Dlvn 250 Nkeptchuan Qtkd

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LVN VN BN K THUT O LNG VIT NAM

LVN 250 : 2012

NHIT K IN TR PLATIN CHUN QUY TRNH KIM NH

Standard Platinum Resistance Thermometers Verification procedures

H NI - 2012

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Li ni u: LVN 250 : 2012 do Ban k thut o lng TC 11 Phng tin o nhit v cc i lng lin quan bin son. Vin o lng Vit Nam ngh, Tng cc Tiu chun o lng Cht lng ban hnh.

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VN BN K THUT O LNG VIT NAM LVN 250 : 2012

Nhit k in tr platin chun Quy trnh kim nh Standard platinum resistance thermometers Verification procedures

1 Phm vi p dng Vn bn k thut ny quy nh quy trnh kim nh ban u, kim nh nh k v kim nh sau sa cha theo phng php so snh cc loi nhit k in tr platin chun c in tr danh nh 25 hoc 100 , c phm vi o nhit t -40 oC n 420 oC v chnh xc (hoc khng m bo o) khng vt qu 0,05 oC (50 mK). 2 Thut ng v nh ngha Cc t ng trong vn bn ny c hiu nh sau: 2.1 Nhit k in tr platin chun c kim nh (sau y gi tt l nhit k b kim): l dng c o nhit c chnh xc cao, v bo v thng l thy tinh hoc kim loi chu nhit, u o l dy platin c tinh khit cao, c in tr danh nh 25 hoc 100 . 2.2 u o ca nhit k in tr: l dy platin c tinh khit, c tnh cht thay i in tr khi nhit thay i, c cun trn khung lm t vt liu cch in, cch nhit. 2.3 Dy dn trong: gm 4 dy platin nm trong v bo v, c tinh khit nh u o ca nhit k, ni t u o n u ni ngoi ca nhit k in tr. 2.4 Dy dn ngoi: gm 4 dy ni t u ni ngoi ca nhit k in tr n u ni vo ca thit b o in tr hoc nhit . 2.5 Cc u ni ca nhit k in tr: gm 4 u dy u ni vi thit b o, chia thnh 2 u dng v 2 u p, thng k hiu C1P1C2P2; AABB; CcTt hoc phn theo mu, ph hp vi quy nh quc t. 2.6 in tr danh nh: l gi tr in tr danh nh ca nhit k in tr 0 C. 2.7 Dng in danh nh: l gi tr dng in danh nh chy qua nhit k in tr khi o nhit ; dng danh nh l 1 mA i vi loi nhit k in tr 25 v 100 ( 0 C).

LVN 250 : 2012

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2.8 in tr chun ngoi: l cc cun in tr chnh xc cao t trong bnh iu nhit hoc ngoi khng kh, thng c gi tr danh nh 25 ,100 , hoc 300 s dng vi dng xoay chiu hoc mt chiu. 2.9 Thit b o in tr: l cu o in tr hoc cu o t s in tr. 3 Cc php kim nh Phi ln lt tin hnh cc php kim nh ghi trong Bng 1.

Bng 1

TT Tn php kim nh Theo iu, mc ca

quy trnh

Ch kim nh Ban u nh k Sau sa

cha 1 Kim tra bn ngoi 7.1 + + + 2 Kim tra k thut 7.2 + + + 3 Kim tra o lng 7.3 + + +

4 Phng tin kim nh Phi s dng phng tin kim nh ghi trong Bng 2.

Bng 2

TT Tn phng tin kim nh c trng k thut o lng

c bn p dng cho iu, mc ca

quy trnh 1 Chun o lng

1.1 Nhit k in tr platin chun - Phm vi o t -40 oC n 420 oC - khng m bo o khng ln hn 1/5 khng m bo o ca thit b kim nh.

7.3

2 Phng tin s dng cng vi chun

2.1 Thit b o in tr - Phm vi o t 0 n 400 k - khng m bo o khng ln hn 1 ppm (i vi in tr ngoi) v khng ln hn 6 ppm (i vi in tr trong).

7.3

LVN 250 : 2012

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2.2 in tr chun ngoi - Gi tr in tr ph hp vi nhit k b kim - chnh xc khng ln hn 1 ppm

7.3

2.3 Cc bnh iu nhit cht lng

- Phm vi lm vic ph hp vi phm vi o ca nhit k b kim - khng m bo o khng ln hn 0,01 oC.

7.3

2.4 Bnh im 0 oC (hoc bnh im ba ca nc)

- chnh xc (hoc khng m bo o) khng ln hn 0,01 oC 7.3

3 Phng tin ph

3.1 L nhit k b kim - Phm vi lm vic phi ph hp vi phm vi o ca nhit k b kim

7.2

3.2 Kp g, giy lau, cn tinh khit

7.1; 7.2, 7.3

5 iu kin kim nh Khi tin hnh kim nh phi m bo cc iu kin sau y: 5.1 Phi c h thng quan trc mi trng: theo di nhit , m ti ni kim nh. 5.2 Phi m bo cc iu kin v nhit , m ph hp vi yu cu k thut ca cc thit b chun v nhit k b kim, hoc phi tho mn iu kin sau: - Nhit : 23 oC 2 oC; - m khng ln hn 60 %RH.

6 Chun b kim nh Trc khi tin hnh kim nh phi thc hin cc cng vic chun b sau y: 6.1 Lm sch nhit k b kim, chun b cc phng tin ph nh trong mc 3 Bng 2. 6.2 Chun b bnh im 0 C hoc bnh im ba ca nc.

LVN 250 : 2012

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7 Tin hnh kim nh 7.1 Kim tra bn ngoi Phi kim tra bn ngoi theo cc yu cu sau y: 7.1.1 Nhit k b kim phi c y k, m hiu, nc sn xut, v ti liu k thut km theo. 7.1.2 V bo v nhit k b kim khng b nt, v, bp. u o nhit k khng b chp, t, cc vng dy cun phi t do trn gi dy, dy ni trong khng b son, chp vo nhau (i vi nhit k b kim c v thu tinh). 7.2 Kim tra k thut Phi kim tra k thut theo cc yu cu sau y: 7.2.1 Trc khi tin hnh kim nh, nhit k b kim c nh gi n nh ti im 0 oC hoc im ba ca nc trc v sau khi ti nhit cao nht trong phm vi o. Trnh t kim tra nh sau: 7.2.1.1 o gi tr in tr (R1) ca nhit k b kim ti im 0 C hoc im ba ca nc. 7.2.1.2 nhit k b kim trong l khong 4 gi vi nhit 450 C: Sau khi , rt nhit k b kim ra lm ngui t nhin nhit phng. 7.2.1.3 o li gi tr in tr (R2) ca nhit k b kim, nh trong mc 7.2.1.1. 7.2.2 Hiu gi tr nhit trc v sau khi phi tho mn: t = ci (R1 R2 ) +0,003 oC : i vi nhit k b kim v thu tinh, t = ci (R1 R2 ) +0,010 oC : i vi nhit k b kim v kim loi. Ghi ch: ci l nhy nhit-in ca nhit k b kim. 7.2.3 Nu khng tho mn cc gi tr trn, nhit k b kim phi li; trng hp vn khng t, dng kim nh. 7.3 Kim tra o lng Nhit k in tr platin chun c kim tra o lng theo trnh t, ni dung, phng php v yu cu sau y: 7.3.1 Quy nh chung: 7.3.1.1 Phng php kim nh c thc hin bng cch o gi tr in tr ca

LVN 250 : 2012

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nhit k b kim ti cc im nhit (im kim tra) c th hin bng h thng chun quy nh trong Bng 2. 7.3.1.2 Ni dung ca php kim nh l thit lp hm quan h in tr - nhit (phng trnh ni suy) ca nhit k b kim. 7.3.1.3 Cc im kim tra l cc im nhit cch u nhau trong di nhit kim nh (phm vi o ca nhit k b kim). S im kim tra ph thuc vo s cc h s ca hm quan h in tr - nhit v khng t hn 4 im cho mi h s. 7.3.1.4 S ln o ti mi im nhit kim tra khng t hn 5. 7.3.2 Tin hnh kim tra 7.3.2.1 Vn hnh cc phng tin s dng cng vi chun theo ng hng dn s dng. 7.3.2.2 Ni cc nhit k in tr (chun v b kim) vo thit b o in tr. 7.3.2.3 Nhng nhit k b kim vo bnh im 0 oC, o v ghi gi tr in tr R(0 oC) ca nhit k ti 0 oC khi s ch ca thit b o n nh. Vic o ti im 0 oC c tin hnh vi hai dng i1 = 1 mA v i2 = 2 mA. 7.3.2.4 Nhng nhit k chun v b kim vo bnh iu nhit, t nhit ca bnh iu nhit ng vi im kim tra u tin, sau khi nhit n nh o v ghi cc gi tr nhit ca nhit k chun v in tr ca nhit k b kim. 7.3.2.5 Tip tc tin hnh o nh mc 7.3.2.4 ti tt c cc im kim tra quy nh ti mc 7.3.1.3 theo chiu tng ca nhit . 7.3.2.6 Sau khi o xong ti im kim tra cui cng, tin hnh o nh mc 7.3.2.4 ti im kim tra ng vi khong gia di nhit kim nh hoc ti im 0 oC (i vi nhit k c phm vi o n 250 oC). 7.3.3 Tnh ton kt qu kim nh 7.3.3.1 Tnh cc gi tr trung bnh ca nhit k chun v nhit k b kim ti mc 7.3.2 7.3.3.2 Tnh cc h s a5, b5, a8, b8 theo cc phng trnh ni suy ca ITS-90 nh sau:

