Tuesday, February 8, 2011

Video: Experiment for Lux Meter


Video: Experiment for Stop Watch Time Study


Video: Experiment for Human Performance Rating


Video: Experiment for Sound Level Meter


Experiment Title: Stop Watch Time Study

Objective: To determine the standard time of an operation.

Equipment: Product to be assembled, tools for the operation, stopwatch, time
                    study form and table of allowance.

Procedure: 1. Divide the job into elements.
                    2. Conduct the stop watch time study and record the results in the
                        form provided. Record also the observed ratings.
                     3. If using continuous stop watch method, calculate the elemental
                    4. Calculate the number of observations required to achieve 95%
                        confidence level and ± 5% allowance error.
Where N = the number of readings to be determined
                                    n = the number of readings in taken in preliminary study
                                    x = the reading
                   5. Calculate the average rating.
                   6. Calculate the normal time.
                   7. Determine the allowance. (Table 1)
                   8. Calculate the standard time.

Table of Allowance

Allowance is the extra time added to the normal time to make the time standard practical and attainable.

There are 3 types of allowances:

1.    Allowance for personal time.
The time an employee is allowed for personal things such as going to the bathroom, getting a drink and other operator-controlled reason for not working.

2.    Fatigue allowance
The time an employee is allowed for recuperation from fatigue.

3.    Delay allowance
The time given for unavoidable delays that are beyond the operator’ s control such as waiting for instructions or material, machine breakdown and maintenance.

Table 1 shows the allowance for assembly operation suggested by ILO (International Labor Organisation)

Tuesday, January 25, 2011

Experiment for Rating of Human Performance

Introduction: Rating is the numerical value or symbol used to denote a rate of working (BS 3138). Standard rating is the rating corresponding to the average rate at which qualified workers will naturally work, provided that they adhere to the specified method and that they are motivated to apply themselves to their work. If the standard rating is consistently maintained and the appropriate relaxation is taken, a qualified worker will achieve standard performance over the working day or shift. The British Standard rating uses a scale of 0 to no activity and 100 to standard rating.

Objective:    To test ability to rate the performance of an operation.

Equipment: Jigs and pins, stopwatch, time study rater trainer form, table of ratings

                     1. Use the forms provided for this experiment.
2. Observe the task of assembling pins using two hands.
3. Measure using stopwatch the time taken to assemble all 30 pins for 10 cycles.
4. Fill up the forms and calculate the actual rating:

     Actual rating = Standard time / Actual time

5. Calculate the difference between the actual rating and your rating: 
     Difference = Actual rating – Your rating
     Difference = Your rating – Actual rating

6. Calculate the total rating score:

       Difference of 5% or less gets 10 points
       Difference of 6% to 10% gets 5 points
       Difference of more than 10% gets 0 point

7. Plot the ratings in the graph provided.

Work Study Equipment


A stopwatch is the equipment used to measure the amount of time elapsed from a particular time when activated to when it is deactivated. Digital electronics stopwatch is much more accurate than the mechanical stopwatch due to its crystal oscillator timing element.

This digital stopwatch has a jumbo display feature with digits 3/8" high, showing minutes, seconds, and 100ths of seconds. It times up to 30 minutes. It has time-out and accumulation features as well as a start/stop reset button. When it is not in stopwatch mode, it serves as a compact digital clock, showing hours, minutes, seconds, a.m. or p.m., day, and date. It continues to keep accurate time even when using the unit as a stopwatch. So, whenever you leave stopwatch mode, the unit will show the correct time of day. It runs on a single AA battery which will last more than a year. The unobtrusive black high-impact plastic housing is only 3.5" x 2.4" x .63" thick and the unit weighs only 2.5 ounces.


Stop Watch Mode

     1.     Press the mode button once, to reach stop watch mode from normal mode. The icons SU-
           FR-SA icons will flash when the stopwatch mode activates.
     2.    Activate the elapsed timer by pressing stop/start to start, making the SU-SA icons flash. Stop 
          the timer by pressing start/stop again, making the SU-FR-SA icons flash. Press start/stop to 
          restart, and stop again. Press mode to return to normal mode.
     3.    Activate split time by pressing stop/start to start, making the SU-SA icons flash. Press 
          split/reset to split, making the SU-TH-SA icons flash. Press split/reset to make the split 
          release, making the SU-SA icons flash, and press start/stop again to stop, making the SU-
          FR-SA icons flash. Press split/reset to reset the display. Press mode to return to normal 
     4.    Activate two-competitor timer by pressing the start/stop to start, making the SU-SA icons 
          flash. Press split/reset to split, making the SU-TH-SA icons flash, and press start/stop to stop, 
          making the SU-TH-FR-SA icons flash. Press split/release to make the split release, making 
          the SU-FR-SA icons flash, and press split/release to reset. Press mode to go back to normal 

How to Read??

