Czech Metrology Institute  
Okružní 31, 638 00 Brno  
 
1. ------IND- 2018 0331 CZ - EN- ------ 20180803 --- --- PROJET 
Executive summary for the EC (not part of this legislation)  
Tendon assemblies for prestressed concrete and rock anchors are subject to national metrological 
regulation – initial verification and follow -up verification at the specified intervals when they are put 
into use and during subsequent use. The subject of this regulation is to lay down metrological and 
technical requ irements for these measuring instruments, including the testing methods for the initial 
verification and follow -up verification of these measuring instruments already put into use.  
The requirements imposed on these measuring instruments when in use are bas ed on the document 
ETAG 013 from June  2002.  
 
 
Contact person: Hendrych Tomáš, 
Mgr.  
Telephone: 545  555 414 
 
PUBLIC DECREE  
 
As the authority with substantive and territorial jurisdiction in the matter of laying down metrological 
and technical requirements fo r specified measuring instruments and stipulating test methods for type 
approval and verification of specified measuring instruments pursuant to §  14(1) of Act No  505/1990, 
on metrology, as amended, and in accordance with the provisions of §  172 et seq. of  Act No  500/2004, 
the Code of Administrative Procedure (hereinafter the AC), the Czech Metrology Institute (CMI) 
commenced ex officio proceedings on 26. 2. 2016 pursuant to §  46 of the CAP, and, based on 
supporting documents, issues the following:  
 
 
I. 
DRAFT GENERAL MEASUR E 
number: 0111 -OOP -C070 -18 
 
laying down metrological and technical requirements for specified measuring instruments, 
including requirements for verification of the following specified instruments:  
“tendon assemblies for prestressed conc rete and rock anchors”  
 General Measure No 0111 -OOP -C070 -18 
2 1 Basic definitions  
The terms and definitions pursuant to VIM and VIML1 as well as the terms and definitions specified in 
the following shall apply for the purposes of this general measure:  
1.1 
tendon assembly  
device which serves to  prestress building structures and rock anchors using inserted reinforcement  
1.2 
stressing jack  
hydraulic cylinder with piston which serves to exert prestressing force  
1.3 
hydraulic unit  
device which serves as a source of hydraulic pressure for the stressing jack  
1.4 
force measuring instrument  
the part of a tendon assembly which serves to measure tensioning force  
1.5 
pressure gauge  
deformation or electromechanical pressure gauge used to measure the oil pressure in the stressing jack  
1.6 
reference loa d cell  
load cell which serves to verify a tendon assembly  
1.7 
reference pressure gauge  
pressure gauge which serves to calibrate the working pressure gauges of a tendon assembly  
1.8 
tendon assembly confidence interval, ENS 
The limits of the confidence inter val are given by the sum of the relative error of the force indication 
and the relative expanded uncertainty of the tendon assembly.  
1.9 
interpolated force value, Fa 
force value calculated according to the polynomial of the first, second or third degree  
1.10 
force indicated on tendon assembly scale, Fi 
the force value indicated on the scale of the tendon assembly (if the tendon assembly is equipped with 
such a scale) or the force value determined from the diagram or equation  
                                                      
