Laboratory Exercise No.

2
Calibration of Platform Scale

OBJECTIVES:
1. To determine the level of accuracy of a platform scale in the
comparison to standard weights.
2. To know the proper use of the platform scale.

THEORY AND ANALYSIS:

Weights and forces are measured by comparison with known
weights with the aid of the system of levers such as in a beam
balance, or by reference to the amount they deform some elastic
object such as a spring, which has been previously calibrated
against standard weights.
Scales have been constructed to weigh a million pounds or
more, as in industrial plants, while the chemical balance, at the
opposite extreme, will easily weigh a millionth of a pound.
The common platform scales used in a laboratory. The
sensitiveness of a platform scale is determined by placing a large
weight on the platform, weighing it, and then finding the smallest
additional weight that will cause a deflection of the beam which can
be solely balanced by rider.
w nm
The relation of = is called the leverage, which is the ratio
W tL
of weight on the pan necessary to balance the weight of the
w
platform. Or simply, if the leverage ratio is , w kg is necessary to
W
balance W kg on the platform.
The graduations on the beam therefore must conform to the
relation between the weight of the pan and the beam together with
the poise.
By using standard weights and increasing the platform loads
by equal increments, the error may be determined for a given range
of loading. The error can be seen by comparing the reading of the
scale to the standard weight of the load.
This may also be done by pleasing the weights on different
locations of the platform scale, upon which the discrepancy in the
values obtained will reflect the accuracy of the platform scale.
APPARATUS:
1. Platform Scale
2. Weights specified by the Bureau of Standards

PROCEDURE:
1. Take the platform off and measure the length of all the lever
−1
arms between knife edges to the nearest of an inch. Draw
100
a simple line sketch showing all arms and lengths.
2. Observe the means provided to adjust the beam to read zero.
3. Carefully level the scale so that the platform is in a horizontal
plane. Be sure that there are no strong sources of ventilation
inside the testing room to produce erroneous readings.
4. With no weight on the platform, adjust the balance lever so
that the arm shall same be rest widely between the steps.
This balance may be secured by adjusting the weight of the
pan on the poise hook or by means of special adjustable
counter weight incorporated in the weighing mechanism.
5. Test the platform scale starting with a 10 kg weight. The
weight is first placed on the upper left corner of the platform
and the reading on the scale is recorded on the data sheet.
Obtain the readings with the weight placed on the lower left
corner, upper right corner, lower right corner and at the
center of the platform.
6. Repeat step 5 with increments of 5 kg.
7. Obtain the average of every load and calculate the
percentage of error.
8. Plot the calibration curve between the error of scale as
ordinates and weight in kg. as read from the scale beam as
abscissas, plus errors plotted above and minus errors below
the axis of abscissas.
9. Determine sensitiveness at no load, half load and full load
scale.
PLATFORM SCALE DATA SHEET
Platform Beam Readings, kg Error, Error,
Load, Corners Center Average kg Percent
kg. 1 2 3 4
5
10
20
Sensitiveness
Platform Load, kg Beam Load Increment Load Increment
Reading, to Lower Stop
Initial Center
Load
Zero
One-fourth Capacity
One-half Capacity
Three-fourth Capacity
Full Capacity

SAMPLE COMPUTATIONS:
In Table 1:

In Table 2:
CONCLUSIONS:
This laboratory focused on the calibration of the platform
balance. This lab has two objectives which are to determine the
level of accuracy of a platform scale. In the accuracy test
determining the platform scale and standard weights at the four
corners and the center should be the same, so the data we get from
the result are closer to the actual or original data, therefore, we are
doing it well.
Knowing the proper use of the platform scale is very
important, it is because an improper or inaccurate reading can
make a big effect on object’s weigh. The ways of using platform
balance are important, easy to do, and to make sure that the result
is accurate.

QUESTIONS:
1. How would the sensitiveness of a platform scale be
determined?

2. With the aid of the diagram, define the leverage ratio of the
platform scale used in the experiment.

3. If there are 454 grams in a 1-lb mass, what will this mass
weigh in grams, at an altitude where q = 20.6 ft/sec? What is
the mass in grams at the point?
4. If the platform balance is raised to an elevation of 5000 meters,
Will there be any change in the scale reading? Explain.
 EXPERIMENT NO.5
Calibration of Volume Tank

OBJECTIVE:
To calibrate the volume tank in reference to thoorition
procedures.

THEORY AND ANALYSIS:

Volume tanks range in size from those holding several
thousand gallons down to the chemists burettes and
graduates. Many types of gases and devices are used to
indicate the liquid level, such as floats, leakages, gage-glass
scales and hook gages.
The volume tank that holds relatively large volumes
generally consists of the tank itself, a side gage glass scale, a
weight scale and an outflow pipe. It also an inflow pipe of the
liquid located at the mouth of the tank.
Liquids under low pressures and even up to several
atmospheres are incompressible and possess a fixed density
as long as the temperature does not vary considerably. For
general purposes of calibration, liquid water is employed
because of its accessibility and known properties.
The weight of the water placed in the tank can be
measured theoretically by determining the volume and then
multiplying by the density of the water at room temperature.
The volume may be obtained by measuring the inner
dimensions of the tank, the longitudinal and latitudinal widths,
and the proposed height of the water. This weight is then
compared to the weight of the water in the tank: that is
obtained through actual weight measurements.
The reverse procedure may also be performed that is,
determining the weight of the water to be placed in the tank
by actual weighing and then comparing it with the theoretical
weight that its volume will occupy in the tank.