·         Look at the first two digits on a digital stopwatch. Those numbers represent the minutes used. You can see a digital stopwatch in the picture to the left.
·         Look at the new two larger numbers after the ":" mark. Those numbers are the seconds used.
·         Look at the two smaller numbers after the second. Those numbers move much faster because they are the "hundredths of seconds" used.
·         Combine the number for your full time used. For instance 11:14:01 would be 11 minutes, 14 seconds and 01 hundredths of a second.
·         Some stopwatches also offer "lap" times in which a second button is pressed to measure each "lap" completed. The numbers are read in the exact same manner, however, you may have more than one time displayed. The picture to the left of this step shows a "lap-enabled digital stopwatch"; the bottom time is a combination of all the laps.

Time Study Rater Trainer Form

The time study rater trainer form is generally printed form of standard size which is used to record the data from the experiment so that the data can be filed neatly for reference as required by a well conducted time study.

The form comprises of 6 columns which are as below:

1.    Observation No.: the numbers of cycles to be conducted
2.    Your rating: the given rating according to our observation
3.    Observation time: the amount of actual observed time to be taken for the task
4.    Standard time: the amount of standard observed time for the task
5.    Actual rating: the actual rating according to the table of rating
6.    Difference: the differences between the actual rating and your rating

Table of Rating

Rating is one of the most controversial aspects of time study. It is largely matters of judgement and therefore is a subject of bargaining between management and labor. The work study specialist must have some means of assessing the rate of working of the operator he is observing and relating it to normal pace/performance. So, the table of rating is needed to compare the standard rate of operator with the actual rate of operator.

All these 3 equipments are used in one of the industrial experiments of the industrial engineering laboratory.

Experiment for Lux Meter

The sun has been our main source of illumination in many aspects of our daily life. However in certain circumstances artificial illumination is used. When an environment involved artificial illumination it is important to make sure that the illumination is designed to give satisfactory illumination level for the user.

Illumination is important because it deals with visibility level, colour and glare. In measuring illumination level, there are several types of quantities units involved. All the quantities are shown in table 1.

Experiment guide
Case A : with 100% light on in the Industrial Engineering lab

      a)      Measure the light intensity at locations A to F at table height.
      b)      Place the sensor facing the light source. Make sure that other group members are kept at a distance from the Lux Meter while measuring.
      c)      Select the suitable range, ( 300Lux, 1000Lux, or 3000Lux )

Case B : with 50% light on :
d)  Follow steps (a) to (c)

Case C :  Measure outdoors’ light intensity. 

Result Table

Lux Meter

Lux meter is a device that measuring luminous power per area. It will measured the intensity of the light that hit or came across human eyes. A light meter will  measures a subject's luminosity by gauging either reflective light or by incident light methods. Light meters measure either reflected light or incident light.

Experiment for Sound Level Meter

1.0          OBJECTIVE:                         DETERMINING THE NOISE LEVEL

2.0          EQUIPMENT:                   i)            Sound level meter
                                                               ii)            Controls

3.0          INTRODUCTION:             
A sound source radiates power and these results in a sound pressure. In this sense, the sound power is the cause and the sound pressure is the effect. The sound pressure is what we hear. Too high a pressure and prolong exposure will cause hearing damage and stress. Noise is any unwanted sound.

In ergonomics study – sound level is to be measured in dB(A). This is due to the fact that the A – filter is adapted to the physiology of the human ear. Table 1 shows the effect of noise on man.

Occupational Safety and Health Administration (OSHA) has established permissible noise exposure which depends on the duration of exposure shown in Table 2. The exposure to any sound level above 80dB causes the listener to incur a partial dose. If the total daily exposure consist of several partial exposures to different noise levels, then the several partial dose are added to obtain a combined exposure using the following formula:
D= 100(C1/T1 + C2/T2 +…………… + Cn/Tn) ≤ 100

Where:                   D = Noise dose
                                C = Time spent at specified noise level (hours)
                                T = Time permitted at specified noise level (hours) (refer Table 2)

The noise dose is then converted to an 8 hour weighted average (TWA) sound level using the formula:

TWA = 16.61 log (D/100) + 90

The TWA is the sound level that would produce a given noise dose if a person is exposure to that sound level continuously over an 8 hour workday. Thus a worker may be working in a safe environment based on the permissible noise exposure (Table 2) but the cumulative effect of this exposure based on TWA may proof otherwise.

A noise dose of 50% (TWA = 85 dBA) is the action level and 100% (90 dBA) is the permissible exposure level.

