T aceable To que Measu emen unde
Ro a ion in Nacelle Tes Benches
– A Good P ac ice Guide –
Paula Weidinge
Gisa Foye
Physikalisch-Technische Bundesans al (PTB), 2019
2 DOI: h ps://doi.o g/10.7795/530.20190111
This guide has been p oduced wi hin he EURAMET p ojec en i led To que Measu emen in he MN m
1
ange. Mo e in o ma ion abou his collabo a i e esea ch p ojec can be ound on he p ojec ’s websi e
h ps://www.p b.de/em p/ind14-home.h ml. The aim o his guide is o p o ide p ac ical in o ma ion and
ad ice abou o que measu emen and especially abou o que calib a ion in nacelle es benches o
nacelle es bench ope a o s.
Disclaime
Any men ion o comme cial p oduc s wi hin his guide is o in o ma ion only; i does no imply
ecommenda ion o endo semen by he pa ne s in his p ojec .
The iews exp essed in his guide a e hose o he au ho s and o he EMPIR 14IND14 p ojec eam.
Acknowledgemen o unding
The p oduc ion o his guide was unded by he Eu opean Me ology P og amme o Inno a ion and
Resea ch (EMPIR). The EMPIR ini ia i e is co- unded by he Eu opean Union’s Ho izon 2020 esea ch
and inno a ion p og amme and he EMPIR Pa icipa ing S a es.
Au ho ship
P epa a ion o his guide was led by Paula Weidinge and Gisa Foye o he Physikalisch-Technische
Bundesans al (PTB), B aunschweig (Ge many) wi h ex ensi e inpu om all membe s o he EMPIR
14IND14 p ojec eam. The discussion and inpu o all he pa ne s in he p ojec and hei colleagues
a e g ea ly app ecia ed.
Sugges ion o he quo a ion o he e e ences
Weidinge , Paula and Foye , Gisa, 2019. T aceable To que Measu emen unde Ro a ion in Nacelle
Tes Benches: A Good P ac ice Guide. Physikalisch-Technische Bundesans al (PTB).
DOI: h ps://doi.o g/10.7795/530.20190111
This documen and all pa s con ained he ein a e p o ec ed by copy igh and a e subjec o he C ea i e
Commons use license CC by 4.0 (h ps://c ea i ecommons.o g/licenses/by/4.0/).
P ojec logo
All copy igh and ela ed o neighbou ing igh s o his logo a e wai ed using he CC0 Public Domain
Dedica ion (h ps://c ea i ecommons.o g/publicdomain/ze o/1.0/).
DOI: h ps://doi.o g/10.7795/920.20190111
1
The uni o o que can also be w i en as MN·m.
14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide
DOI: h ps://doi.o g/10.7795/530.20190111 3
Con en s
1 In oduc ion 4
1.1 Glossa y 4
1.2 Symbols and hei meaning 4
2 Calib a ion se -up 6
2.1 Place o measu e he e e ence o que 6
2.2 To que ans e s anda d 6
2.3 Da a acquisi ion 7
2.3.1 Ampli ie and il e se ings 7
2.3.2 Timewise synch onisa ion o di e en da a se s 7
2.4 Example o a se -up 8
3 Pe o ming a o que calib a ion 11
3.1 P epa a o y ope a ions and es s 11
3.2 Ambien and bounda y condi ions 12
3.3 Signal e alua ion 13
3.4 De e mina ion o he ze o signal 13
3.4.1 S a ic ze o-poin de e mina ion 14
3.4.2 Ro a ional ze o-poin de e mina ion 14
3.5 Quasi-s a ic o que calib a ion 15
3.6 Cha ac e isa ion maps 15
3.7 C oss alk e ec s 17
3.8 Calib a ion in e al 18
4 E alua ion o he calib a ion esul including a measu emen unce ain y 19
4.1 E alua ion o he ansduce o be calib a ed 19
4.1.1 Rela i e indica ion de ia ion 19
4.1.2 Rela i e epea abili y 20
4.1.3 Rela i e esolu ion 20
4.1.4 Rela i e e e sibili y 21
4.2 Measu emen unce ain y 21
4.2.1 Measu emen condi ions 21
4.2.2 Unce ain y con ibu ion o he esolu ion 22
4.2.3 Unce ain y con ibu ion o he epea abili y 22
4.2.4 Unce ain y con ibu ion o he ans e s anda d 23
4.2.5 Expec ed alue o he indica ion de ia ion 23
4.2.6 Example o an unce ain y calcula ion 23
5 Calib a ion ou pu and bene i o he es bench ope a o 24
Glossa y 25
6 Re e ences 26
4 DOI: h ps://doi.o g/10.7795/530.20190111
1 In oduc ion
P io o he ma ke launch o wind u bines (also called nacelles), la ge gea boxes and gene a o s,
ex ensi e es s, which can be pe o med on a nacelle es bench, a e o g ea impo ance. One such
es is he e iciency de e mina ion o he de ice unde es . Fo di ec e iciency de e mina ion, he
mechanical inpu di ec ly a he lange o he de ice unde es and he elec ical o mechanical ou pu
o he de ice unde es a e o be measu ed. While he ou pu can al eady be measu ed wi h a su icien
unce ain y, measu ing he inpu consis ing o o que and o a ional speed poses a p oblem. A b oad
a ie y o measu ing ins umen s is a ailable o measu ing o a ional speeds. The o que ha appea s
in nacelle es benches, howe e , anges up o se e al MN m and canno easily be de e mined due o
he lack o aceabili y possibili ies. This good p ac ice guide in oduces a me hod o acing la ge o que
measu emen up o 5 MN m in nacelle es benches using a o que ans e s anda d.
This good p ac ice guide comp ises he ollowing sec ions. A lis o he gene al equi emen s on he
pe o mance o a o que calib a ion in nacelle es benches including he calib a ion se -up is gi en in
sec ion 2. A desc ip ion o he p epa a o y wo k, es s and ins uc ions on a quasi-s a ic o que
calib a ion and a o que calib a ion using so-called cha ac e isa ion maps o co e he en i e ope a ion
ange o a nacelle es bench as pa o he pe o mance o a o que calib a ion a e ou lined in sec ion 3.
