1-m2)] s'
To determine the specific gravity of an insoluble solid, which is lighter than water, the sample is first weighed in air. The sample is tied to a sinker and the sample is weighed in air with the sinker dipped in water and then, the weight of the sample and sinker both in water is determined.
Let mass of the sample in air = m1
Mass of the sample in air and sinker in water = m2
Mass of the sample and sinker in water = m3
The specific gravity of the sample is s = m1/(m2-m3)
2.
Pycnometer or
Specific Gravity Bottle- It is a flat bottomed bulb-like glass bottle with a long, tapering neck. A well-ground solid glass stopper with a narrow bore fits the neck. If the bulb is filled with a liquid and the stopper dropped in place, some liquid comes out through the bore and the bottle contains a fixed volume of the liquid.
To determine the specific gravity of a liquid, clean, dry, empty bottle with stopper in place is weighed. The bottle is then filled with liquid and weighed. It is then washed clean, filled with water, and weighed. Let mass of the empty bottle be m1.
Mass of bottle filled with the liquid = m2
Mass of the bottle filled with water = m3
The specific gravity of the liquid is s = (m2-m1)/(m3-m1)
To determine the specific gravity of a granular solid, which is insoluble in water, the empty bottle is first weighed. About one-third of the bottle is then filled with the granular solid and weighed. The rest of he bottle is filled with water, taking care that no air bubble is entrapped, and the bottle is weighed again. Finally, the bottle is washed clean, filled with water and weighed. Let the mass of dry, empty bottle be m1.
Mass of bottle partly filled with granuled = m2
Mass of bottle + granules + water = m3
Mass of bottle filled with water = m4
The specific gravity of the granular solid is calculated as follows: s= m2-m1/(m4-m1)-(m3-m2)
To determine the specific gravity of a granular solid, which is soluble in water, select a liquid of known specific gravity s', in which the solid is insoluble. Repeat the step as mentioned above with the liquid insted of water. The specific gravity of the granules relative to the liquid is s1 = m2-m1/(m4-m1)-(m3-m2)
and that relative to water : s=s1 * s'
3.Hydrometer: This consists of a weighed float with a stem of small diameter proportioned so that the height of the scale submerged in the liquid in which it is floated varies according to the density or specific gravity of the liquid. Since the weight of the hydrometer is constant, it measures directly the volume of the liquid which is equal to the weight of the hydrometer. It is calibrated in terms of density or specific gravity.
I may take some time to post on rheometer. And for your kind information, I may refer some books, or gather sufficient information from library, and even inquire as many professionals as possible before posting here on certain topics.
------->(1)ΔQ = heat input or heat lost, Jh = heat transfer coefficient, W/(m2K)A = heat transfer surface area, m2ΔT = difference in temperature between the solid surface and surrounding fluid area, KΔt = time period, sThe overall heat transfer coefficient U is a measure of the overall ability of a series of conductive and convective barriers to transfer heat applied to heat exchangers. 
R = Resistance(s) to heat flow in pipe wall (K/W)But more complex relationships exist, for example when heat transfer takes place by different routes in parallel.And the thermal resistance due to the pipe wall is calculated as follows-
x = the wall thickness (m)k = the thermal conductivity of the material (W/(m·K))A = the total area of the heat exchanger (m2) The following relationship is often used: 
= 
Upre = overall heat transfer coefficient based on calculated or measured ("clean heat exchanger") data, 