1 TNI 01 0115 International Vocabulary of Metrology – Basic and General Concepts and Associated Terms 
(VIM) and International Vocabulary of Legal Metrology (VIML) are part of the technical harmonisation 
compendium ‘Terminology in the field of metrology’,  which is publicly available at www.unmz.cz.  General Measure No 0111 -OOP -C070 -18 
3 1.11 
force indicated on tendon  assembly scale, Fi 
the force value indicated on the scale of the tendon assembly (if the tendon assembly is equipped with 
such a scale) or the force value determined from the diagram or equation  
1.12 
force on one piston of a multi -cylinder tendon assembly , Fj 
the force value which one piston of the tendon assembly’s press puts on the corresponding reference 
load cell in each load level set  
1.13 
nominal test force value, FN 
the greatest force value of the tendon assembly’s measurement range  
1.14 
force value indicated on tendon assembly scale, FNS 
the force value indicated on the scale of the tendon assembly or the force value calculated from the 
pressure of the oil in the hydraulic press cylinder.  
1.15 
zero variable value before loading, I0 
indica tion value of the variable quantity (actual force or oil pressure) before a measurement series 
when the tendon assembly is unloaded, indicated in units of force or pressure  
1.16 
zero variable value after loading, If 
indication value of the variable quantit y (actual force or oil pressure) after a measurement series when 
the tendon assembly is unloaded, indicated in units of force or pressure  
1.17 
tendon assembly sensitivity coefficient, S 
The sensitivity coefficient is the ratio between the force value and t he oil pressure in the tendon 
assembly at the reference measurement point. These are usually the nominal force and oil pressure 
values.  
1.18 
expanded tendon assembly uncertainty, UNS 
the value of the error in force or oil pressure read out at each load lev el for probability P = 0.95  
1.19 
expanded relative uncertainty of tendon assembly, WNS 
the relative value of the error in force or oil pressure calculated at each load level for probability P = 
0.95 
1.20 
interpolated value of variable quantity, Fa 
force or  pressure value calculated according to the polynomial of the first, second or third degree  General Measure No 0111 -OOP -C070 -18 
4 1.21 
value of variable quantity, Xi (X1 to Xn) 
the values of the oil pressure in the cylinder of the tendon assembly (at a constant actual force) or the 
value of the actual force (at constant oil pressure in the cylinder of the tendon assembly), measured 
when verifying the tendon assembly  
1.22 
greatest value of the variable quantity at the measurement point, Xmax 
the greatest value of the variable quantity at the m easurement point in question  
1.23 
the smallest value of the variable quantity at the measurement point, Xmin 
the smallest value of the variable quantity at the measurement point in quantity  
1.24 
mean value of the variable quantity, Xr 
the value of the variable quantity (force or pressure), calculated as the arithmetic average of the values 
measured with the reference load cells or pressure gauge at each load level  
1.25 
mean value of variable specification at nominal force, XN 
mean value of variable at n ominal force. Specified in units of force or pressure.  
1.26 
relative value of the tendon assembly’s resolution, a 
relative value of the smallest specification on the tendon assembly’s force scale which can be 
indicated on the scale. It is specified in % of  the measured value (hereinafter in % MV).  
1.27 
relative repeatability error, b 
a relative value determined as the proportion of the difference of the greatest values of variable 
specifications ascertained when verifying the tendon assembly divided by thei r mean value. Expressed 
in % MV.  
1.28 
relative interpolation error, fa 
the relative value of the difference between the mean value of variable Xr and value Xa, calculated 
from the polynomial of the 1st, 2nd or 3rd degree. Expressed in % MV.  
1.29 
relative zero value error, f0 
the relative value of the difference between the values measured on the scale of the tendon assembly 
or reference load cell in relation to the nominal value. Expressed in % MV.  
1.30 
relative tendon assembly error in reverse op eration, h 
the relative value of the difference in the variable quantity (force or oil pressure) during loading and 
unloading of the tendon assembly at the same load level, in relation to the value during loading  General Measure No 0111 -OOP -C070 -18 
5 1.31 
number of tendon assembly cylinders, m 
the number of cylinders which are connected in parallel for the purpose of increasing stress force  
1.32 
number of measurement series, n 
the number of identical load cycles when verifying the tendon assembly  
1.33 
pressure value in a single cylinder of the tendon assembly, pi 
oil pressure value in a single cylinder of the tendon assembly at the applicable load level  
1.34 
nominal pressure of tendon assembly, pN 
the oil pressure in the cylinder of a stressing jack which must build up in order to reach the nomi nal 
force FN (usually the highest oil pressure value at which a test of a device for measuring the force of a 
tendon assembly is carried out). Specified in units of force or pressure.  
1.35 
average pressure value in all tendon assembly cylinders, pr 
the ave rage oil pressure value calculated from partial pressures in all tendon assembly cylinders. 
Calculated for each load level.  
1.36 
relative error of force measuring instrument, q 
the relative value of the difference in force read on the tendon assembly’s scale and the actual force, in 