APPARATUS:
1. Volume Tank
2. Meter Stick
3. Thermometer
4. Platform balance

SET UP OF THE EXPERIMENT:

PROCEDURE:
1. Measure the longitudinal and latitudinal dimensions of
the tank.
2. Measure the weight of the volume tank (empty), with the
platform scale
3. Pour water into the tank until it reaches the maximum
level as indicated by the gage glass.
4. Measure the height of the water and determine the
volume
5. With the use of the platform scale, measure the weight of
the tank (total) and record by subtracting the weight of
 the empty tank to determine the actual weight of water.
The temperature of water each time.
6. Divide the maximus level by at least 10 equal
increments. For each increment, drain water through the
quick opening valve and repeat as in (5).
7. Prepare a calibration curve.
DATA SHEET:
Ru Experimental Standard Data Percentage
n Data Error
No. Heigh Computed Weigh Weigh Actual
t Volume t of t of weigh
(m3) water tank t of
(cm) and when water
tank empty (kg)
(kg) (kg)

SAMPLE COMPUTATION:
CONCLUSION:
 Laboratory Experiment 6
Measurement of Speed and Time

APPARATUS:
1. Variable speed motor
2. Stroboscope
3. Tachometer
4. Revolution counter and timer SET UP OF THE
EXPERIMENT:
SEP UP OF THE EXPERIMENT:
PROCEDURE:
1. Start the motor or generator that drives the shaft and
regulate the speed of the motor with the use of the
voltage regulator provided in the set-up.
2. Adjust the voltage to 10 percent of the input voltage.
Measure the speed with the use of the three different
methods of speed measuring devices such as
tachometer, stroboscope, and revolution counter.
3. Adjust the speed by increasing the voltage load by
increment of 10 percent and stop when the maximum
load is applied. Measure the angular speed of the shaft
at each increment.
4. Record all values on the data sheet.
5. Compare the values of the speed obtained with each
other and with their percentage ratings against the
input voltage.
6. Plot a curve for instruments reading against the
percentage of the input voltage.

DATA SHEET:
Run No. Distance Time Speed Revolution
(ft) (s) (ft/s) per Seconds
(RPS)
1
2
3
4
5
SAMPLE COMPUTATIONS:

CONCLUSION:

Laboratory Experiment No.7

Determination of Density, Specific Gravity and Viscosity of
Liquid Fuels

OBJECTIVES:
1) To determine the specific gravity of liquid fuels by means of
pycnometer and hydrometer method.
2) To be able to determine the viscosity of any liquid.

THEORY / HYPOTHESIS:
The specific gravity of a substance is defined as the ratio of
the weight of that substance to the weight of the water having equal
volume. This is merely a ratio or an abstract number. Actually, it is
quantitatively the same as density as in the case of metric system
since the standard unit, a cubic centimeter of water, weighs exactly
one gram. Specific gravity of a liquid is determined most accurately
in most cases where a sensitive chemist balance is available by the
use of a specific gravity bottle. The bottle is provided with a small
ground-glass stopper having a capillary tube or hole drilled through
it, so that when the bottle is filled to the top of capillary tube it will
always hold the same volume of liquid. In the determining the
specific gravity, the bottle is filled with the liquid to be tested with
care being taken to avoid the formation of air bubbles.
In commercial practice, the specific gravity of liquids is usually
determined by an instrument called a hydrometer. The hydrometer
is made usually of glass and consists of three parts:
(1) the upper part, a graduated stem or fine tube of uniform
diameter
(2) bulb, an enlargement of the tube containing air
(3) a small bulb at the bottom, containing shot of
(4) mercury which causes the instrument to float in a vertical
position.
 (5) The graduations are figures representing either specific
gravities or the numbers of arbitrary scale as Baume, API,
Twadell or Beck.

Fuels are all combustible substances obtained in bulb which may

be burned in atmospheric air in such a manner that the heat evolve
is capable of being automatically applied to domestic and industrial
uses for heating and the production of power. Fuels may be primary
(natural occurring) or secondary. Both categories include solid,
liquid, and gases. The different liquid fuels used in these
experiments in determining specific gravity are gasoline, diesel,
alcohol, oil for gasoline and diesel engine, and kerosene.
Commercial Falling-Sphere Viscometers are non-available. One type
of which is shown in the sketch. The one available is not of the
commercial type. This viscometer makes use of the principles in
case of flow around a small sphere.
Sample Data
Dynamic Assume
Liquid Density Specific Viscosity velocity
Fuels (kg/m^3) Gravity (Pa.s) m/s
Gasoline
Diesel
Engine
Kerosene
Alcohol
Oil for
Gasoline

Sample Computation:

Conclusion: