Automatic Bulk Weighing Systems

EPO ABWS (Rev. 08/14) DRAFT Page 1

EPO No. 16

Appendix B

High-Level Steps to Performing the Increasing-Load Test Using the 

Substitution or Alternative Substitution Test Method

Listed below are the high-level steps necessary to properly perform an increasing-load 

test on a scale with digital indication using the substitution or alternative substitution test 

method. For detailed instructions on how to perform each of these steps refer to 

Appendix B (Supplement 1) titled “Applying the High-Level Steps of the Substitution 

and Alternative Substitution Test Method.” For additional clarification on determining 

the amount of scale error and evaluating the results of tests when using the substitution 

test method, refer to Appendix B (Supplement 2) titled “Determining Scale Error When 

Applying the Substitution Test Method.” For additional clarification on determining the 

amount of scale error and evaluating the results of tests when using the alternative 

substitution test method, refer to Appendix B (Supplement 3) titled “Determining Scale 

Error When Applying the Alternative Substitution Test Method.”

Step 1) Establish a proper reference at no load: With no load on the load-receiving 

element of the scale, add error weights equal to the value of 0.1 d to establish a

proper reference at no load. Make note of the total value of the error weights on 

the scale; then remove the error weights.

Step 2) Apply the test weight and then use error weights to establish a proper 

reference: Apply the first test load consisting entirely of test weight. Then add 

error weights equal to the value of 0.1 d to adjust the weight of the load so that a

proper reference is established between two adjacent increments. Make note of 

the total value of the error weights on the scale; then remove the error weights.

Step 3) Determine the amount of scale error: 

(a) Determine the amount of error in the scale for each test load applied using 

the error formula:

En = Ie – Is – L + Rs – Re

Where:

“En” (Error) represents the amount of error in the scale relative to the applied 

test weight portion of the total applied load;

“Ie” (Indication ending) represents the scale indication after the test weight has 

been applied and proper reference established;
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“Is” (Indication start) represents the scale indication before the test weight was 

applied;

“L” (Load) represents the value of the applied test weight excluding any 

substituted load;

“Rs” (Reference start) represents the value of the error weights on the 

load-receiving element that established proper reference prior to the test weight 

being applied; and

“Re” (Reference ending) represents the value of the error weights on the 

load-receiving element that established proper reference after the test weight 

had been applied. 

(b) Sum the cumulative errors (ΣEn) for all steps of the substitutions.

Step 4) Remove the test weight and determine the amount of any no-load balance 

change: Remove the first test load and add error weights to return to the proper 

reference at no load. Any difference in error weights from Step 1 represents a 

change in the no-load balance reference. Discontinue testing if no-load balance 

is unstable or does not repeat to within the value of minimum tolerance each

time a test load is applied and then removed. 

If no change has occurred or the amount of change does not exceed minimum 

tolerance, testing may continue. However, in the latter case it will be necessary 

to make note of the value of the error weights needed to re-establish proper 

no-load reference. Once you’ve made note of the value of the error weights that 

establishes the no-load reference, remove the error weights from the scale.

Step 5) Create the first substitution test load: Create the first substitution test load by 

loading bulk material onto the load-receiving element of the scale. 

Substitution Test

Apply trim weights, as necessary, to increase the weight of the first substitution 

test load to that which was first indicated when the test weight was first applied 

in Step 2.

Alternative Substitution Test

Apply trim weights, as necessary, to increase the weight of the first substitution 

test load so that it’s indicated weight is slightly less than (i.e., no more than 5 

divisions) the value indicated when the test weight was first applied in Step 2.
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Then add error weights equal to the value of 0.1 d to establish a proper 

reference for the first substitution load. Make note of the total value of the 

error weights on the scale; then remove the error weights.

Step 6) Apply test weight to the first substitution test load and use error weights to 

establish a proper reference: Apply the test weight to the first substitution test 

load. Then add error weights equal to the value of 0.1 d to adjust the weight of 

the load so that a proper reference is established between two adjacent 

increments. 

Step 7) Determine the amount of scale error: Determine the amount of error in the 

scale using the error formula provided in Step 3. Then remove the test weight, 

all error weights, and any trim weights that were added in Step 5 from the 

load-receiving element. 

Step 8) Create the second substitution test load: Create the second substitution test 

load by loading bulk material onto the load-receiving element of the scale. 

Substitution Test

Apply trim weights, as necessary; to increase the weight of the second 

substitution test load to that which was first indicated when the test weight was 

applied in step 6.

Alternative Substitution Test

Apply trim weights, as necessary, to increase the weight of the second 

substitution test load so that it’s indicated weight is slightly less than (i.e., no 

more than 5 divisions) the value indicated when the test weight was first applied 

in Step 6. 

Then add error weights equal to the value of 0.1 d to establish a proper 

reference for the second substituted load. Make note of the total value of the 

error weights on the scale; then remove the error weights.

Step 9) Apply test weight to the second substitution test load and use error weights to 

establish a proper reference: Apply the test weight to the second substitution 

test load. Then add error weights equal to the value of 0.1 d to adjust the weight 

of the load so that a proper reference is established between two adjacent 

increments. 

Step 10) Determine the amount of scale error: Determine the amount of error in the 

scale with the test load applied using the error formula indicated in Step 3.

Then remove the test weight, all error weights, and any trim weights that were 

added in Step 8 from the load-receiving element. 
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Step 11) Create the third substitution test load: Create the third substitution test load by 

loading bulk material onto the load-receiving element of the scale. 

Substitution Test

Apply trim weights, as necessary; to increase the weight of the third substitution 

test load to that which was first indicated when the test weight was applied in 

step 9.

Alternative Substitution Test

Apply trim weights, as necessary, to increase the weight of the third substitution 

test load so that it’s indicated weight is slightly less than (i.e., no more than 5 

divisions) the value indicated when the test weight was first applied in Step 9. 

Then add error weights equal to the value of 0.1 d to establish a proper reference 

for the third substituted load. Make note of the total value of the error weights 

on the scale; then remove the error weights.

Step 12) Apply test weight to the third substitution test load and use error weights to 

establish a proper reference: Apply the test weight to the third substitution test 

load. Then add error weights equal to the value of 0.1 d to adjust the weight of 

the load so that a proper reference is established between two adjacent 

increments. 

Step 13)Determine the amount of scale error: Determine the amount of error in the 

scale using the error formula indicated in Step 3.

Substitution Test

Note: If after completion of three substitutions from the no-load reference, 

additional test loads are still needed to make possible a test to at least used 

capacity, it will be necessary to use a strain load to increase the loading of the 

scale to the appropriate area where additional testing is needed. Once the strain 

load has been created and proper reference established for the load, up to three 

substitution test loads can be created from that strain load using the same 

procedures outlined in this appendix. 

Alternative Substitution Test

Note: If after completion of three substitutions from the no-load reference, 

additional test loads are still needed to make possible a test to at least used 

capacity, continue applying these same procedures, using as many additional 

substitution test loads as are needed, to complete the test.