relation to actual force  
1.37 
resolution capacity of tendon assembly, r 
the smallest value which the tendon assembly’s scale is capable of indicating, specified in units of 
force or oil pressure  
1.38 
standard uncertainty of interpolation, ua 
the value of the standard uncertainty of interpolation is determined as the difference in force or oil 
pressure values calculated from the interpolation scale and the actual values. Specified in units of force 
or oil pressure.  
1.39 
standard uncertainty of repeatability, ub 
the value of the standard uncertainty of repeatability is determined as the standard deviation of the 
arithmetic average of the measured values of the variable quantity (force or oil pressure)  
1.40 
combined uncertainty of the tendon assembly, uc 
The combined uncertainty of the tendon assembly is determined as the square root of the sum of the 
squares of the standard uncertainties of repeatability, resolution of the reference force and 
interpolation . General Measure No 0111 -OOP -C070 -18 
6 1.41 
standard uncertainty of zero value, u0 
The value of the standard uncertainty of the zero value is determined as the arithmetic average of the 
differences in the variable quantity after unloading and before loading the tendon assembly. Specified 
in units of force or pressure.  
1.42 
standard uncertainty of reference load cell, uEF 
The standard uncertainty of the reference load cell is calculated from the data specified on the 
calibration sheet for the reference load cells, from the environmental conditi ons and from their 
properties.  
1.43 
standard uncertainty of reference load cell calibration, uF,cal 
The standard uncertainty of the calibration of the reference load cell is calculated from the data 
specified on the calibration sheet for the reference load  cells.  
1.44 
standard uncertainty of tendon assembly resolution, ur 
The standard uncertainty of the resolution of the scale on the tendon assembly’s indication device. 
Specified in units of oil pressure or force.  
1.45 
relative standard uncertainty of interpolation, wa 
The value of the relative standard uncertainty of interpolation is determined as the difference in force 
or oil pressure values calculated from the interpolation scale and the actual values. It is in relat ion to 
the actual force value. Expressed in % MV.  
1.46 
relative standard uncertainty of repeatability, wb 
The value of the relative standard uncertainty of repeatability is determined as the standard deviation 
of the arithmetic average of the measured valu es of the variable quantity (force or oil pressure) in 
relation to the measured value at the applicable calibration point. Expressed in % MV.  
1.47 
relative standard uncertainty of calibration of reference load cell, wF,cal 
The relative standard uncertainty  of calibration of the reference load cell is calculated from the data 
specified on its calibration sheet. Expressed in % MV.  
1.48 
relative standard uncertainty of reference load cell, wEF 
The relative standard uncertainty of the reference load cell is cal culated from the data specified on the 
calibration sheet for the reference load cells, from partial relative uncertainty of environmental 
influence and from the load cells’ properties. Expressed in % MV.  
1.49 
relative standard uncertainty of zero value, w0 
The value of the relative standard uncertainty of the zero value is determined as the arithmetic average 
of the differences in the variable quantity after unloading and before loading the tendon assembly, in 
relation to the value of the variable at nomina l force. Expressed in % MV.  General Measure No 0111 -OOP -C070 -18 
7 1.50 
relative standard uncertainty of tendon assembly resolution, wr 
The relative standard uncertainty of the resolution of the scale on the tendon assembly’s indication 
device. Expressed in % MV.  
1.51 
relative uncertainty of interpolation of reference load cell, wap 
the relative uncertainty of interpolation of the reference load cell when calibrating the measuring 
instrument of the tendon assembly. It is determined from the calibration sheets of the ref erence load 
cells. Expressed in % MV.  
1.52 
relative error of reference load cell caused by signal drift, wdrift 
the relative standard uncertainty of the change in time of a reference load cell’s signal since the last 
calibration. Expressed in % MV.  
1.53 
relative error of reference load cell caused by differences in temperature, wtemp 
The relative standard uncertainty of the reference load cell caused by a temperature which was 
different when the tendon assembly was verified and when it was calibrated. Expre ssed in % MV.  
1.54 
force -pressure diagram  
the dependence of the force acting on the roving or anchor on the oil pressure in the stressing jack 
cylinder  
1.55 
measurement series  
each measurement cycle at 8 to 15 measurement points when loading the stressing jack and the 
reference load cell from the zero position to nominal force and subsequently unloading them to the 
unloaded state  
2 Metrological requirements  
2.1 Requirements for tendon assemblies  
The metrological requirements on tendon assemblies are based o n the document ETAG  0132 and are 
specified in Table  1. 
Table  1 – Metrological parameters of tendon assemblies  
Maximum 
permissible 
relative 
expansion of 
uncertainty of 
the tendon Maximum value of relative permissible error of tendon assembly for:  Maximum 
relative 
expanded 
uncertainty 
of reference 
load cell  tensioning force 
indication  tensioning force 
repeatability  tensioning force 
interpolation  resolution of 
the tendon 
assembly’s 
force indicator  
                                                      
