COURSE UNIT

BACHELOR OF SCIENCE IN MECHANICAL

ENGINEERING: MECHANICAL ENGINEERING
LABORATORY 1

COURSE MODULE COURSE UNIT WEEK

13 13
Calibration of Platform Scale

CHECKLIST
 Read course and unit objectives
 Read study guide prior to class attendance
 Read required learning resources; refer to unit
terminologies for jargons
 Proactively participate in classroom discussions
 Participate in weekly discussion board (MS Teams)
 Answer and submit course unit tasks

UNIT EXPECTED OUTCOMES (UEOs)

At the end of this unit, the students are expected to:

Cognitive:
1. Use measuring instruments in the performance of laboratory exercises.
2. Analyze the significance of the quantities determined using engineering measuring devices.
3. Analyze the properties of fuels and lubricants using different methods.
4. Design an experiment involving measurement of properties.

Prepared by: Engr. Sandra E. Abancio, RMEE

Affective:
1. Listen attentively during class discussions
2. Demonstrate tact and respect when challenging other people’s opinions and
ideas
3. Accept comments and reactions of classmates on one’s opinions openly and
graciously.

Psychomotor:
1. Participate actively during class discussions and group activities.
2. Express opinion and thoughts in front of the class.

STUDY GUIDE

Standard Procedure for Calibration and Maintenance of Weigh Balances

 ISO = International Organization for Standardization

 Tolerance for weigh balances = Acceptable limits or range in measurement (in grams) that
the laboratory can tolerate

Instrument Calibration

1. Weigh balances are inspected, cleaned and calibrated annually by ISO 17025 accredited
vendor

2. Perform accuracy check of weigh balances once per year, approximately six months after
vendor calibration

3. Calibration of the reference weights is performed every two years by an ISO 17025
accredited vendor. Weights may be calibrated more frequently if deemed necessary (e.g.
weight is dropped, chipped, etc.)

Sample Handling and Storage

1. Wear clean cotton gloves (supplied with reference weights) or use forceps while handling
reference weights. To avoid depositing oil and dirt onto the surface of the weight, do not
touch weights with bare hands.

Prepared by: Engr. Sandra E. Abancio, RMEE

 2. Store reference weights in cases provided by the manufacturer.

Quality Control

 For quality control purposes, the required information is documented on the appropriate
form(s)

Interferences

1. For optimal performance, place balance on a stable, even horizontal surface with minimal
vibration. Avoid areas with excessive heat and moisture, direct sunlight, aggressive
chemical vapors and drafts.

2. If a balance is transferred to a different location, perform the accuracy check prior to use in
the new location

Non-Conforming Data

1. When verifying the calibration of weight balances, confirm any discrepancies in weight
measurements by repeating the operation. Notify a service representative, if necessary, to
re-calibrate the instrument when the calibration check shows that the weigh balance is
outside of the acceptable tolerance range
2. Replace the equipment if the vendor determines that a weigh balance or reference weight is
out of tolerance and cannot be properly calibrated

3. Procedures will be consistent with SOP ADM-07, Non-conformance reports

Data Management

 Electronically maintain an inventory of weigh balances and reference weights requiring

vendor calibration (see section 14). After each addition to or deletion from the inventory, file
a hard copy of the inventory in the Weigh Balance Calibration Record book.

 Data will be archived consistent with SOP ADM-03, Records and Archives

Prepared by: Engr. Sandra E. Abancio, RMEE

Cautions

1. Remove reference weights from service when the calibration expires (two years from the date of
calibration). Return weights to service when recalibration is completed.
2. Perform annual calibration of weigh balances at approximately the same time each year.

3. See section 5 for guidance on proper handling of reference weights.

Special Apparatus and Materials

1. Weigh Balances. Used to measure the weight of objects in the laboratory, such as media
and reagent ingredients and disinfectant containers.

2. Reference weight set (range of 1g to 50g) and Individual reference weights (1mg, 10mg,
100mg, 100g, 500g, 1 kg, 2 kg). Used as reference standards to verify the calibration of the
weigh balances.

Procedure and Analysis

 Calibration certificates must contain the stamp of the accrediting body (e.g. A2LA, NVLAP)
and the calibration vendor certificate number.

Calibration of Weights

a. When the calibration of a weight or weigh set expires (two years from the date of
calibration), remove it from service.

b. Consult ISO 17025 accredited vendor regarding quote for service, packing/shipping
instructions, and completion of any required forms prior to shipping weights.

c. Pack and ship weights to vendor.

d. Once the weight or weight set has been recalibrated and shipped back to the laboratory, file
the calibration certificate in the Weigh Balance Calibration Record book and return the
weights to service.

