Development of special measuring tool for trace of micro force value


ACTA IMEKO | www.imeko.org December 2020 | Volume 9 | Number 5 | 270 

ACTA IMEKO 
ISSN: 2221-870X 
December 2020, Volume 9, Number 5, 270 - 273 

 
 

DEVELOPMENT OF SPECIAL MEASURING TOOL FOR TRACE OF 

MICRO FORCE VALUE 
 

Li Yang1, Shi Wei2, Tao Jizeng3 

 
1 Changcheng Insitiute of Metrology & Measurement, Beijing, China, ly304cimm@126.com  

2 Changcheng Insitiute of Metrology & Measurement, Beijing, China, swlltm@126.com  
3 Changcheng Insitiute of Metrology & Measurement, Beijing, China, tjz＿75@163.com 

 

Abstract: 

This paper introduces the development of the 

special traceability measuring tool for micro force 

value with the test force range of 0.009807 N ~ 

9.807 N(1 gf~1 kgf) and the accuracy of better than 

± 0.1%, including the selection of the 

electromagnetic balance module, the design of the 

hardware structure, and the compilation of the 

software program. Finally, the special traceability 

measuring tool integrating the test measurement, 

automatic data collection and automatic data 

processing is realized, and the test verification result 

is given 。  It provides a method to solve the 
problem of trace the small force value of existing 

micro Vickers hardness tester and Knoop hardness 

tester. 

Keywords: micro force, measuring tool, 
traceability, micro Vickers hardness, Knoop hardness 

1. INTRODUCTION 

With the development of modern material 

surface engineering, such as Physical vapor 

deposition, magnetron sputtering, ion implantation, 

surface modification, thermal spraying, nitriding 

and carburizing, etc., the thickness of micro Vickers 

hardness and Knoop hardness test samples or the 

surface modified layer on the sample surface is 

getting thinner and thinner, and the hardness test 

force value is getting lower and lower, reaching 

0.009807 N. However, the minimum measuring 

range of the existing force measuring instrument is 

1 N. According to the principle of one tenth use, the 

minimum measurement can be 0.1 N, which can not 

meet the existing requirements.  Therefore, it is very 

necessary and urgent to develop the special 

traceability measuring tool with the lower limit of 

0.009807 N. 

2. PROJECT DESIGN 

In this paper, the special traceability measuring 

tool for micro force value is developed, which has 

the force value range of 0.009807 N ~ 9.807 N(1 

gf~1 kgf) and the accuracy of better than ± 0.1%. It 

selects the electromagnetic balance module as the 

core, and carries on the package design to it, has 

realized the test measurement, the data automatic 

collection, the data automatic processing as a whole 

special traceability measurement tool, specifically 

includes, the electromagnetic balance module 

selection design, the hardware structure design, and 

the software programming three parts. 

The output value of the balance is the mass. The 

relationship between the force value and the mass is 

shown in formula (1). 

𝐹 = 𝑚𝑔 (1 −
𝜌1

𝜌2
) (1) 

In the formula: 

F - force value , N; 

m - mass , kg; 

g - the local acceleration of gravity in the 

laboratory , m/s2; 

𝜌1 -air density , kg/m
3; 

𝜌2 -weight density , kg/m
3. 

Since the density of the weight is far greater than 

that of the air, 
𝜌1

𝜌2
 is negligible. 

2.1 Selection and design of electromagnetic 

balance module 

According to the research, referring to the test 

requirements, working space of most hardness tester 

and other factors, by selecting the range, accuracy, 

geometric dimension and other indicators of 

electromagnetic balance module, the two 

electromagnetic balance modules of sartorius are 

finally selected, their models are WZA224-N and 

WZA1203-N, as shown in Figure 1, and their 

technical indicators are shown in Table 1. 

     
a) WZA224-N                     b) WZA1203-N 

Figure 1 electromagnetic balance modules 

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ACTA IMEKO | www.imeko.org December 2020 | Volume 9 | Number 5 | 271 