Guidelines o he e alua ion o he calib a ion esul s including he de e mina ion o a measu emen
unce ain y a e in oduced in sec ion 4. Sec ion 5 again s a es he bene i s o aceable o que
measu emen in nacelle es benches o he ope a o s o he es benches and he easibili y o he
calib a ion esul s.
Fu he in o ma ion abou unde s anding measu emen and measu emen unce ain y can be ound in
he Guide o he exp ession o unce ain y in measu emen (GUM) [7] and he In e na ional Vocabula y
o Me ology (VIM) [5]. Gene al in o ma ion abou ope a ing p ocedu es in calib a ion labo a o ies is
gi en in DIN 17025 [2], while in o ma ion abou s a ic o que calib a ion can be aken om
EURAMET cg-14 [6], one o he Eu opean calib a ion guidelines.
1.1 Glossa y
We ha e p o ided a glossa y o echnical e ms ha a ise in he ollowing desc ip ion o a o que
calib a ion in nacelle es benches a he end o his documen .
1.2 Symbols and hei meaning
Impo an symbols and hei meaning ega ding o que calib a ion in nacelle es benches a e lis ed in
Table 1.
Table 1 Symbols and hei meaning.
Symbol
Uni
Meaning
a
%
Rela i e esolu ion o he o que measu ing ins umen in he es bench
aF
%
Rela i e esolu ion o he o que measu ing ins umen in he es bench unde
load
aZ
%
Rela i e esolu ion o he o que measu ing ins umen in he es bench a e
load elease
b
%
Rela i e epea abili y o he o que measu ing ins umen in he es bench
sample
Hz
Sampling equency o he DAQ
HNTB/TTS
% H
Rela i e humidi y measu ed close o he o que measu emen ins umen in he
es bench (NTB) and close o he o que ans e s anda d (TTS)
k
-
Ampli ica ion ac o o calcula e he expanded unce ain y based on he
combined unce ain y
l
-
In ege numbe o e olu ions ha a e a e aged o e
M
kN m
Inc easing o que load indica ed by he o que ans e s anda d
M'
kN m
Dec easing o que load indica ed by he o que ans e s anda d
Mi
kN m
Inc easing o que load indica ed by he o que measu ing ins umen in he es
bench
14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide
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Mi
'
kN m
Dec easing o que load indica ed by he o que load in he es bench
Mi



,M

kN m
A i hme ic mean o se e al measu emen s o Mi and M a he same load s ep
Mi,0
kN m
Residue indica ion o he o que measu emen ins umen in he es bench a e
load elease
ML
kN m
To que load s ep
nmax
min-1
Maximum o a ional speed o he es bench conside ing he de ice unde es
nNTB
min-1
Ro a ional speed measu ed in he es bench
n
NTB
min-1
A i hme ic mean o he measu emen o o a ional speed
q

%
Rela i e indica ion de ia ion o he o que measu ing ins umen in he es bench
a e aged o e se e al epe i ions
q
j
%
Rela i e indica ion de ia ion o he o que measu ing ins umen in he es bench
pe load cycle
qmax
%
Maximum alue o q a each load s ep
qmin
%
Minimum alue o q a each load s ep
kN m
Resolu ion o he o que measu ing ins umen in he es bench
o
°
En isioned signal esolu ion pe o a ion
S
mV/V
Measu emen signal
Sze o. o
mV/V
Ro a ional o que ze o signal
Sze o,s a
mV/V
S a ic o que ze o signal
dwell
s
Dwell ime be o e measu emen
hea
s
Time o hea up all componen s un il s able condi ions a e eached
meas
s
Measu emen ime depending on he minimum o a ional speed and he numbe
o e olu ions ha a e a e aged o e
amp
s
Time o amp up o down o que o o a ional speed
s ep
s
To al measu emen ime pe o que s ep
uc
%
Combined absolu e measu emen unce ain y
ui
%
Unce ain y componen
u ep
%
Unce ain y componen due o he epea abili y
u es
%
Unce ain y componen due o he esolu ion
us d
%
Unce ain y componen due o he deployed o que ans e s anda d
U
%
Expanded absolu e measu emen unce ain y
%
Rela i e e e sibili y o he o que ansduce in he es bench
ϑNTB/TTS
°C
Tempe a u e measu ed close o he o que measu emen ins umen in he es
bench (NTB) and close o he o que ans e s anda d (TTS)

6 DOI: h ps://doi.o g/10.7795/530.20190111
2 Calib a ion se -up
Due o se e al cons ain s on nacelle es benches, he ope a o s use di e en me hods in di e en
places o measu e he inpu o que o he de ice unde es . An example o a nacelle es bench including
he possible posi ions o measu ing o que is depic ed in Figu e 1.
In nacelles, he main axis is he x-axis. Consequen ly, he main o que measu ed in nacelle es benches
is Mx. Al hough he main axis o o que measu emen in me ology is he z-axis, in he ollowing
desc ip ion and ins uc ions, he main axis is he x-axis and he main o que o be measu ed is Mx since
his good p ac ice guide is di ec ed a es bench ope a o s.
Figu e 1 Examples o o que measu emen op ions in es benches and he coo dina e sys em o a nacelle and,
he e o e, he es bench [9].
2.1 Place o measu e he e e ence o que
To de e mine he e iciency o a de ice unde es using he di ec measu emen me hod by de e mining
he inpu and ou pu o he de ice unde es , he o que should ideally be measu ed di ec ly a he
connec ion lange be ween he es bench and he de ice unde es . In mos es benches, specially
designed adap e s a e equi ed o ins all his addi ional o que ansduce o measu e he e e ence
o que. A calib a ion o he es bench is no possible wi hou a de ice unde es , because only hen is
a o que gene a ion possible. Fo a calib a ion o he ypical es ing ange ( o que and o a ional speed)
o he es bench, a sui able es objec ep esen ing equen ly es ed objec s is o be ins alled on he
es bench. Ideally, his es objec p o ides ull access o i s con ol sys em o allow he ini ia ion o
se e al con ol scena ios dependen on he con olled change o elec ical b aking powe asse ed by
he gene a o .
All o que ansduce s, he e e ence o que ansduce as well as he o que ansduce in he es
bench, mus be aligned e y p ecisely o minimise pa asi ic pe manen loads such as longi udinal and
la e al o ces (Fx, Fy and Fz) and bending momen s (My and Mz) on he o que ansduce . Possible
misalignmen s a e caused by a lack o plana i y on he adap e s, a lack o concen ici y o he en i e
d i e ain, and a w ong dis ance be ween he load applica ion sys em and he de ice unde es .
2.2 To que ans e s anda d
Fo measu ing he e e ence o que, o which he o que measu emen in a es bench is hen compa ed,
a so-called o que ans e s anda d is needed. A ans e s anda d is a measu emen gauge ha bea s
a de ined ela ion be ween a physical quan i y, which in his case is o que, and a uni o measu emen ,
he e kN m. This o que ans e s anda d is o be calib a ed acco ding o EURAMET cg-14 [6], a
Eu opean calib a ion guide o DIN 51309 [3], he Ge man o que s anda d.
A o que ans e s anda d has o mee se e al equi emen s. Fi s , he ans e s anda d mus ha e a
su icien measu emen ange o co e he ope a ional o que ange o he es bench, and i is o be
calib a ed o e his measu emen ange. The bes physical p inciple wo king in he MN m o que ange
is he de ec ion o s ains by means o al e na ing elec ical esis ance using s ain gauges. The s ain
gauges a e glued o a de o ma ion body made o s eel. To gain he equi ed s i ness o he ans e
P ime mo e Load applica ion
sys em Main gea box Gene a o
(load machine)
De ice unde es
To que based
on elec ical
powe and
o a ional speed
To que based on
elec ical powe
and o a ional
speed
To que on
low speed
sha
To que on low
speed sha
wi h addi ional
loads
To que on
high speed
sha
z
y
x
14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide
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s anda d’s de o ma ion body and a su icien sensi i i y a he same ime, a hollow sha - ype
de o ma ion body is bes (p ojec esul aken om [10]).
Mo eo e , he ans e s anda d mus wi hs and he occasionally occu ing addi ional mechanical loads
c ea ed by he load applica ion sys em as i is ins alled di ec ly a he hub lange o he de ice unde es
and is, he e o e, exposed o all simula ed wind loads caused by he load applica ion sys em. E en when
no explici addi ional loads a e applied o he d i e ain, he load applica ion sys em deploys loads o
s abilise he d i e ain, leading o powe losses and addi ional ic ion o que along he d i e ain du ing
o a ion. Fo in o ma ion abou hese addi ional loads and o su eillance easons, he ans e s anda d
should be equipped wi h addi ional measu ing b idges o sense bending momen s, and longi udinal and
la e al o ces. Addi ional knowledge abou he beha iou o he ans e s anda d unde al e na ing
empe a u e (and humidi y) is ad an ageous, since he ambien condi ions in a es bench do no comply
wi h he labo a o y condi ions du ing he calib a ion o he ans e s anda d.
In gene al, he ans e s anda d has o mee special equi emen s ega ding i s dimensions and weigh .
These equi emen s a e no only limi ed by he es benches, bu also by he a ailable o que calib a ion
machine ha is used o cha ac e ise he o que ansduce and lead o i being a ans e s anda d. In
o de o induce he o que load up o se e al MN m co ec ly and o ensu e he easy moun ing o he
ans e s anda d, a lange wi h bo e holes o bol s is an app op ia e ype o connec ion. As men ioned
abo e, his migh call o specially designed adap e s o ins all he ans e s anda d in he es bench.
2.3 Da a acquisi ion
A imewise synch onised da a eco ding o he o que measu ed by he ansduce o he es bench and
by he ans e s anda d can be ealised ei he by one sha ed o by wo synch onised da a acquisi ion
sys ems.
Rega dless o he da a acquisi ion sys em used, all eco ded da a should be imes amped, and bo h he
s a and end ime o he measu emen a e o be documen ed. O he han o s a ic calib a ions, he
signals a e o be eco ded con inuously o enable an in es iga ion o he angula accele a ion and i s
impac on he o que signals. The quan i ies o be measu ed du ing a calib a ion a e lis ed in Table 2.
Table 2 Quan i ies o be measu ed o a o que calib a ion in es benches.
Quan i y o be measu ed
Symbol
Reading
Uni
To que measu ed by he ansduce in he es bench
Mi
mV/V
kN m
Ro a ional speed measu ed by ins umen s in he es bench o he TTS
nNTB
V
min-1
To que measu ed by he ans e s anda d
M
mV/V
kN m
Tempe a u e measu emen close o he es bench ansduce and he
ans e s anda d ( emp. meas. inside he ans e s anda d)
ϑNTB,
ϑTTS
V
°C
Humidi y measu emen close o he es bench ansduce and he
ans e s anda d (humid. meas. inside he ans e s anda d)
HNTB,
HTTS
V
% H
Tempe a u e ϑ and humidi y H a e o be measu ed as close o bo h o que ansduce s as possible.
Ideally, empe a u e and humidi y a e measu ed inside he ans e s anda d, whe e he s ain gauges
a e loca ed, and no only ce ain empe a u e poin s bu also he empe a u e g adien s o e he
ansduce s and he adjacen componen s a e o be eco ded. All ansduce measu emen signals
should be co ec ed o changes in he en i onmen al condi ions.
2.3.1 Ampli ie and il e se ings
All signals should be eco ded using an adequa e sampling equency aking he o a ional speed nNTB
and he en isioned esolu ion o o bo h o que signals and he o a ional speed in o accoun . The
esolu ion aimed a is o = 1° o he maximum o a ional speed nmax .
The lowes limi o he sample equency sample can be calcula ed acco dingly:
sample ≥ nmax / o ⋅ 360°
,
(1)
whe e he sampling equency sample is in Hz and he o a ional speed nmax is in s-1. Fu he mo e, a low
pass il e should be implemen ed o a oid aliasing e ec s.
2.3.2 Timewise synch onisa ion o di e en da a se s
To synch onise all componen s o one da a acquisi ion sys em o wo di e en da a acquisi ion sys ems
including all hei componen s, ei he a collec i e ime se e , whe e all associa ed componen s use he
same ne wo k ime p o ocol o a simple synch onisa ion signal, which is eco ded and imes amped by
he di e en componen s and da a acquisi ion sys ems, can be deployed. Conce ning he accu acy,
bo h me hods a e su icien .