2  ETAG  013 Post -tensioning kits for prestressing of structures. This document is available to the public at 
www.oiml.org.  General Measure No 0111 -OOP -C070 -18 
8 assembly  
WNS q b fa a WEF 
% MV  
2 ±2 1 ±1 1 0.4 
 
3 Technical requirements  
Technical requirements for tendon assemblies are divided into the following parts:  
a) stressing jack;  
b) hydraulic unit; 
c) connection hose;  
d) measuring systems;  
e) frame load plates.  
3.1 Stressing jack  
The stressing jack serves to exert and measure force when prestressing supporting elements in 
prestressed concrete structures and rock anchors. The design of the stressing jack must enable the safe 
testing of force measuring instruments (pressure and piston movement). The body of the stressing jack 
must bear a table with the basic identification information. The stressing jack may be with one 
hydraulic cylinder or several.  
Length measuring instruments which are part of certain stressing jacks are calibrated as length 
measuring instruments accord ing to separate accredited calibration procedures. Their calibration is not 
part of this general measure.  
3.2 Hydraulic unit  
The hydraulic unit serves to supply pressure oil for the stressing jack. It contains a pump with drive, 
control and measuring circu its. It also contains a cooling system for cooling the oil. The hydraulic 
unit’s pump must be dimensioned so that it is able to deliver a quantity of oil at the pressure needed to 
exert the nominal force of the stressing jack. Hydraulic unit regulation sys tems must enable the setting 
of the speed of increasing or decreasing the oil pressure in order to enable reliable indication of oil 
pressure and test force values. The hydraulic unit cabinet must bear a table with the basic 
identification information.  
3.3 Connection hose  
The connection hose must be dimensioned for the maximum possible pressure and maximum quantity 
of oil transported. The length of the hoses must conform to spatial requirements. The hoses must be 
marked with identifying information.  
3.4 Oil pressure measuring systems  
The oil pressure measuring system is mechanical or electromechanical. A mechanical measurement 
system is made up of a deformation pressure gauge. The deformation pressure gauge must have an 
accuracy of 1  % or better. An electrom echanical system is designed on the basis of tensometric or 
piezoelectric oil pressure sensors and the associated amplifiers. The uncertainty of the pressure sensors 
and amplifiers must be better than 0.2  %. The pressure sensors and amplifiers must be unam biguously 
identifiable by the manufacturer’s marks, model and serial number.  General Measure No 0111 -OOP -C070 -18 
9 3.5 Frame load plates  
The load plates are separate components of the load frame. They serve as adaptable elements for 
placing force between the reference load cells, the frame and  the stressing jack. The load plates must 
be made of material of suitable quality and workmanship. The bearing surfaces of the plates must be 
level and smooth so as not to damage the bearing surfaces of the reference load cells or tendon 
assemblies. The me asuring part of the reference load cell must be loaded by way of a ball joint. The 
plates must be dimensioned for the required load strength so as to prevent undesired deformation to 
the reference load cells which would have an adverse effect on the measur ed values.  
4 Measuring instrument markings  
4.1 Markings on tendon assemblies  
The stressing jack and hydraulic unit must bear an easily accessible manufacturer’s identification table 
with the marking:  
a) name of manufacturer or commercial company;  
b) tendon assembly model;  
c) year of manufacture;  
d) serial number;  
e) nominal force;  
f) nominal oil pressure.  
The oil pressure sensors on the stressing jack (if installed) must bear the following information:  
g) name of manufacturer or commercial company;  
h) sensor model;  
i) serial num ber; 
j) nominal pressure.  
All data, specifications, information, etc. required in the articles of this measure must be specified in 
the user manual.  
4.2 Official mark placement  
The tendon assembly must have easily accessible places to put the official marks. All measuring 
systems must have official marks in order to prevent any tampering with system elements that could 
cause changes to the measuring instrument’s metrological properties.  
5 Type approval of the measuring instrument  
5.1 General information  
The ty pe approval of the measuring instrument is not relevant.  
6 Initial verification  
6.1 General information  
The process of the initial verification of the tendon assembly encompasses:  
a) visual inspection;  
b) function test – a test of the measuring instrument’s prestressing force.  General Measure No 0111 -OOP -C070 -18 
10 6.2 Visual inspection  
The purpose of the visual inspection of the tendon assembly shall be to check that:  
a) the tendon assembly submitted for verification has all functional parts and that these parts are 
not mechanically damaged;  
b) the mea suring systems and their components are suitable in terms of functionality and integrity:  
 the stressing jack does not have a damaged piston gasket and sealing and the bearing 
surfaces and anchor elements are not damaged;  
 the pressure gauges measuring the o il pressure in the stressing jack cylinders have the 
necessary accuracy, are not damaged, do not bear signs of external intervention and operate 
smoothly;  
 the electronic indicator has the necessary accuracy (in the case of an electromechanical 
system for m easuring prestressing force);  
 the hydraulic unit has the necessary performance, does not bear signs of damage, the 
hydraulic part is well -sealed and the electrical part is free of external defects;  
 the connection hoses are correctly dimensioned for the oil  quantity and oil pressure and are 
not damaged;  
 the tendon assembly has been installed on the load frame according to the manufacturer’s 
instructions.  
6.3 Function test  
6.3.1  Test equipment  
The function test makes use of a reference load cell or set of loa d cells (depending on the type of 
tendon assembly and the size of the nominal force), a load frame, components for exerting force, a 
stressing jack, a tendon assembly measuring system, hydraulic unit and connection hose.  
