Triple Beam Balance – Parts, Procedure, Uses

Triple beam balance is a mechanical instrument used for measuring the mass of an object. It does not need electricity. So it can be used in ordinary laboratory and classroom.

It measures mass, not weight. So the reading is not changed by local gravity like weight. The mass is measured by balancing the object with known sliding weights.

The balance works on lever principle. It has one weighing pan and three beams. These beams are called front beam, middle beam and back beam.

Each beam has a sliding weight. These weights are called riders or poises. The riders are moved along the graduated scale until the pointer comes to zero mark.

When the pointer becomes balanced at zero, the readings of three beams are added together. This gives the total mass of the object. A common triple beam balance can measure up to about 610 g with 0.1 g accuracy.

The idea of balance is very old and was used in ancient time. The three beam balance was first developed by Joseph Louis Gay-Lussac in 1830. The practical laboratory triple beam balance was later made by Frank Aronson in 1906.

Later Paul Klopsteg improved the design. The OHAUS Corporation also added better bearings and magnetic damping. These changes made the balance more stable and easy to use in laboratory.

Principle of Triple Beam Balance

Principle of Triple Beam Balance is based on the principle of moment equilibrium or law of lever. It works like a simple lever system.

In this balance the fulcrum is present between the load and the balancing weights. So it acts as a first class lever. The object is placed on the weighing pan on one side.

The object produces downward force on the pan. This produces turning effect or torque on one side of the balance. To balance this force, riders are moved on the three beams.

The riders are known masses. They are shifted along the graduated beams until the pointer comes at zero mark. At this point both sides of the balance become equal.

When the torque produced by object is equal to the torque produced by riders, the beam becomes balanced. This condition is called equilibrium.

The readings of all three riders are then added together. This gives the mass of the object. Since gravity acts equally on object and riders, the balance measures mass and not weight.

Parts of Triple Beam Balance With Diagram

The following are the main parts of Triple Beam Balance–

1. Base
   It is the lower supporting part of the balance. It holds all parts in proper position and keeps the balance stable on the table.
2. Weighing pan
   It is the flat plate where the object is placed for weighing. It is usually made up of stainless steel.
3. Beams
   These are the three parallel metal bars of the balance. They are marked with graduated scales for measuring mass.
4. Front beam
   It is the front scale of the balance. It gives smaller reading and is used for fine adjustment of mass.
5. Middle beam
   It is one of the main beams. It usually gives larger mass reading and has notches for placing the rider.
6. Rear beam
   It is the back beam of the balance. It also has graduated marks and notches for the rider.
7. Notches
   These are grooves present on the beams. They hold the riders at fixed measurement points.
8. Riders
   These are sliding weights present on the beams. They are also called poises or counter masses.
9. Pointer
   It is present at the right side of the balance. It moves up and down when riders are adjusted.
10. Zero mark
    It is the fixed line present near the pointer. The balance is correct when pointer aligns with this mark.
11. Zero adjustment knob
    It is used to bring the pointer at zero before weighing. It helps in setting the balance properly.
12. Magnetic damper
    It is used to reduce swinging of the beam. It helps the pointer to become stable quickly for taking reading.

Operating Procedure of Triple beam balance

The following are the operating procedure of Triple Beam Balance–

1. At first the balance is kept on a plain stable table. The pan is checked and cleaned.
2. All the three riders are brought to zero position. They are kept at the left side of the beams.
3. The pointer is observed. It should remain at the zero mark before weighing.
4. If the pointer is not at zero, the zero adjustment knob is turned slowly. The pointer is set with the zero line.
5. The object is kept at the centre of the weighing pan. The pan should not be touched or pressed by hand.
6. The largest rider is moved first. It is moved notch by notch towards right side.
7. When the pointer goes below zero, the rider is brought back one notch. The rider should sit properly in the notch.
8. The middle rider is then moved. It is also moved towards right side until the pointer goes below zero.
9. The middle rider is then returned one notch back. This gives the nearest lower mass reading.
10. The smallest rider is moved at last. It is moved slowly on the front beam.
11. The smallest rider is adjusted until the pointer comes exactly on zero mark. At this point the balance becomes balanced.
12. The readings of three beams are taken. All the readings are added together.
13. The sum of the three readings gives the mass of the object. The mass is written in gram (g).