8 DOI: h ps://doi.o g/10.7795/530.20190111
When assigning he squa e-wa e me hod o synch onise he da a se s, he squa e-wa e signal is used
o shi he da a in pos -p ocessing and o e ase he empo al shi be ween he wo da a se s. The
squa e-wa e can ha e, e.g., an ampli ude o u
sync=±5 V and a equency o squa e = 0.2 Hz. While a
ough alignmen o he da a se s is achie ed by he logged s a ime and by dis inc i e signal changes
as shown in Figu e 2a), he ine synch onisa ion is based on he squa e-wa e signal, which is depic ed
in Figu e 2b).
An ad an age o he imewise synch onisa ion using a squa e-wa e signal is i s easy implemen a ion in
di e en es benches wi h all kinds o da a acquisi ion sys ems.
Figu e 2 Timewise synch onisa ion o he da a se s o he o que ans e s anda d and he nacelle es bench
using an ideal squa e-wa e signal, which is eco ded by bo h da a acquisi ion sys ems, o a p ecise
alignmen o he di e en da a se s.
2.4 Example o a se -up
In he example o a calib a ion se -up in Figu e 3, he o que ans e s anda d ha measu es he
e e ence o que is placed di ec ly a he hub lange o he de ice unde es as equi ed.
Mo eo e , an o e iew o he equi emen s on he ans e s anda d based on a su ey o es bench
ope a o s wi hin he EMPIR 14IND14 p ojec is lis ed in Table 3, while he gene al equi emen s
ega ding he dimensions and he weigh o he ans e s anda d a e lis ed in Table 4.
Figu e 3 The e e ence o que ansduce o calib a e he o que measu emen in a nacelle es bench is ins alled
di ec ly a he hub lange o he de ice unde es , whe e he mechanical inpu o he de ice unde es is
o be de e mined (4 MW nacelle es bench o he Cen e o Wind Powe D i es a RWTH Aachen).
To que
ansduce Re e ence o que
ansduce
Mo o
Load applica ion
sys em
Nacelle
14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide
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Table 3 Requi emen s o he RWTH Aachen es bench on o que ans e s anda ds o calib a ing nacelle es
benches ega ding he ca ying capaci y aken om [8].
To que
Nominal o que
kN m
± 6000
Maximal o que
kN m
± 7000
To que measu emen
accu acy
%
0.1
Fo ces and momen s
Pa asi ic loads
Ope a ing loads
Fo ces (Fx, Fy, Fz)
kN
± 100, ± 100, ± 100
± 1450, ± 2000, ± 2000
Maximum o ces (Fx, Fy, Fz)
kN
± 100, ± 100, ± 100
± 2000, ± 3000, ± 3000
Momen s (My, Mz)
kN m
± 100, ± 100
± 7500, ± 7500
Maximum momen s (My, Mz)
kN m
± 100, ± 100
± 15000, ± 15000
Fo ces/momen s mus be ansmi ed
Requi emen
Measu emen o o ces/momen s
Op ional
Li ecycles
S a ic s ess assessmen
(cycles @ max. o que)
5000
Fa igue s ess assessmen
(cycles @ max. o que)
Failsa e
1012
Kinema ic
Nominal o a ional speed
min-1
12
Maximum o a ional speed
min-1
25
Measu emen du ing o a ion
Requi emen
Measu emen in bo h o a ional di ec ions
Requi emen
Table 4 Dimensional equi emen s o PTB’s 1.1 MN m o que s anda d machine on a o que ansduce o be
calib a ed and, a e wa ds, o be deployed o calib a e he o que measu emen ins umen in he nacelle
es benches o RWTH Aachen.
Dimensions
Maximum lange diame e o calib a ion machine
m
1.25
Maximum lange diame e o es bench
m
4.5
Minimum leng h o calib a ion machine
m
0.6
Maximum leng h o calib a ion machine
m
2.2
Maximum weigh o calib a ion machine
2
Flanges: h ough-hole
Requi emen
• 30 x M36 on bol ci cle Ø 900 mm
Requi emen
• Fo es benches, an adap e is equi ed
Op ional
Addi ionally, he e is a lis o me ological equi emen s on he beha iou o he ans e s anda d in
Table 5.
Table 5 Me ological equi emen s on a o que ans e s anda d o become an adequa e o que ans e s anda d.
Me ological pa ame e s
Non-linea i ies
≤ ± 0.05 %
Hys e esis
≤ 2.9·10-5 mV/V
In e pola ion de ia ion
≤ |0.019| %
D i o e ime
≤ 8·10-3 %
C eep (sho e m c eep)
≤ |3·10-3| %
An example o a o que ans e s anda d o nacelle es bench calib a ion is shown in Figu e 4. This
ans e s anda d is owned by PTB, he na ional me ology ins i u e o Ge many, and was p oduced by
Ho inge Baldwin Mess echnik GmbH. I has a measu emen ange o 5 MN m and is s a ically
calib a ed up o 1.1 MN m wi h an expanded ela i e unce ain y o 8.8·10-4 (k = 2) acco ding o
DIN 51309 (which is compa able o EURAMET cg-14) using he wo ld’s la ges o que s anda d machine
loca ed a PTB. Due o he e y small non-linea i ies o he o que ans e s anda d, a linea eg ession
cu e was asce ained o clockwise o que load applied in inc easing and dec easing s eps:
M = 3851.1 kN m/(mV/V) ⋅ S
.
(2)
Abo e 1.1 MN m, a calib a ion is no possible. To p edic he ela ion be ween he ou pu signal and he
applied o que, including a p edic ed measu emen unce ain y aking he p edic ion i sel in o accoun ,
an ex apola ion me hod was de eloped.
16 DOI: h ps://doi.o g/10.7795/530.20190111
So-called cha ac e isa ion maps p o ide a simple solu ion o ec i ying his p oblem. A simila p ocedu e
o his has been sugges ed o o a o y powe measu emen [1].
Mos es benches ha e a de ined main di ec ion o o a ion. Fo hese es benches, only one di ec ion
o o que load is o be calib a ed. Howe e , i downwind nacelles a e es ed on he es bench, bo h
o que applica ion di ec ions a e o be calib a ed. Mo eo e , since nega i e o que can appea du ing
b aking scena ios, he e ec o applying nega i e o que on he hys e esis beha iou and he ze o e u n
should be analysed o all nacelle es benches.