6.3.1.1 General information  
Tendon assembly verification consists of the following parts:  
a) assessment of the technical condition of the tendon assembly;  
b) calibration of the prestressing force measuring system.  
6.3.1.2 Tools and equipment required  
The following measuring instruments and equipment are required for verifying tendon assemblies:  
a) reference load cells  
The test of the tendon assemblies’ force measuring instruments requires reference load cells 
with a relative expanded uncertainty less than the value specified in Table  1 of this general 
measure. The design of the reference load cell must be suitable for the verified type of tendon 
assembly.  
b) stenter frame  
The stenter frame serves to exert the test force from the stressing jack on the reference load cell. 
It must meet the technical conditions for the verification of the applicable tendon assemblies 
and must be sufficiently dimensioned so as not to affect the measurement results caused by 
uneven deformation during measuring. It is also necessary to ensure that the force and 
deformatio n influences of the frame on the verified assembly do not differ too greatly from the 
conditions during the actual prestressing. The stenter frame must be designed so as not to cause 
non-axial loading of the reference load cells or to otherwise negatively influence the results of 
the tendon assembly measuring instrument test.  
c) pressure gauges for tendon assembly calibration  General Measure No 0111 -OOP -C070 -18 
11 The tendon assembly must be fitted with pressure gauges of a suitable design and corresponding 
precision class. Tendon assembly verifica tion can be carried out with a reference pressure gauge 
which is not part of the tendon assembly. In this case, the tendon assembly must be 
supplemented by additional pressure gauges of the required precision class with valid 
calibration sheets. It will th en be necessary to correct the uncertainty of the tendon assembly by 
the calibration uncertainty of these pressure gauges.  
Components of the stenter frame include other auxiliary devices which serve to manipulate the 
stressing jack and reference load cell and fit them into the frame. Base plates for exerting force 
on the reference load cell, stressing jack and clamping parts are also part of the frame.  
d) thermometer for measuring the ambient temperature  
Thermometers serve to measure the temperature of the environment during measuring, for 
measuring the temperature of the reference load cells and for measuring the oil temperature. The 
maximum permissible error of thermometers for measuring the ambient temperature and load 
cells is ±0.6  °C. 
6.3.2 Performance of the function test  
The tendon assembly is fitted with a built -in reference load cell (or load cells) for the test of the 
prestressing force measuring system. Setup and connection are checked and the hydraulic unit is 
turned on. The system is left at rest  for 30 minutes to allow the operation and electronic measuring 
system of the force gauges to stabilise. The zero value of the force and oil pressure are then detached 
and a load cycle is conducted from an unloaded state to the nominal force value of the t endon 
assembly (usually the upper limit of the measurement range). The force is maintained at this value for 
a period of 3  minutes. The smoothness of the increase in load force and the behaviour of the stressing 
jack are checked during loading. If there is  a delay at nominal force, then the stability of maintaining 
the set force is to be checked. If this function test is carried out without problems, then the test of the 
tendon assembly’s load cell equipment is conducted according to point  6.3.3.  
6.3.3 Test  of the tendon assembly’s force measuring instrument  
This test is conducted by one of two measurement procedures. Each procedure begins with three 
preliminary loadings from the unloaded state to the nominal force value of the tendon assembly and 
then by un loading it to the unloaded state. The delay at zero force value and nominal value is greater 
than 90  seconds. The value of the force and pressure in the unloaded state and at nominal prestressing 
force value is recorded during this process. Once the prelim inary loading has been completed, the 
actual measuring cycle is carried out.  
With tendon assemblies having one hydraulic cylinder, at least three measurement series are 
conducted under loading with removal of actual force and pressure values at the force c alibration 
points with subsequent unloading from the upper limit of the measurement range to the unloaded state. 
The measurement series must contain at least eight load levels.  
With tendon assemblies having two or more cylinders, the reference load cell is  placed beneath each 
piston of the tendon assembly. Preliminary loading to the maximum loading force with subsequent 
complete unloading is carried out three times. The delay upon preliminary loading at zero value must 
be longer than 30  seconds. Two measure ment series are then carried out under loading with removal 
of the actual force values beneath each cylinder of the stressing jack and the oil pressure values in each 
cylinder of the stressing jack or average oil pressure in all cylinders. The measurement is carried out at 
each load level up to nominal force. It is then unloaded to the unloaded state. If the tendon assembly 
allows, then two measurement series are to follow during loading and unloading (series  3 and 4) while 
removing the actual force and oil  pressure values at the measurement points. If the tendon assembly 
does not allow a test to be carried out in reverse operation, then one measurement series is to follow 
under unloading only.  
Each measurement series must contain at least eight points on th e tendon assembly’s force scale. The 
individual measurement errors may not be greater than the values specified in Table  1. General Measure No 0111 -OOP -C070 -18 
12 6.4 Evaluation of the test of tendon assemblies with one cylinder  
The values measured during the accuracy test are recorded and eval uated.  
6.4.1 Mean value of the variable quantity  
The mean value of the variable quantity is calculated from the values removed in the first, second and 
final measurement series ( X1 to Xn) during loading. The calculation is conducted according to the 
equation:  