Advantages of Triple Beam Balance

The following are the advantages of Triple Beam Balance–

• It works by mechanical principle. So it does not need electricity or battery and can be used during power failure or field work.
• It is made up of strong metal parts. It is less affected by moisture, small impact and temperature change than electronic balance.
• It is cheaper than digital balance and analytical balance. It also needs less maintenance because no electronic circuit is present.
• It does not produce electric spark because no electricity is used. So it is safer in place where flammable vapour or combustible dust may be present.
• It measures mass by comparing unknown object with known sliding weights. So local gravity effect is cancelled and true mass is obtained.
• It gives consistent reading when the balance is zeroed and riders are adjusted properly. Same object gives same mass reading.
• It is useful for teaching students. The visible beam and riders help to understand lever, torque and equilibrium.
• It gives hands-on practice of weighing. Students can directly see how the object mass is balanced by the riders.

Limitations of Triple Beam Balance

The following are the limitations of Triple Beam Balance–

• It has lower precision than digital balance. Usually it measures up to 0.1 g only, so very small mass change cannot be measured properly.
• It takes more time for weighing. The riders must be moved by hand until the pointer comes to zero mark.
• It depends on the user’s skill. Wrong rider position, wrong reading and wrong estimation may give error in mass.
• It may show parallax error. If the pointer is not observed at eye level, the reading may be taken wrongly.
• It needs practice for correct use. A new user may take time to understand the rider movement and reading of three beams.
• It can be damaged by sudden shock. Dropping heavy object on the pan may damage the knife edges and reduce sensitivity.
• Its moving parts need proper care. Dust or metal particles near damping magnet may make the beam movement slow or sticky.
• It must be kept on level and stable surface. Vibration, air draft and temperature change may disturb the pointer and affect the reading.

Uses of Triple beam balance

The following are the uses of Triple Beam Balance–

• It is used in science classroom for teaching mass measurement, comparing masses and explaining basic physics principle like lever, torque and equilibrium.
• It is used in chemistry laboratory for weighing solids, liquids and powders, which are needed for preparation of chemical solution, percent composition and molar quantity calculation.
• It is used in physics experiments for measuring mass of object, which is then used for calculation of density, force, momentum and energy.
• It is used in biology and environmental field research for weighing soil sample, plant biomass and biological specimens, and it is useful in remote place because it does not need electricity.
• It is used in pharmaceutical formulation work for rough weighing and compounding of drug ingredients before more sensitive analytical weighing.
• It is used in food and beverage production for weighing bulk ingredients, spices and liquids, so the recipe and product quality remain uniform.
• It is used by jewellers for weighing gemstones and precious metals like gold and silver, because it is mechanical and not affected much by electromagnetic disturbance.
• It is used in industrial quality control for weighing raw materials and small manufactured parts, so the products can be checked according to required specification.

Precautions of Triple Beam Balance

The following are the precautions of Triple Beam Balance–

• Chemicals and corrosive substances should not be placed directly on the weighing pan. Weighing paper, weighing boat or glass container should be used and the object should be clean and dry.
• The balance and surrounding area should be kept clean. Any spill should be cleaned immediately and lubricants should not be applied on knives or bearings.
• Heavy objects should not be dropped on the pan. Sudden shock may damage the agate or steel knife edges and the sensitivity of the balance becomes less.
• The balance should be carried carefully during shifting. One hand should be kept under the base and the pan support should be held to prevent jerking of knife blades.
• The balance should be placed on smooth, level and stable surface. Vibration, air draft and contact with other objects should be avoided.
• Movement around the balance should be less during weighing. The balance is sensitive to motion and the pointer may not become stable.
• The balance should be zeroed before weighing. The pan must be empty and the pointer should remain at zero mark.
• The object should be placed at the centre of the pan. If the object is placed at one side, unequal load may give wrong reading.
• The riders should be seated properly in their notches. If the rider is not placed exactly in notch, the mass reading becomes incorrect.
• Reading should be taken at eye level. If the pointer is seen from above or below, parallax error may occur.
• After use, all riders should be returned to zero position. The pan should be kept empty and clean.
• The balance should be stored in dry and stable place. Extreme humidity and temperature should be avoided.