This experiment consists of the measurement of sound level in 3 different environments. In sound level measurement, as a precautionary step, windscreen should always be used when measurements are made outdoor or in very dusty environment, to ensure validity of measurement obtained, two aspects have to be considered;

i.              background noise must be low enough
ii.             Sound level meter should be held at arm length or mounted on a tripod (to minimize 
               disturbances of the sound field due to the operator’s body)

                   a)      Set the Range Selector switch to the appropriate measuring range for the 
                           proposed measurement.
                   b)      Set the Detector Response switch as follows;
“Fast”    :               For relatively steady sound levels
“Slow”  :               For relatively fluctuating sound levels
c)    Select “Man” mode
d)    Switch the Power switch to “ON”
e)    Note the displayed value
f)     Press the Reset button
g)    Measure the same sound source for the second time
h)    Turn the Power switch “OFF”
i)     Go through step (a) to (e) again for 2 other sound sources.

5.0          RESULTS:

Sound Level Meter

A sound level meter is an instrument planned in response to sound around in the same manner like the human ears and provide objective, reproduced to measurements sound pressure level. There much different sound measuring system available. Even though different in detail, each consisting of a microphone system, the processing and read-out unit.

  In experiment that we will do later, the type of sound level meter who we use is the model CENTER 320 series.
 The model specifications are….
·         Mini Size
·         Newly Design Shape
·         Low Cost High Performance
·         MAX/MIN Function
·         Level Range Display  
·         AC  Signal Output
·         Resolution 0.1 dB 
·         IEC 651 Type II
·         Microphone:
   Electric condenser microphone
·         Accuracy:
    ±1.5 dB ( ref 94dB @1KHz )
·         Level Range:
    Low = 35 ~ 80 dB
    Medium = 50 ~ 100 dB
    High = 80 ~ 130 dB
·         Frequency Weighting:
    A , C
·         Time Weighting:
    Fast , Slow
·         Auxiliary Outputs:  
    AC Signal Output
·         Dynamic Range:
    50 dB
·         Frequency Range:
    31.5Hz to 8KHz
·         Battery Type:
   9V Battery NEDA 1604, IEC 6F22, JIS 006P
·         Battery Life: 
    50 hours ( with alkaline battery )
·         Operation Temp.: 
    0ºC~ 40ºC (<80% R.H.)
·         Storage Temp.:
    -10ºC~ 60ºC (<70% R.H.)
·         Dimension: 
    232mm x 54mm x 34mm ( 9.1" x 2.1" x 1.3" )
·         Weight:
    Approx. 200g
·         Accessories:
    Manual, 9V Battery, Calibration Screwdriver, Windscreen

    Methods for using that the instrument we will be explain in procedures experiment later.

    From the instrument, the data that we can obtain is Noise level in a unit dBA and from it, we can get
  permissible time of expose (hour) from OSHA table and effect of noise pressure to human.

Introduction of Work Study

What is ‘Work Study’?
According to the British Standard Institution, work study is a systematic examination of activities in order to improve the effective use of human and other material resource. In work study there is three assumptions in work study which are :
      a)      There is always more than one method to do a task or a job.
      b)      Solving problem through scientific methods is better than other method and the
      c)      Work can be measured in time unit.

Work study can be derived into two components :

The objective of work study is to find the best and most efficient way of using the available resources such as men, material and machinery. In other words, to produce the high quality production in the best minimum possible time. The time required to produce a product is depends on the manufacturing procedure and method study aims at finding the best possible manufacturing procedure which involves least time and does not cause fatigue to the workers.
Method study is one of principal techniques by which work content in the product manufacture or process could be decreased and according to the British Standard Institution method study is a systematic recording and critical examination of ways of doing a job in order to make improvement. This can be achieved by eliminating or reduce the unnecessary movement of the workers. It can be done by combining the operations, or by changing the sequence of the operations to simplify the whole operation system in order to save men energy, sources and material involved.

By applying method study, the work measurement is the next important steps to find out the time required to complete the operations. Work measurement is useful to find out the time allowed to complete the job using the selected method. Work measurement is defined by British Standard Institution as the application techniques designed to find out the time for the qualified worker to carry out a task at the defined rate of working. The time resulted from the measurement is normalized and converted into standard time and work method is called standard method.

What are the advantages of  ‘Work Study’ ?
There is four major advantages of work study which are :
      a)      Higher productive efficiency.
      b)      Create better employee-employer relations.
      c)      Provide better service to customers.
      d)     Provide better working conditions to the employee and employer.

What are the advantages that can be obtain from ‘Method Study’ ?
Method study are useful to :
      a)      Improved working processes and standardized procedures.
      b)      Create better work place layout which is more neat and clean environments and working conditions.
      c)      Reduce fatigue to the operators.
      d)     Produce better product quality.
      e)      Bring out the effective used of men, materials and machinery.

What are the advantages that can be obtain from ‘Work Measurement’ ?
Work measurement are important to :
      a)      Determine the time required to do a job which the time obtain will be compared to alternative method and     define the fastest method.
      b)      Determine the resources required, budgeting and costing for a job.
      c)      Provides information for effective production planning and maintenance procedures.
      d)     Aids in calculating exact delivery dates.
      e)      Provides a basis for fair and sound incentive schemes.