n
ii r XnX
11
  (1) 
6.4.2 Tendon assembly sensitivity coefficient  
The sensitivity coefficient of the tendon assembly is determined as a proportion of the actual force and 
the corresponding oil pressure at the value of the upper limit of t he tendon assembly’s measurement 
range. The calculation is conducted according to the equation:  
NN
pFS
  (2) 
If the force is the constant quantity during the measurement, then the maximum force of the measured 
range (in units of force) is se t for FN and the mean pressure value Xr (in units of pressure) is set for pN. 
If oil pressure is the constant quantity during the measurement, then the mean value Xr (in units of 
force) is set for the force value FN and the corresponding pressure value is set for pN (in units of 
pressure).  
6.4.3 Relative error of force measuring instrument  
The relative error of the force measuring instrument q is determined as the difference between the 
force value Fi measured by the tendon assembly and the corresponding mean actual force value Fr. 
The value Fi is the force indicated by the tendon assembly (if the tendon assembly has a readout in 
units of force) or the force is calculated from the pressure values by me ans of the sensitivity 
coefficient. This error is only indicated if the sensitivity coefficient is the output value of the tendon 
assembly measuring instrument test or if the tendon assembly has a scale in units of force. In the case 
of tendon assemblies w ith a scale in units of pressure with readout of force -pressure values in the table 
and diagram, then this error is not indicated. The relative error q is specified in per  cent of the 
measured value (% MV) and is determined according to the equation:  
100
rr i
FFFq
  (3) 
in which  Fi  ....  is the force indicated by the tendon assembly (kN, MN)  
 Fr  ....  is the actual force value measured by the reference load cell (kN, MN).  
6.4.4 Relative repeatability error of the force measuring instrument  
The relative  repeatability error b is determined from the values measured during the test of the tendon 
assembly. It is expressed in % MV and determined from the equation:  
100m in m ax
rXX Xb
  (4) 
in which  b ......  is the relative repeatability error of the tendon asse mbly (% MV),  General Measure No 0111 -OOP -C070 -18 
13  Xmax  .  is the maximum force or oil pressure value indicated by the tendon assembly 
(depending on which quantity is variable) for the load level in question (kPa, MPa, 
bar or kN, MN),  
 Xmin  .  is the minimum force or oil pressure value indicated by the tendon assembly 
(depending on which quantity is variable) for the load level in question (kPa, MPa, 
bar or kN, MN).  
  Xr .....  value of the variable quantity (force or pressure), calculated as the arithmetic average 
of the values measured with the reference load cells or pressure gauge at each load 
level (kPa, MPa, bar or kN, MN).  
6.4.5 Relative resolution error of indicator devi ce 
The relative resolution error of indicator device a is determined from the indicator’s resolution value r 
and the force value F for each measurement point. It is specified in % MV and determined from the 
following equation:  
𝑎=𝑟
𝐹𝑖×100  (5) 
in which  a  ..  is the relative resolution error (% MV),  
 r  ...  is the resolution value of the tendon assembly’s scale (kN, MN),  
 Fi  ..  is the value of the load level (kN, MN).  
6.4.6 Relative interpolation error of the force measuring instrument  
The relative interpolatio n error fa is determined for each measured value of force as the difference 
between the force value measured by the tendon assembly and the value calculated from the 
polynomial of the first, second or third degree  or read from the diagram. The relative interpolation 
error fa is expressed in % MV. It is calculated from the equation:  
100
rr a
aFF Ff
  (6) 
in which  fa  .....  is the relative interpolation error (% MV),  
 Fr  ....  is the calculated mean value of the actual force (oil pressure is the constant quantity) 
(kN, MN),  
 Fa  ....  is the force value calculated according to the polynomial of the first, second or third 
degree (kN, MN).  
6.5 Test of tendon assemblies with stressing jack with multiple cylinders  
Proceed accordingly when verifying tendon assemblies with a stressing jack with multiple cylinders. 
The test is conducted at constant oil pressure at the load level. The values measured during the test are 
recorded and evaluate d. This procedure applies to tendon assemblies with m measuring cylinders, in 
which each cylinder has an electromechanical pressure gauge and pressure oil intake of its own. The 
test force is measured with a separate load cell for each measuring piston of the stressing jack. The 
reference load cells must be conducted to a measuring system with m components. The measured force 
values must be removed from all reference load cells at the same moment in time.  
6.5.1 Mean oil pressure value in the cylinders of th e stressing jack  
The oil pressure in each cylinder is measured with a separate electromechanical pressure gauge. The 
mean pressure value is calculated from the pressure values measured and serves as the constant value 
for measuring the actual forces which the pistons of the tendon assembly exert upon the reference load 
cells.  General Measure No 0111 -OOP -C070 -18 
14 