Table 1 Technical indicators of lectromagnetic balance 

modules 

Model WZA224-N WZA1203-N 

Weighing 

Capacity(g) 
220 1200 

Readability(mg) 0.1 1 

Maximum 

deviation(mg) 
±1 ±5 

Standard deviation 

determined(mg) 
0.1 1 

Maximum 

Linearity(mg) 
±0.2 ±2 

Physical 

dimension(mm) 
181ⅹ67ⅹ73 200ⅹ67ⅹ78 

 

Although the electromagnetic balance module 

with the smallest geometric size is selected on the 

premise of meeting the requirements of technical 

specifications, its length and width meet the 

requirements of micro Vickers hardness tester in our 

laboratory. Because the size of the micro Vickers 

hardness tester in our laboratory is 200 mm ⅹ 280 
mm. But its height is still higher than the working 

space height of most hardness machines, including 

those in our laboratory. Therefore, it is necessary to 

reform the selected electromagnetic balance module, 

remove its own measuring head and replace it with 

a thinner force measuring base. Because the selected 

balance module is a mature commodity, it has a 

certain stiffness, and because the indenters used in 

micro Vickers hardness test and Knoop hardness 

test are diamond indenters, it is necessary to set a 

ceramic force measuring unit in the center of the 

force measuring seat to ensure its stiffness in use 

and reduce the impact on the test results. The 

designed balance module has good stiffness, which 

can reduce the influence of the deformation of the 

worktable on it in the use process. The accuracy of 

the design and operation is ± 0.01%, and the 

influence of the table deformation can be 

ignoredThe design drawing of electromagnetic 

balance module transformation is shown in Figure 

2. 

 

Figure 2 Design drawing of electromagnetic balance 

module transformation 

 

2.2 Hardware structure design 

The special measuring tool for trace of micro 

force value is often carried out, so it needs to be easy 

to carry, simple to make mistakes, and anti-collision 

and other functions. Therefore, hardware structure 

design should be carried out on the basis of 

electromagnetic force balance module. The 

hardware structure design diagram is shown in 

Figure 3. 

 

Figure 3 Hardware structure design drawing 

After completion, the special measuring tools for 

trace the micro force value include the box with pull 

rod, industrial computer, mouse, power supply, two 

modified electromagnetic balance modules and 

their corresponding control board, level meter, 

leveling nut, etc. 

The box with pull rod is made of aluminum alloy 

with light weight, high strength and easy to carry 

and move. The box is filled with thick sponge to 

protect internal parts. The industrial computer is 

used for operation test, collection and processing of 

test data. The level meter and leveling nut are used 

to ensure the level of the device during the test. The 

WZA224-N module and WZA1203-N module are 

used for test force The control module is used to 

control the electromagnetic balance module, and the 

trunking and mouse are used to link and operate. 

2.3 Programming and design of software 

In order to reduce the error of manual calculation, 

the special traceability measurement tool for micro 

force value is designed and compiled with 

supporting automatic processing software, which 

adopts automatic reading, automatic calculation and 

other functions. 

 

Figure 4 Automatic processing software interface 

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ACTA IMEKO | www.imeko.org December 2020 | Volume 9 | Number 5 | 272 

As shown in Figure 4, the automatic processing 

software is divided into four areas, namely: 

a）Serial port setting area 
The serial port can be set in this area for 

communication with the electromagnetic balance 

module. 

It is written in C# language, using standard serial 

port communication protocol and SBI 

communication protocol based on te series 

electronic balance module. The communication 

steps are as follows: 

Create serial port: serialport SP1 = new 

serialport(); 

Open the serial port: Sp1. Open(); 

Read serial data: Sp1. Readline(); 

Close the serial port: Sp1. Close(); 

As shown in Figure 5, analyze the data according 

to the SBI protocol of the electromagnetic balance 

module, take the first to the 14th bit of data, remove 

the useless space, and display the data on the 

interface. 

 

 

Figure 5 SBI communication protocol of 

electromagnetic balance module 

b）Data configuration area 
In this area, we can select the reference standards, 

model and measurement standard value, and have 

the function of clearing before the test. 

Reference standards include ISO 6507 Metallic 

materials – Vickers hardness test, ASTM E 92 

Standard test methods for Vickers hardness and 

Knoop hardness of metallic materials, ASTM E 384 

Standard test method for microindentation hardness 

of materials, and JJG 148 Verification regulation of 

Vickers hardness reference blocks, and JJG 151 

Verification regulation of metallic Vickers hardness 

testers. 

Refer to the protocol of electromagnetic balance 

module, as shown in Figure 6, set the equipment 

reset function, and the command format is as 

follows: 

sp1.WriteLine("ESC\rV\r\n"); 

 

 

Figure 6 protocol of electromagnetic balance module 

c) Data collection area 

This area is used to display the collected and 

processed data. 

d) Operation button area 

Buttons in this area are used for software 

operation, including value taking, backward, clear, 

save and exit. 

After data acquisition, when the "value taking" 

button is pressed, the software will intercept the 

current test value and save it to the data acquisition 

area. The backward button deletes the last data in 

the acquisition area. The clear button clears all data 

in the data collection area. The save button saves the 

data in the data collection area to the record report. 

The exit button will push out of the system 

Physical drawing of development of the special 

traceability measuring tool for micro force value, as 

shown in Figure 7. 

 
Figure 7 Physical drawing of development of the special 

traceability measuring tool for micro force value 

 

2.4 Test verification 

In order to verify whether the special measuring 

tool for tracing of micro force value meets the 

required technical indicators, the test is carried out. 

See Table 2 for the standard measuring instruments, 

and see Table 3 for test results. 

Table 2 Standard measuring instruments 

Name Model Accuracy level Number 

Standard 

weights 
1mg～1g E2 1 sets 

Standard 

weights 
1g～6kg E2 1 sets 

 

It can be seen from table 3 that the accuracy and 

repeatability of the development of the special 

traceability measuring tool for micro force value are 

0.005% and 0.003%, meeting the design and use 

requirements. 

 

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ACTA IMEKO | www.imeko.org December 2020 | Volume 9 | Number 5 | 273 

Table 3 Test Results 

Standard 

value 

(g) 

Test 

value 

(g) 

Error 

(%) 

Repeatability 

(%) 

1.0000 1.0000 0.000% 0.001% 

2.0000 2.0001 0.005% 0.000% 

5.0000 5.0002 0.004% 0.001% 

10.0000 10.0000 0.000% 0.001% 

20.0000 20.0002 0.001% 0.002% 

50.0000 50.0000 0.000% 0.000% 

100.0000 100.0009 0.001% 0.001% 

200.0000 200.0012 0.001% 0.000% 

300.000 300.001 0.000% 0.002% 

500.000 500.000 0.000% 0.000% 

1000.000 1000.001 0.000% 0.003% 

3. SUMMARY 

This paper introduces the development of a 

special measuring tool for micro force traceability, 

which has a measuring force range of 0.009807 N ~ 

9.807 N (1 gf ~ 1 kgf), and the accuracy is better 

than ± 0.1%. It includes the selection of 

electromagnetic balance module, the design of 

hardware structure, the determination of 

measurement accuracy, and the compilation of 

software program. Finally, a special traceability 

measuring tool which integrates measurement, 

automatic data acquisition and data processing is 

realized, and the experimental verification results 

are given. At the same time, it has been well applied 

in our laboratory. The special inspection tool for 

trace of micro force provides a new method to solve 

the problem of micro force traceability of micro 

Vickers hardness tester and Knoop hardness tester. 

The next step is to develop a small force traceability 

tool with smaller geometry for most micro Vickers 

and Knoop hardness machines. 

4. REFERENCES 

[1] ISO/TC 164, ISO 6507: Metallic materials-Vickers 
hardness test, 2018. 

[2] ASTM E92 Standard test methods for Vickers 
hardness and Knoop hardness of metallic materials, 

2017. 

[3] ASTM E384 Standard test method for 
microindentation hardness of materials, 2017 

[4] JJG 148 Verification regulation of Vickers 
hardness reference blocks, 2006. 

[5] JJG 151 Verification regulation of metallic Vickers 
hardness testers, 2006. 

[6] Liu Maochun. Li Qi, C # program development 
case class. New: tsinghua university press, Ch14, 

pp. 299-362, 2018.  

 

 
 

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