W(T90) = W(T90) Wr(T90) = a5[W(T90) -1] +b5[W(T90) -1]2

W(T90) = W(T90) Wr(T90) = a8[W(T90) -1] +b8[W(T90) -1]2

LVN 250 : 2012

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hoc cc h s A, B, C theo phng trnh ni suy Callendar Van Dusen: R(t) = R(0) [1 + At + Bt2] t 0 oC R(t) = R(0) [1 + At + Bt2 + C(t 100)t3] t < 0 oC

7.3.3.3 Tnh t nung nng ca nhit k b kim: l hiu gi tr in tr ca nhit k b kim o c ti 0 oC vi dng i1 = 1 mA v dng i2 = 2 mA

Rnn = R(i2) R(i1) 7.3.3.4 Tnh hi tr ca nhit k b kim: l hiu gi tr in tr ca nhit k b kim o c ti im kim tra ng vi khong gia di nhit kim nh hoc ti im 0 oC trong (Rtr) v sau khi kim nh (Rs).

Rht = Rtr Rs 7.3.4 nh ga khng m bo o khng m bo o ca kt qu kim nh c c lng vi h s ph k = 2 v tin cy 95%. khng m bo o pht sinh do nhiu yu t gy sai s v c quy v hai thnh phn chnh sau: - khng m bo o chun loi A (type A): uA - khng m bo o chun loi B (type B): uB 7.3.4.1 khng m bo o chun loi A: uA Gm 3 thnh phn, c tnh theo cng thc:

uA = (u1A2 + u2A2 + u3A2)1/2 Trong : - u1A v u2A l khng m bo o do tn mn ca kt qu o ca nhit k chun v nhit k b kim; cc khng m bo o ny tnh theo lch chun lu tch t cc im kim tra; - u3A l khng m bo o do sai lch lm khp (sai lch gia cc gi tr in tr o c vi cc gi tr in tr tnh ton theo phng trnh ni suy ca nhit k b kim) 7.3.4.2 khng m bo o chun loi B: uB Gm 8 thnh phn, c tnh theo cng thc sau:

uB = ( 2B72B62B52B42B32B22B1 uuuuuuu ++++++ )1/2

LVN 250 : 2012

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Trong : - u1B l khng m bo o ca nhit k chun, thnh phn ny c tnh t khng m bo m rng Uch ca nhit k chun cho trong giy chng nhn hiu chun:

u1B = Uch/2

- u2B l khng m bo o do tri hng nm ttr ca nhit k chun: u2B = ttr /2 3

- u3B l khng m bo o ca thit b o in tr, thnh phn ny tnh t khng m bo m rng / chnh xc Utb ca thit b o in tr cho trong giy chng nhn hiu chun (tnh c cho nhit k chun v nhit k b kim):

u3B = ci Utb /2

- u4B l khng m bo o ca in tr chun ngoi, gm thnh phn u4B-1 tnh theo khng m bo o cho trong giy chng nhn hiu chun v thnh phn u4B-2 tnh theo n nh ca bnh iu nhit tstab v h s nhit in tr ca in tr chun (thnh phn ny tnh c cho nhit k chun v nhit k b kim):

u4B = (u4B-12 + u4B-22)1/2

u4B = ci [(Ut/2)2 + ( tstab / 3 )2]1/2 - u5B l khng m bo o ca bnh iu nhit, gm thnh phn u5B-1 tnh theo n nh tod v thnh phn u5B-2 tnh theo ng u tdd ca bnh iu nhit:

u5B = (u5B-12 + u5B-22)1/2

u5B = [(tod / 3 )2 + (tdd / 3 )2]1/2 - u6B l khng m bo o do hi tr Rht ca nhit k b kim:

u6B = ci Rht /2 3 - u7B l khng m bo o do hiu ng t nung nng ca nhit k b kim:

u7B = ci Rnn /2 3 - u8B l khng m bo o ca bnh im 0 oC (hoc bnh im ba ca nc), thnh phn ny c tnh t khng m bo o m rng U0 ca im 0 oC (hoc bnh im ba ca nc):

u8B = U0/2

LVN 250 : 2012

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7.3.4.3 khng m bo o chun tng hp: uC = (uA2 + uB2)1/2

7.3.4.4 khng m bo o m rng: U = k.uC = 2.uC 7.3.4.5 Cc thnh phn khng m bo o c ghi trong Bng 3.