m
ii r pmp
11  (7) 
6.5.2 Value of the test force of the tendon assembly at load level for the measurement series  
The total force development by the tendon assembly at the load  level in question is calculated from the 
values measured by the reference load cells. The calculation is conducted according to the equation:  

m
jj i F F
1
  (8) 
6.5.3 Mean value of the test force of the tendon assembly at load level  
The average value of the tendon assembly’s prestressing force is determined from the values measured 
by the reference load cells at the point in question. The calculation is conducted according to the 
equation:  

n
ii r FnF
11
  (9) 
6.5.4 Tendon assembly sensiti vity coefficient  
The sensitivity coefficient of the tendon assembly is determined as a proportion of the actual force and 
the corresponding oil pressure at the point on the tendon assembly’s measurement range which serves 
to set the characteristics. The ca lculation is conducted according to the equation:  
rr
pFS
  (10) 
6.5.5 Force indicated by tendon assembly  
The force indicated by the tendon assembly is determined by two methods. In tendon assemblies 
equipped with a scale in units of force, t his value of force is read on the scale. In tendon assemblies 
equipped with a pressure gauge with a scale in units of pressure, the force is calculated from the 
equation:  
r NS pS F
  (11) 
6.5.6 Relative error of force measuring instrument  
The relative error of the force measuring instrument q is determined as the difference between the 
force value Fi measured by the tendon assembly and the corresponding actual force value Fr. The 
value Fi is the force indicated by the tendon assembly (if th e tendon assembly has a readout in units of 
force) or the force is calculated from the pressure values by means of the sensitivity coefficient. This 
error is only indicated if the sensitivity coefficient is the output value of the verification of the tendo n 
assembly or if the tendon assembly has a scale in units of force. In the case of tendon assemblies with 
a scale in units of pressure with readout of force -pressure values in the table and diagram, then this 
error is not indicated. The relative error q is specified in per  cent of the measured value (% MV) and is 
determined according to the equation:  
100
rr i
FFFq
 (12) 
in which  Fi  ....  is the force indicated by the tendon assembly (kN, MN),  
 Fr  ....  is the actual force of the tendon assembly measured by the reference load cells (kN, 
MN).  General Measure No 0111 -OOP -C070 -18 
15 6.5.7 Relative repeatability error of the force measuring instrument  
The relative repeatability error b is determined from the values measured during the test of the  tendon 
assembly. It is calculated from the equation:  
100m in m ax
rXX Xb
 (13) 
in which  b ......  is the relative repeatability error of the tendon assembly (% MV)  
 Xmax  .  is the maximum value of force indicated by the tendon assembly at the load level (kN, 
MN),  
 Xmin  .  is the minimum value of force indicated by the tendon assembly at the load level (kN, 
MN),  
 Xr  ....  is the mean value of the variable quantity (force) at the l oad level in question (kN, 
MN).  
6.5.8 Relative resolution error of indicator device  
The relative resolution error of indicator device a is determined from the indicator’s resolution value r 
and the force value Fr for each load level. It is specified in % M V and determined from the following 
equation:  
100
rFra
  (14) 
6.5.9 Relative error of the zero value of the tendon assembly’s force measuring instrument  
The relative error of the error value f0 is determined as the average of the difference in values of the 
variable quantity measured prior to loading and after unloading. This test is only carried out if the 
tendon assembly enables controlled continuous unloading all the way to a completely unloa ded state. 
The error value f0 is expressed in % MV. It is calculated from the equation:  
1000
0 
Nf
XIIf
  (15) 
in which   f0  ....  is the relative error of the zero value (% MV),  
 If  .....  is the specification of the tendon assembly after unloading (kN, MN),  
 I0  .....  is the specification of the tendon assembly prior to loading (kN, MN),  
 XN  ...  is the specification of the tendon assembly at nominal force (kN, MN).  
6.5.10 Relative error of force measuring instrument in reverse operation  
The relative reverse operatio n error h is determined as the average of the difference in variable 
quantity values measured during loading and unloading. The values measured in the third and fourth 
measurement series are used for the calculation ( X3, X´3, X4, X´4). Expressed in % MV. I t is calculated 
according to the equation:  
ℎ=|(𝑋´3−𝑋3)+(𝑋´4−𝑋4)
𝑋3+𝑋4|×100  (16) 
in which  h ......  is the relative reverse operation error of the tendon assembly (% MH),  
 X´3  ..  is the value of force measured during unloading after the third measurement series 
(kN, MN),  General Measure No 0111 -OOP -C070 -18 
16  X3  ....  is the value of force measured during loading in the third measurement series (kN, 
MN),  
 X´4  ..  is the value of force measured during unloading after the fou rth measurement series 
(kN, MN),  
 X4  ....  is the value of force measured during loading in the fourth measurement series (kN, 
MN).  
6.6 Measurement uncertainty calculation  
6.6.1 Source of uncertainties during measurement  
The standard measurement uncertainties are determined according to the information specified in 
Table  2. 
Table  2 – Sources of standard uncertainties  
Source of 
uncertainty  Distribution and 
type of standard 
uncertainty  Standard uncertainty  Relative standard uncertainty  
Repeatability of 
measured values  Normal distribution  
Uncertainty type A  