References

1. UCSB Physics. (n.d.). 40.39 — Damping of eddy current pendulum.
2. BCIT Commons. (n.d.). DEM44 eddy current induced in flat aluminum ring.
3. Accurate Meezan Oman. (2026, May 8). Digital scales vs triple beam balances: What is the difference?
4. Physics 12 Portfolio Project. (n.d.). Driving question.
5. Harvard Natural Sciences Lecture Demonstrations. (n.d.). Eddy current damping.
6. Lumen Learning. (n.d.). Eddy currents and magnetic damping | Physics.
7. OpenStax College. (2012). Eddy currents and magnetic damping – College physics.
8. Scales Plus. (2025, June 20). Fun facts about the weighing industry.
9. Adam Equipment. (2019, February 1). How to calibrate a triple beam balance.
10. WANT Balance Instrument Co., Ltd. (2026, March 10). How to choose the right electronic scale balance for your laboratory.
11. Home Science Tools. (n.d.). How to use & calibrate a triple beam balance.
12. The Physics Universe. (n.d.). How to use a triple beam balance (Step-by-step) [Video]. YouTube.
13. Scale Man. (2023, January 4). How to use a triple beam balance. Central Carolina Scale Learning Center.
14. Certified MTP. (2023, May 30). How to use a triple beam balance.
15. Introducing measurements in the laboratory. (n.d.).
16. Welso. (2026, March 17). Laboratory electronic balance classification and selection guide. Shanghai Welso Technology Co., Ltd.
17. Mass determination with laboratory balances. (n.d.). Chymist.com.
18. DSCBalances. (2025, May 12). Mastering precision: How to read triple beam balance accurately.
19. Advanced Instructional Systems, Inc., & University of North Carolina. (2011). Measurements and error analysis. WebAssign.
20. Alloprof. (n.d.). Measuring mass | Secondaire.
21. W&J Instrument Co., Ltd. (2025, September 13). Mechanical analytical balances vs. digital: Which is better for your lab?
22. OHAUS Corporation. (n.d.). OHAUS© triple beam balance trouble-shooting guide.
23. Qualitest Team. (2026, February 20). Precision balance vs analytical balance: Which to buy? Worldoftest.
24. Adam Equipment. (n.d.). TBB triple beam balances.
25. ExploreLearning. (n.d.). Teaching students how to use a triple beam balance – Gizmos.
26. Technical analysis of the triple beam balance: Evolution, mechanical engineering, and metrological application in laboratory environments. (n.d.).
27. Techniques and measurements. (n.d.).
28. Precisa. (n.d.). The history of the weighing scales | Weighing balances through the ages.
29. OHAUS. (n.d.). Timeline.
30. Triple beam balance. (n.d.).
31. OHAUS. (n.d.). Triple beam balance.
32. SMU Physics. (n.d.). Triple beam balance.
33. San Diego Scale. (2025, September 17). Triple beam balance essential tips for accurate measurements.
34. Gossett-Webb, S., & Chesnutt, B. (n.d.). Triple beam balance | Definition, parts & use. Study.com.
35. Scales Plus. (n.d.). Triple beam balances.
36. Wikipedia contributors. (2025, August 13). Triple beam balance. Wikipedia, The Free Encyclopedia.
37. jbru15. (n.d.). Using a triple-beam balance with uncertainty analysis : 15 steps. Instructables.
38. Chesnutt, B. (n.d.). Video: Triple beam balance | Definition, parts & use. Study.com.
39. W&J Instrument Co., Ltd. (2024, April 21). What is triple beam balance in laboratory apparatus.
40. DSCBalances. (2025, December 13). What is the instrument used to measure mass?
41. W&J Instrument Co., Ltd. (2024, April 19). What is the use of triple beam balance in laboratory.
42. Mona. (2025, December 5). Which type of balance is more accurate? Weigherps.
43. Common apparatus and basic techniques. (n.d.).
44. Brooklyn College. (n.d.). Static equilibrium.