To de ine he measu emen poin s o he cha ac e isa ion maps, he ypical ope a ing ange o he es
bench, depending on he commonly es ed de ices, is o be lis ed. The ypical ope a ing ange is
depic ed in Figu e 9 in he o m o a blue ec angle. I should be poin ed ou ha he ange o he
cha ac e isa ion map is limi ed by he ins alled de ice unde es du ing he calib a ion measu emen s.
Fo ha eason, he de ice unde es is o be picked acco dingly.
Figu e 9 Schema ic depic ion o a cha ac e isa ion map based on he ypical es ing ange o a nacelle es bench
wi h a uni o m dis ibu ion o he measu emen poin s.
When he e a e no pa icula poin s wi hin he ope a ing ange which need o be calib a ed explici ly,
such as ypical maximum o que loads o ce ain de ices unde es , he load s eps should be sp ead
e enly as shown in Figu e 9 in he o m o he Xs. In gene al, he calib a ion should co e he en i e
ope a ing ange o he es bench by epea ing he s anda d calib a ion wi h di e en combina ions o
o que load and o a ional speed (Figu e 10). To in es iga e he in luence o o a ional speed on he
o que measu emen , he e a e wo di e en ca ego ies o cha ac e isa ion maps: o CM1 (CM1a and
CM1b in Figu e 10), he o que is pe iodically ixed while he o a ional speed is al e ed s epwise; and
o CM2 (CM2a and CM2b in Figu e 10), he o a ional speed is kep cons an pe iodically while he
o que load is inc eased and dec eased. All o ms o he cha ac e isa ion map ha e he same ope a ing
ange. To de e mine he hys e esis o he es bench o que ansduce , each calib a ion poin should
be me wice du ing one load cycle: i s when aising he inc emen and second when a enua ing i
again. A en ion is o be paid o omi ing o a ional speed s eps close o eigen equencies o he sys em,
which would lead o undesi ed dynamic e ec s.
He e again, bo h he o que and o a ional speed can be inc eased o accele a ed espec i ely s epwise
as a amp, a s ep o a sine, whe eby he amp is he mos common one. Mo eo e , i his ype o
combined calib a ion is no su icien , single calib a ions o each ypical load, so-called pa ial ange
calib a ions, can be pe o med. Fo a s a is ical e alua ion o he calib a ion measu emen s, each
cha ac e isa ion map is o be epea ed wice o each load s ep is o be passed a leas ou imes. Should
a calib a ion like his no be possible a all due o a lack o access o he con ol sys em o he de ice
unde es , he calib a ion has o be pe o med in he median o he ypical es ing ange (see Figu e 9c))
wi h a sui able s anda d de ice unde es . Because o he se -up and he pe manen ly ac ing con ol
sys ems in a es bench, he de e mina ion o he ansduce c eep is no possible, which should no
pose a p oblem.
A leas one map pe ca ego y (CM1 and CM2) is o be pe o med in o de o in es iga e he in luence
o he o a ional speed on he o que measu emen . I a closed loop con ol is no possible, hen
pe o ming only CM2 is su icien , since he ep oducibili y o CM1 would no be good wi hou a closed
loop con ol anyway.
To que
Ro a ional
speed
ypical es ing ange
measu emen poin
To que
Ro a ional
speed
To que
Ro a ional
speed

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DOI: h ps://doi.o g/10.7795/530.20190111 17
Figu e 10 Example o di e en load s ep sequences o a calib a ion wi h o que being inc eased (and dec eased)
and o a ional speed being accele a ed and decele a ed a each o que s ep and ice e sa.
3.7 C oss alk e ec s
The assembly p ocess and he in eg a ion o he nacelle in o he es bench a e challenging, because
o he la ge masses and dimensions o nacelles. Fo example, a 5 MW nacelle has he ollowing
dimensions: 6.5 m heigh , 6.5 m wid h and 17 m leng h and a o al mass o 290 . E en a e y accu a e
assembly leads o an axis misalignmen be ween he main sha o he es bench and he hub o he
nacelle. This axis misalignmen may be in he ange o up o 0.5 mm and, he eby, i may gene a e
pa asi ic loads in he o m o o ces (Fx, Fy, and Fz) and bending momen s (My and Mz) unde o a ion.
The con ol sys em o he load applica ion sys em ies o keep hese pa asi ic loads o ze o. Howe e ,
due o he inaccu acy o he con ol sys em, he pe ec limi a ion o he pa asi ic loads o ze o is no
possible in mos cases. Consequen ly, an applica ion o pu e o que du ing he calib a ion is no
possible. Figu e 11 shows examples o he addi ional loads on he o que ans e s anda d wi hin he
a e aging sequence o e an in ege numbe o dis inc o a ions (he e six o a ions).
Addi ional in luences on he o que ansduce a e no desi ed as hey no only ha e an in luence on he
in ended measu ing b idges bu also on he o he measu ing b idges, which causes an unin en ional
signal al e a ion.
Figu e 11 Pa asi ic loads du ing he calib a ion a he o que s ep o 1000 kN m and o a ional speed o 6.5 min-1.
18 DOI: h ps://doi.o g/10.7795/530.20190111
The close su eillance o addi ional loads is, he e o e, necessa y o a oid unwan ed in luences on he
o que measu emen . Howe e , mos pe iodic in luences o addi ional loads can be neglec ed due o
he a e aging o he o que signal.
To pu posely s udy c oss alk in luences on he o que signal, cha ac e isa ion maps simila o Figu e 12
a e sugges ed.
Figu e 12 Schema ic p inciple o in es iga ing he c oss alk in luence on he o que signal caused by addi ional
loads.
3.8 Calib a ion in e al
Fo es benches in ol ed in de elopmen es s o es benches in gene al o in he de elopmen o he
de ices unde es , he calib a ion in e al should no exceed 12 mon hs.
The calib a ion in e al o he o que measu emen ins umen in he es bench highly depends on he
se -up and he usage o he es bench and he quali y p ocedu e in he es bench. Fo es benches,
which a e mainly used o de e mine he e iciency o he de ice unde es , he ecommenda ion o he
calib a ion in e al is a he long a up o 24 mon hs.