12
1



nnFF
un
ir i
b  

11002


nnFF
Fwr i
stb  
Interpolation  Isosceles triangle 
distribution  
Uncertainty type B  
aa
a Ffu100 
a af w  
Zero value  Right -angle 
distribution  
Uncertainty type B  
10030
0NF fu 
30
0fw  
Resolution 
capacity of 
tendon assembly  Right -angle 
distribution  
Uncertainty type B  
6rur 
6awr  
Force gauge  Normal distribution  
Uncertainty type A  
100 2,
,i calEF
calFF Wu  
2,
,calF
calFWw  
Pressure gauge  Normal distribution  
Uncertainty type A  
2Ep
EpUu 
2Ep
EpWw  
Working 
pressure gauge 
of tendon 
assembly  Normal distribution  
Uncertainty type A  
2pp
ppUu 
2pp
ppWw  
6.6.2 Combined uncertainty  General Measure No 0111 -OOP -C070 -18 
17 The relative combined uncertainty is calculated as the square root of the sum of the squares of the 
standard uncertainties.  
The standard uncertainty of reference load cells is determined from the equation:  
2 2 2 2
, ap drift temp calF EF w w w w w 
  (17) 
in which  wF,cal  is the relative standard uncertainty of the reference load cell calculated from the data 
from its calibration sheet (% MV),  
  wtemp  relative standard uncertainty of the reference load cell caused by a temperature which 
was different when the tendon assembly was verified from when it was calibrated (% 
MV),  
  wdrift  relative standard uncertainty of the change in time of reference load cells’ signal 
since the last calibration (% MV),  
  wap  relative uncertainty of interpolatio n of the reference load cell when calibrating the 
measuring instrument of the tendon assembly. It is determined from the calibration 
sheets of the reference load cells (% MV).  
For single -cylinder tendon assembly  
2 2 2
EF r b c u u u u 
 (18) 
2 2 2
EF r b c w w w w 
 (19) 
For multi -cylinder tendon assembly  
2 2 2
02 2
EF a r b c w uuuu u 
 (20) 
2 2 2
02 2
EF a r b c w w w w w w 
  (21) 
6.6.3 Relative expanded measurement uncertainty  
The relative expanded measurement uncertainty of a tendon assembly is obtained by multiplying the 
combined uncertainty of the measurement coefficient of expansion k. For tendon assemblies, the 
probability is assumed to be P = 0.95. This results in a coeffi cient of expansion k = 2. The relative 
expanded uncertainty of the tendon assembly is calculated from the equation:  
c NS u U2
  (22) 
c NS w W2
 (23) 
The resulting expanded uncertainty value is specified with an accuracy of two digit s. 
6.6.4 Tendon assembly confidence interval  
The boundaries of the tendon assembly confidence interval ENS are given by the sum of the relative 
indication error and the relative expanded measurement uncertainty. It is specified in % MV and 
determined from the following equation:  
NS NS Wq E
  (24) 
The confidence interval is specified in the tendon assembly’s verification sheet.  General Measure No 0111 -OOP -C070 -18 
18 7 Follow -up verification  
7.1 General information  
The process of the follow -up verification of the tendon assembly encompasses the following tests:  
a) visual inspection;  
b) force measuring instrument test.  
7.2 Visual inspection  
The visual inspection in the follow -up verification is carried out according to Article  6.2. 
7.3 Function tests  
7.3.1  Test equipment  
The equipment pursuant to Article  6.3.1 is used for the tests.  
7.3.2 Performance of the function test  
The function test is performed according to Article  6.3.2.  
In case of any faults, the measuring instrument shall be disqualified from further tests.  
7.3.3 Test of the t endon assembly’s force measuring instrument  
The test of the measuring instrument’s accuracy is performed according to Article  6.3.3.  
The measurement errors may not be greater than the values specified in Table  1. 
7.4 Evaluation of force measuring instrumen t test  
The test is evaluated by conducting the procedure specified in Articles  6.4 and 6.5.  
8 Measuring instrument examination  
When examining measuring instruments pursuant to §  11a of the Metrology Act at the request of a 
person who may be affected by an incorrect measuring instrument, please proceed according to 
Chapter  7. 
9 Notified standards  
For the purposes of specifying the metrological and technical requirements for measuring instruments 
and specifying the testing methods for their type approval and verification arising from this general 
measure, the CMI shall provide notification of the Cz ech technical standards, other technical standards 
or technical documents of international or foreign organisations, or other technical documents 
containing more detailed technical requirements (hereinafter notified standards). The CMI shall 
publish a list  of these notified standards attached to the relevant measures, together with the general 
measure, in a manner accessible to the public (on www.cmi.cz ). 
Compliance with notified standards or parts thereof is considered , to the extent and under the 
conditions stipulated by a general measure, to be compliance with the requirements stipulated by this 
measure to which these standards or parts thereof apply.  
Compliance with notified standards is one way of demonstrating comp liance with the requirements. 
These requirements may also be met by using another technical solution guaranteeing an equivalent or 
higher level of protection of legitimate interests.  General Measure No 0111 -OOP -C070 -18 
19  
II. 
G R O U N D S 
The CMI issues, pursuant to §  14(1)(j) of the Metrolog y Act, for the implementation §  6(2), §  9(1) and 
(9) as well as §  11a(3) of the Metrology Act, this general measure, stipulating metrological and 
technical requirements for specified measuring instruments and requirements for verification of these 
specifie d measuring instruments – ‘tendon assemblies for prestressed concrete and rock anchors’.  
Decree No  345/2002 laying down measurement instruments for mandatory validation and 
measurement instruments subject to type approval, as amended, classifies the measur ing instruments 
under item  2.4.1 in the annex to the Second List of Specified Measurement Instruments of the 
specified type as measurement instruments subject to type approval and mandatory validation.  
This legislation ( general measure) will be notified in  accordance with Directive (EU)  2015/1535 of the 
European Parliament and of the Council of 9  September  2015, laying down a procedure for the 
provision of information in the field of technical regulations and of rules on Information Society 
services.  
 
III. 
I N S T R U C T I O N S 
In accordance with §  172(l) APC, in conjunction with §  39(l) APC, the CMI has stipulated a time limit 
for comments of 30  days as of the date of posting on the official notice board. Comments submitted 
after this time will not be con sidered.  
The persons concerned are hereby invited to comment on this draft general measure. In light of the 
provisions of §  172(4) of the APC, comments shall be submitted in written form.  
In accordance with the provisions of §  174(l) APC in conjunction wit h § 37(l) APC, it must be clear 
who is making the comments, which general measure they address, how it contradicts legislation or 
how the general measure is inaccurate, and the signature of the person making the comment must be 
included.  
The supporting doc uments for this draft measure of a general nature may be consulted at the Czech 
Metrological Institute, Department of Legal Metrology, Okružní 31, 638 00 Brno, upon appointment 
by telephone.  
This general measure shall be posted for 15  days.  
 
 
 
 
 ...…………………………..............  
RNDr. Pavel Klenovský  
Director -General  
 
 
Person responsible for accuracy: Mgr. Tomáš Hendrych  
 General Measure No 0111 -OOP -C070 -18 
20 Posted on:  
Signature of the authorised person confirming posting:  ....................................................  
 
Removed on:  
Signature of the authorised person confirming removal:  ....................................................