Bng 3 S TT

Ngun gc gy ra khng m bo o Ngun tnh ton Phn b

01

02

03

1 KB chun loi A 1. 1 tn mn kt qu o ca nhit k chun, u1A

1.2 tn mn kt qu o ca nhit k b kim, u2A

1.3 Sai lch lm khp, u3A

S liu o c

S liu o c.

S liu tnh ton

Chun

Chun

Chun

04

05

06

07

08

09

10

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2 KB chun loi B 2.1 Nhit k chun, u1B 2.2 tri ca nhit k chun, u2B 2.3 Thit b o in tr, u3B 2.4 in tr chun, u4B 2.5 Bnh iu nhit, u5B 2.6 hi tr ca nhit k b kim, u6B 2.7 Hiu ng t nung nng, u7B 2.8 Bnh im 0oC (hoc bnh im ba ca nc), u8B

Chng nhn Chng nhn Chng nhn Chng nhn Chng nhn S liu o c S liu o c Chng nhn

Chun Ch nht Chun Chun Chun Ch nht Ch nht Chun

7.3.4.6 khng m bo o ca nhit k b kim phi tho mn yu cu quy nh ti Bng 4 ph lc 2.

LVN 250 : 2012

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8 X l chung 8.1 Nhit k in tr platin chun sau khi kim nh nu t cc yu cu quy nh theo quy trnh kim nh ny c cp chng ch kim nh (tem kim nh, du kim nh, giy chng nhn kim nh ...) theo quy nh. 8.2 Nhit k in tr platin chun sau khi kim nh nu khng t mt trong cc yu cu quy nh ca quy trnh kim nh ny th khng cp chng ch kim nh mi v xa du kim nh c (nu c). 8.3 Chu k kim nh ca nhit k in tr platin chun l: 01 nm.

Ph lc 1

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Tn c quan kim nh BIN BN KIM NH ....................................... S ....................

Tn chun o lng : .................................. Kiu : .. S :........... C s sn xut :Nm sn xut :........... c trng k thut :................ Ni s dng : ........... Phng php thc hin : .............................................................................. Chun, thit b chnh c s dng : ............ iu kin mi trng : ........... Ngi thc hin : ............ Ngy thc hin : ..............

KT QU

1. Kim tra bn ngoi: t: Khng t: 2. Kim tra k thut: t: Khng t: 3. Kim tra o lng:

S LIU V KT QU

im kim tra (C )

S c trung bnh ca nhit k chun (oC )

S c trung bnh ca nhit k b kim ( ), i1 = 1 mA

S c trung bnh ca nhit k b kim ( ), i2 = 2 mA

hi tr:

t nung nng:

* khng m bo o m rng ca php kim nh l U95 =.....mK (95 %C.L.; k = 2).

t: Khng t: 4.Kt lun t: Khng t:

Ngi sot li Kim nh vin

Ph lc 2

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CHNH XC/ KHNG M BO O CHO PHP CA CC LOI NHIT K IN TR PLATIN CHUN

Bng 4

Phm vi o

(C) Loi nhit k nhy (/C)

n nh (C)

chnh xc/ khng m bo o

(C)

(-40 420)

25,5 0,5 v Thy tinh

25,5 0,5 v Kim loi

100 1 v Kim loi

0,1

0,1

0,4

0,001

0,003

0,01

0,01

0,02

0,05

Ph lc 3

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S KIM NH CHUN V CC PHNG TIN O NHIT ( tham kho)

ITS 90

CHUN QUC GIA Phm vi o (-40 420) C

Phng php im chun

Nhit k in tr platin chun Phm vi o: (-40 420) C

U95 = (2 10) mK

Ngun vt en chun Phm vi o: (30 42) C

U95 50 mK

Nhit k in tr platin chun Phm vi o: (-40 420) C

U95 = (10 50) mK

Nhit k thy tinh thy ngn chun Phm vi o: (-40 420) C

U95 = (0.01 0.5) 0C

Phng php So Snh

Phng php So Snh

Phng php So Snh

Nhit k bc x hng ngoi o nhit tai c th ngi

Phm vi o: (30 42) C U95 0.2 C

Phng php So Snh

Phng php So Snh

Nhit k thy tinh thy ngn; nhit k y hc; nhit k cc i, cc tiu

Phm vi o: (-40 420) C U95 5 C

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Dlvn 250 Nkeptchuan Qtkd