A e e e y change o he unde lying eg ession cu e o any main enance o alignmen conce ning he
o que measu emen ins umen , a ecalib a ion is equi ed.
Ideally, a calib a ion a he beginning and a he end o a de ice unde es being assembled and es ed
would be p e e able. In eali y, howe e , he u ilisa ion and ac i i y o he es bench need o be
conside ed as well.
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4 E alua ion o he calib a ion esul including a measu emen
unce ain y
The se -up o calib a ing a o que ansduce in a es bench by using a o que ans e s anda d is
compa able o a e e ence o que calib a ion machine. In a e e ence o que calib a ion machine, a
calib a ed and e y well-known o que ansduce is deployed o calib a e ano he o que ansduce .
Due o he simila i y o he se -up, he e ec s du ing he calib a ion a e analogous.
O he han he load cycles, which a e based on EURAMET cg-14, he e alua ion o he calib a ion esul
is based on ISO 7500-1 [4]. ISO 7500-1 desc ibes he calib a ion o a o ce measu emen sys em in
ma e ial es ing machines. He e, he deployed me hod does no necessa ily demand ha he exac load
s eps a e me . Ins ead, an indica ion de ia ion be ween he ansduce o be calib a ed and he ans e
s anda d is calcula ed.
Fo he o que calib a ion in es benches, he calib a ion esul is adap ed o he calib a ion esul in
ISO 75100-1 and consis s o :
• he ela i e indica ion de ia ion q,
• he measu emen unce ain y uc o he indica ion de ia ion, and
• he e e sibili y (in case inc easing and dec easing o que load was applied).
The calib a ion esul is no a classi ica ion o he ansduce calib a ed as is common o calib a ions.
The calib a ion esul can be used in he o m o :
• a look-up able ( o co ec he esul by consul ing he able),
• a eg ession cu e ( o co ec he esul in pos -p ocessing), o
• a co ec ion o he unde lying eg ession cu e o he es bench ansduce ( equi es a second
calib a ion o he es bench ansduce using he co ec ed eg ession cu e o de e mine he
measu emen unce ain y).
The e alua ion o an example o a o que calib a ion unde cons an o a ion can be ound in he ollowing
publica ions:
P. Weidinge , G. Foye , S. Kock, J. Gnaue , R. Kumme 2018 P ocedu e o o que calib a ion unde
cons an o a ion in es iga ed on a nacelle es bench in P oc. o Senso en & Messsys eme 2018,
Nu embe g, Ge many
P. Weidinge , G. Foye , S. Kock, J. Gnaue , R. Kumme Calib a ion o o que measu emen unde
cons an o a ion in a wind u bine es bench submi ed o JSSS.
4.1 E alua ion o he ansduce o be calib a ed
The pe o mance o he o que ansduce o be calib a ed can be e alua ed by he ela i e indica ion
de ia ion q, he ela i e epea abili y b, he ela i e esolu ion a, and he de e mina ion o he ela i e
e e sibili y when a calib a ion o dec easing o que is desi ed. All he ollowing subsec ions a e
adap ed om ISO 7500-1.
4.1.1 Rela i e indica ion de ia ion
The ela i e indica ion de ia ion qj(ML) is he de ia ion o he o que measu emen ins umen in he es
bench om he o que ans e s anda d ela i e o he eal o que alue measu ed by he o que ans e
s anda d pe load s ep ML. I is o be calcula ed o each o he a leas wo epea ed load cycles j (1 and
2) o cha ac e isa ion maps:
qj(ML) = Mi,j(ML) - Mj(ML)
Mj(ML) ⋅ 100%
,
(14)
wi h
j = 1,…, n
,
whe e Mi is he inc easing o que load indica ed by he o que measu ing ins umen in he es bench,
and M is he inc easing o que load indica ed by he o que ans e s anda d.
The calib a ion esul is ep esen ed as a ela i e indica ion de ia ion q
(ML), which is he a i hme ic mean
o he ela i e indica ion de ia ion pe epe i ion qj(ML):
q
(ML) = 1
n∑qj(ML)
n
j = 1
.
(15)
Figu e 13 is an example o a depic ion o he ela i e indica ion de ia ion o a quasi-s a ic load cycle
unde cons an o a ion. To assess he calib a ion esul and he in e ela ion be ween he applied o que
20 DOI: h ps://doi.o g/10.7795/530.20190111
and he o a ional speed, no only is he ela i e indica ion de ia ion o be calcula ed, bu also he
s anda d de ia ion o his alue. Depending on he s anda d de ia ion o he epea ed measu emen s,
a dis inc ion be ween he o que de ia ions con ingen on he di e en applied o a ional speeds can be
made.
Figu e 13 Example o indica ion de ia ion o ou epe i ions and a e aged indica ion de ia ion.
4.1.2 Rela i e epea abili y
The quali y o epea ing he o que measu emen s in he es bench is desc ibed by he ela i e
epea abili y b. This ela i e epea abili y is calcula ed o each load s ep sepa a ely and is he di e ence
be ween he maximum indica ion de ia ion qmax and he minimum indica ion de ia ion qmin pe load s ep:
b(ML) = max
j(qj(ML)) - min
j(qj(ML))
.
(16)
The ela i e epea abili y is an impo an con ibu ion o he measu emen unce ain y and an example
o his is illus a ed in Figu e 13.
4.1.3 Rela i e esolu ion
Mos es benches a e s a e o he a and display he applied load digi ally. The e o e, he ocus
ega ding he esolu ion lies on digi al o que displays. In gene al, he esolu ion depends on he
esolu ion o he ampli ie ’s A/D con e e and he da a sa ing o ma . Howe e , i he indica ion
luc ua ion exceeds his esolu ion, he esolu ion is o be summed up by hal he span o he indica ion
luc ua ion. The indica ion luc ua ion is o be de e mined wi h he p ime mo e and he de ice unde
es swi ched on, bu wi h no load applied. To de e mine he indica ion luc ua ion, he signal is o be
a e aged pe e olu ion o e he a e aging sequence as depic ed in Figu e 14, hen he minimum and
maximum o he a e aged signals pe e olu ion a e o be ound and he di e ence is calcula ed.