Prepared by: Engr. Sandra E. Abancio, RMEE

Daily Calibration and Use of Weigh Balances

a. Follow the instructions provided by the manufacturer for the operation of each weigh
balance. See section 15.

b. Each balance has a built-in calibration system.

c. When weighing, apply load to center of balance. Close balance doors, if applicable, to
reduce draft.

d. Clean balance pan after each use with a soft brush or damp towel. Allow the balance to dry
before the next use.

Six Month Accuracy Check of Weigh Balances

a. Perform accuracy check of weigh balances once a year, approximately six months after
vendor calibration, using reference weights.

b. See the Reference Weight Selection for Sixth Month Accuracy Check (section 14) for
guidance on which reference weights to use to verify the calibration of each weigh balance.

c. See section 5 for guidance on handling reference weights.

d. Tare or “zero” the weigh balance before the addition of each weight.

e. Add weights to center of balance and close balance doors, if applicable.

f. Record results for each reference weight on the Verification of Weigh Balance Calibration
Record Form (section 14).

g. See section 12.4 for acceptable tolerances for weigh balances when conducting the
accuracy check.

Prepared by: Engr. Sandra E. Abancio, RMEE

 h. Note that the acceptable tolerance varies for the 10 and 100 mg reference weights,
depending upon whether they are being weighed on a top loading balance that reads to
0.01g or a more sensitive analytical balance.

Six Month Accuracy Check of Weigh Balances – Acceptable Tolerances

Annual Calibration of Weigh Balances

a. Contact ISO 17025 accredited vendor and schedule a date for calibration.

b. Weigh balances are not shipped out. The vendor inspects, cleans, and calibrates balances
on site.

c. File the calibration certificate in the Weigh Balance Calibration Record book.

Prepared by: Engr. Sandra E. Abancio, RMEE

REFERENCES

1. Power Plant Testing By Moyer

2. Figliola, R.S. & Beasley, D.E., Theory & Design for Mechanical Measurements, 5th edition,
2011, J. Wiley & Sons, Inc.
3. Halman, J.P., Experimental Methods for Engineers, McGraw-Hill, Inc.
4. Doebelin, E.O., Measurement System: Application & Design, McGraw-Hill, Inc.
5. Beckwith, T.G., Marangoni, R.D. & Lienhard, J.H., Mechanical Measurements, Addison
Wesley, Inc.
6. Robert B. Northrop, Introduction to Instrumentation and Measurements, Second Edition,
Jun 28, 2005.
7. Alan S. Morris, Reza Langari, Measurement and Instrumentation Theory and Application
8. Alan S. Morris, Measurement and Instrumentation Principles, 3rd edition.

UNIT TASK
Weight Scale Calibration Procedure

1.0 Standards and Equipment The following equipment is required: Set of Known Weights NOTE:
Standards and equipment used must have a valid calibration certificate.
2.0 Calibration Procedure “Weight Scale Calibration Record Sheet” must be used. Clean the
Weight Scale’s measuring surface, the surface the scale is laid on, and wear gloves when
handling the weights to be used.

NOTE: Use a conversion factor of 0.453592 kg/lb to convert weights to Metric from Imperial

Step 1: Measure the ambient temperature and record it. If the temperature is 24o C, see the
Division Manager for further instructions.

Prepared by: Engr. Sandra E. Abancio, RMEE

 Step 2:
Test Characteristic: Leveling of scale surface
Test Method: Level the scale using its adjustable feet. There is a bubble-level just behind the
digital readout. If the scale cannot be leveled or one of the feet is broken, record it as
damaged/failed and notify the supervisor for further action. A granite surface is not entirely
necessary because the scale is self-leveling.
Acceptable Limit: Bubble is within the inner-marked circle.

Step 3:
Test Characteristic: Scale measurement
Test Method: Using a known weight, measure and record the scale’s calibration weight. Each
precision scale should have its own specified calibration weight that can be found in its manual
or in the manufacturer’s table of standard calibration weights. Use multiple smaller weights for
checking larger weight measurements if necessary. If it is required, remember to zero/tare the
scale after turning the scale on for the most accurate measurement. Do a final check by
measuring and recording 5 other weights over the range of the scale.
Acceptable Limit: +/- 2% of nominal weight value

3.0 Discuss the results of experiment.

Prepared by: Engr. Sandra E. Abancio, RMEE

Prepared by: Engr. Sandra E. Abancio, RMEE