Subsequen ly, he ela i e esolu ion a is o be de e mined o each load s ep depending on he applied
load:
a(ML) = (ML)
M(ML) ⋅ 100%
,
(17)
wi h
(ML) = max
l l(ML) - min
l l(ML)
2
,
(18)
whe e M is he o que load o he obse ed load s ep (a e aged alues o all epe i ions). The esolu ion
is o be ep esen ed in he same uni as he measu ed o que.
epea abili y
e e sibili y
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DOI: h ps://doi.o g/10.7795/530.20190111 21
Figu e 14 Schema ic igu e on how o de e mine he indica ion de ia ion pe load s ep.
4.1.4 Rela i e e e sibili y
Fo he special case ha a eg ession cu e o dec easing o que load is demanded, he ela i e
e e sibili y o he dec easing load can be de e mined. Howe e , i is o be emphasised ha he
e e sibili y highly depends on he maximum o que load applied be o ehand. To de e mine he ela i e
e e sibili y, he deployed o que ans e s anda d mus be calib a ed o dec easing o que load.
Mo eo e , o he e e sibili y measu emen s, only one dec easing load cycle is o be pe o med.
Based on he de ia ion be ween he o que measu emen alues o inc easing and dec easing load
s eps (Figu e 13), he ela i e e e sibili y is calcula ed:
= M - M'
M

⋅ 100%
.
(19)
4.2 Measu emen unce ain y
As men ioned abo e, he p e ailing calib a ion se -up is compa able o a e e ence calib a ion machine,
whe e he ansduce o be calib a ed is compa ed o a na ional s anda d. Thus, in gene al, o an NTB
calib a ion, he in luences on he ansduce o be calib a ed a e he same as hose in a e e ence o que
s anda d machine bu e en la ge .
The measu emen unce ain y i sel is based on he a o emen ioned ac o s and consis s o he ollowing
unce ain y con ibu ions:
• he esolu ion,
• he epea abili y, and
• he o que ans e s anda d.
All his esul s in he bes expec ed alue o he indica ion de ia ion and he co esponding expanded
measu emen unce ain y. The ollowing e alua ions a e based on ISO 7500-1 and a e adap ed o a
o que calib a ion unde o a ion.
4.2.1 Measu emen condi ions
In gene al, he in luences on he o que ansduce o be calib a ed a e he same as hose in a e e ence
o que s anda d machine bu e en la ge . The Ishikawa diag am in Figu e 15 lis s examples o possibly
occu ing in luences a ec ing he calib a ed o que measu emen in a nacelle es bench.
Mos in luences can be quan i ied and ca ego ised by he a o emen ioned p epa a o y ope a ions and
es s. Addi ionally, all se -up-speci ic e ec s, i.e., misalignmen s and ic ion in di e en componen s a e
di ec ly pa o he calib a ion esul and ha e al eady been conside ed in he measu emen unce ain y
by de e mining he epea abili y.
Eme gency b aking, which may occu and is o be es ed unde no mal es ing condi ions, should be
a oided du ing he calib a ion p ocess. A e eme gency b aking, he es bench is o be ope a ed wi h
maximum o que load in he d i ing di ec ion o a leas 3 min and a new ze o signal is o be de e mined.
In doing so, he hys e esis e ec due o he opposi e o que load is minimised.
1 2 3 4 5 6

22 DOI: h ps://doi.o g/10.7795/530.20190111
In he case ha di e en ampli ie s we e used o he calib a ion o he o que ans e s anda d han o
he calib a ion in he nacelle es bench, he di e ence be ween he di e se ampli ie s is o be accoun ed
o in he measu emen unce ain y o e en he indica ed o que alue.
Because o he signal a e aging o e a ce ain numbe o e olu ions, he dead-weigh in luence on he
o que signal can be neglec ed.
Figu e 15 Ishikawa diag am lis ing he in luences du ing he calib a ion o he o que measu emen in nacelle es
benches.
4.2.2 Unce ain y con ibu ion o he esolu ion
The unce ain y con ibu ion o he ela i e esolu ion o he o que measu emen ins umen in he es
bench u es o each examined load s ep is he squa e oo o he sum o he ollowing componen s
squa ed:
• he unce ain y componen due o he ela i e esolu ion o he o que measu emen ins umen
in he es bench unde load, which is deno ed as aM di ided by 2√3 because o he assump ion
o a ec angula dis ibu ion,
• he unce ain y componen due o he ela i e esolu ion o he o que measu emen ins umen
in he es bench a e load elease, which is deno ed as aZ di ided by 2√3 (same assump ion
o a ec angula dis ibu ion). The ela i e esolu ion o he o que measu emen a e load
elease is pa o he indica ion de ia ion o e e y load s ep because o he a o emen ioned
a ing o he o que alues o e e y load s ep.
The unce ain y con ibu ion o he ela i e esolu ion can be calcula ed o e e y load s ep as ollows:
u es(ML) = √(aM(ML)
2√3)2
+ (aZ
2√3)2
.
(20)
As he ela i e esolu ion a is exp essed in he uni %, he absolu e unce ain y con ibu ion o he ela i e
esolu ion u es is exp essed in % as well.
4.2.3 Unce ain y con ibu ion o he epea abili y
As men ioned be o e, he ela i e epea abili y is conside ed as an unce ain y con ibu ion o he o al
unce ain y o he indica ion de ia ion. The unce ain y con ibu ion o he epea abili y u ep is he
s anda d de ia ion o he bes expec ed alue qi in % and he ela i e mean indica ion de ia ion q
 in %,
whe e n is he numbe o epe i ions pe load s ep:
u ep(ML) = √1
n
(n
- 1) ∑ (q
j
(ML) - q
(ML))2
n
j
= 1
.
(21)
Sampling equency
Dead-weigh
Misalignmen
Humidi y
Tempe a u e/
Temp. g adien s
P essu e
D i
Measu emen unce ain y
En i onmen al
condi ions
C eep
To que ans e
s anda d
Calib a ed o que
in he wind u bine
es bench
S abili y
Resolu ion
EMC
Measu emen
condi ions
Misalignmen s
Pa asi ic loads LAS
To que in e sion
F ic ion in di . comp.
Ampli ie s To que ansduce
Ze o-poin de ia ion
Repea abili y
Re e sibili y
C eep
Fil e
Negligible
Gene al
e ec s
Se -up speci ic
e ec s
Ro a ional speed
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4.2.4 Unce ain y con ibu ion o he ans e s anda d
The unce ain y con ibu ion o he o que ans e s anda d us d is gi en by he ela i e calib a ion
unce ain y o he ans e s anda d ucal, which is s a ed in i s calib a ion ce i ica e, and addi ional
possible unce ain y con ibu ions (A, B, and C) due o de ia ing empe a u e and humidi y du ing he
calib a ion measu emen s, d i o e ime, and de ia ions because o he deployed combined linea
eg ession cu e o inc easing and dec easing o que load. The unce ain y con ibu ion o he o que
ans e s anda d is calcula ed acco ding o he ollowing:
us d(ML) = √(ucal(ML))2 + A2 + B2 + C2
.
(22)
As he unce ain y con ibu ion o he o que ans e s anda d is shown as a ela i e unce ain y, i is
exp essed as a pe cen age (%).
4.2.5 Expec ed alue o he indica ion de ia ion
The esul o he o que calib a ion is he bes expec ed alue o he mean ela i e indica ion de ia ion
q
(ML) o he o que measu emen ins umen in he es bench. Mo eo e , an expanded measu emen
unce ain y U(ML) belongs o his ela i e indica ion de ia ion, which is he p oduc o he co e age ac o
k and he combined unce ain y uc(ML):
UU(ML) = k ⋅ uc(ML) = k ⋅√∑(uj(ML))2
n
j=1
= k ⋅√(u es(ML))2 +(u ep(ML))2+(us d(ML))2
.
(23)
Addi ional unce ain y con ibu ions may be in luences o he deployed ampli ie s o he o que ans e
s anda d o signi ican in luences o he ic ion o que.
I is ecommended o use a co e age ac o o k = 2. In ce ain cases, k can also be calcula ed based
on he numbe o e ec i e deg ees o eedom as s a ed in he GUM.
Anno a ion: he measu emen unce ain y is an absolu e measu emen unce ain y o he ela i e
indica ion de ia ion, which is ep esen ed in he uni %. The absolu e measu emen unce ain y has he
same uni as i s e e ence alue. Consequen ly, he uni o he absolu e measu emen unce ain y is %.
4.2.6 Example o an unce ain y calcula ion
An example o a calcula ion o he measu emen unce ain y o o que calib a ion unde cons an
o a ion is gi en in P. Weidinge , G. Foye , S. Kock, J. Gnaue , R. Kumme Calib a ion o o que
measu emen unde cons an o a ion in a wind u bine es bench submi ed o JSSS.
This pape co e s a comple e conside a ion o a o que calib a ion unde cons an o a ion in a nacelle
es bench including he measu emen unce ain y budge and he empe a u e di e ence be ween he
calib a ion labo a o y, whe e he o que ans e s anda d was calib a ed, and he condi ions du ing he
nacelle es bench calib a ion. Mo eo e , a de ailed calcula ion o he ela i e indica ion de ia ion o
ou measu emen epe i ions is gi en. The expanded (k = 2) absolu e measu emen unce ain y U(ML)
o he bes expec ed alue o he ela i e indica ion de ia ion is calcula ed including he unce ain y
con ibu ion o he o que ans e s anda d, which comp ises he d i o he ansduce , he empe a u e
in luence and he unce ain y o he ampli ie calib a ion (special case).
24 DOI: h ps://doi.o g/10.7795/530.20190111
5 Calib a ion ou pu and bene i o he es bench ope a o
The esul o a o que calib a ion in nacelle es benches can be exp essed in di e en o ms:
• a look-up able (pos -p ocessing),
• a eg ession cu e (pos -p ocessing), o
• a co ec ion o he o que ansduce s unde lying he ans e cu e (addi ional calib a ion
equi ed a e wa ds).
In gene al, he possibly occu ing indica ion de ia ions in he o que measu emen o a nacelle es
bench can be co ec ed by all he di e en o ms o he calib a ion esul . Mo eo e , he calib a ion gi es
a measu emen unce ain y o he calib a ed ange, which is again a con ibu ion o he measu emen
unce ain y o he e iciency de e mina ion.
Tes bench ope a o s can bene i om knowing he de ia ion be ween hei in e nal o que measu ing
ins umen and a aced na ional o que s anda d and co ec ing his de ia ion o ob ain a mo e accu a e
o que measu emen esul . Fu he mo e, a e a calib a ion, he p ecision including he epea abili y o
he o que measu emen ins umen in he nacelle es bench is de e mined. Based on his, no only can
he e iciency o de ices unde es be de e mined mo e eliably, bu also he da a o alida e simula ions
and he epea able componen es ing gain c edibili y.
Wi h he s anda dised calib a ion o o que measu emen s in nacelle es benches, e iciencies o
de ices es ed on di e en es benches can be compa ed o each o he eliably.
14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide
DOI: h ps://doi.o g/10.7795/530.20190111 25
Glossa y
• Calib a ion: ope a ion ha , unde speci ied condi ions, in a i s s ep, es ablishes a ela ion
be ween he quan i y alues wi h measu emen unce ain ies p o ided by measu emen
s anda ds and co esponding indica ions wi h associa ed measu emen unce ain ies and, in a
second s ep, uses his in o ma ion o es ablish a ela ion o ob aining a measu emen esul
om an indica ion (VIM 2.39).
• Cha ac e isa ion map: load cycle co e ing he ypical ope a ion ange o a nacelle es bench.
The cha ac e isa ion map is limi ed by he de ice unde es ins alled du ing he calib a ion.
• C oss alk e ec : in luence o addi ional mul i-axial loads no only on he espec i ely in ended
measu ing b idges bu also on he o he measu ing b idges, which causes an unin en ional
signal al e a ion.
• Load cycle: ange o applied load on a measu ing ins umen du ing calib a ion.
• Measu emen unce ain y: non-nega i e pa ame e cha ac e ising he dispe sion o he quali y
alues being a ibu ed o a measu and, based on he in o ma ion used (VIM 2.26).
• To que ans e s anda d: calib a ed and e y well-known o que ansduce , which is used o
ace o que measu emen o he na ional s anda d.
• Ze o signal: o se alue o a ansduce in non-loaded condi ion. The ze o signal is used o a e
all measu emen signals o he ollowing load cycle.