its-90 fixed points · – melting ice, 冰的熔化 ... -189.3442°c to 0.01°c 4 ar, hg, tpw...

Rong Ding ITS-90 Seminar Fluke Corp.

固定点和SPRT温度计的使用及检定


第一部分：

固定点


固定点

• 自然界的一些系统有相同的温度。比如：

– melting ice, 冰的熔化

– boiling water at sea level, 海平面上水的沸点

– interior of a healthy human body, 健康人的体内温度

– phase equilibrium points of pure materials. 纯金属的相平衡点

• These “landmarks” of temperature can serve as thermometric

fixed points. 这些特征温度点可以作为温度固定点


Temperature

Time

tm

Ideal Pure Metal Melting Curve

理想纯金属（100%纯度）的熔化过程

Melting plateau


Ideal Pure Metal Freezing Process

The freezing process is just the reverse of the melting process

Temperature

time

tf

理想纯金属的凝固过程

Freezing Plateau


金属的熔化曲线

实际金属和理想金属的熔化曲线比较


Freezing Curves of Metal

实际金属和理想金属的凝固曲线比较


水的相图

Solid

Vapor

Liquid

P0

Ice Point Steam Point T

P


Substance

and state ITS-27 ITS-48

IPTS-48

(AM 1960) IPTS-68

IPTS-68

(AM 1975) ITS-90

He VP 3 to 5

e-H2 TP 13.81 13.81 13.8033

e-H2 VP 17.042 17.042 ~ 17

e-H2 VP 20.28 20.28 ~ 20.3

Ne TP 24.5561

Ne BP 27.102 27.102

O2 TP 54.361 54.361 54.3584

Ar TP 83.798 83.8058

O2 BP 90.18 90.180 90.18 90.188 90.188

Hg TP 234.3156

ITS-90定义的固定点


Substance

and state ITS-27 ITS-48

IPTS-48

(AM 1960) IPTS-68

IPTS-68

(AM 1975) ITS-90

H2O FP 0.000 0

H2O TP 0.01 0.01 0.01 0.01

Ga MP 29.7646

H2O BP 100.000 100 100 100 100

In FP 156.5985

Sn FP 231.9681 231.9681 231.928

Zn FP 419.505 419.58 419.58 419.527

S BP 444.60 444.6 444.6

Al FP 660.323

Ag FP 960.5 960.8 960.8 961.93 961.93 961.78

Au FP 1063 1063.0 1063 1064.43 1064.43 1064.18

Cu FP 1084.6

Defining Fixed Points of the ITS’s (°C)


不同国际温标定义的固定点

BP FP MP TP Total

ITS-27 3 3 6

ITS-48 3 3 6

IPTS-48 (1960) 3 3 1 7

IPTS-68 5 4 3 12

IPTS-68 (1975) 5 4 4 13

ITS-90 3 7 1 6 17


从 0.65 K 到 5.0 K

i

i

iC

BpAAT

9

1

090

ln

氦气蒸汽压力-温度方程：

From 0.65 K to 3.2 K, 1.25 K to 2.1768 K, and from 2.1768 K to

5.0 K, different values of coefficients A0, Ai, B, and C are given in

ITS-90.


从 3.0 K 到 24.5561 K

4.2 K to 24.5561 K with 4He

VNB

cpbpaT

X /1

2

90

2

90 cpbpaT

3.0 K to 24.5561 K with 3He or 4He

恒体积气体温度方程

63

90

2

90

1

90903 10/82.13/04.91/98.33669.16 KTKTKTTB

65

90

4

90

3

90

2

90

1

90904 10/8.3252/2.4033/2.1799/53.383/05.374708.16 KTKTKTKTKTTB


从 13.8033 K 到 961.78 C

measured with thermometer.

a specified deviation function evaluated by thermometer calibration.

reference function defined by ITS-90

9090r90 TWTWTW

16.273

90

R

TRTW 90TW

90r TW

铂电阻温度计方程


从 13.8033 K 到 273.16 K

Inverse Function

Reference Function

12

1

90090r

5.1

5.116.273lnln

i

i

i

TAATW

i

i

ri

TWBB

T

15

1

61

900

90

35.0

65.0

16.273

Platinum Resistance Thermometer Equations


从 0 C 到 961.78 C

Inverse

Function

Reference Function

i

i

i

TCCTW

9

1

90090r

481

15.754

9

1

90r090

64.1

64.2

i

i

i

TWDDt

铂电阻温度计方程 Platinum Resistance Thermometer


SPRT 的偏差函数

5

1

90

2

909090 ln11i

ni

i TWcTWbTWaTW

90r9090 TWTWTW

13.8033 K to 273.16 K

At ITS-90 defining fixed points, Wr(T90) can be calculated or obtained directly from

the ITS-90 given table, and W(T90) is measured. Coefficients a, b, and ci can be

obtained from measurements at the defining fixed points.


9090909090 ln11 TWTWbTWaTWTW r

From 83.8058 K to 273.16 K

SPRT 偏差函数

From 0 C to 961.78 C

2323.660

32

90 111 WWdWcWbWaTW

Determined from the measured deviation W from Wr(T90) at the freezing point of silver.


普朗克辐射定律: 961.78 C以上

X = Ag or Au or Cu; c2=0.014388

1

1902

902

90

90

Tc

XTc

e

e

XTL

TL


使用ITS-90固定点检定SPRT

Temperature Range Subranges Fixed Points Used Coefficients

-189.3442°C to 0.01°C 4 Ar, Hg, TPW R(tpw), a4, b4

-38.8344－ 29.7646 5 Hg, TPW, Ga R(tpw), a5, b5

0°C to 961.78°C 6 TPW, Sn, Zn, Al, Ag R(tpw), a6, b6, c6, d

0°C to 660.323°C 7 TPW, Sn, Zn, Al R(tpw), a7, b7, c7

0°C to 419.527°C 8 TPW, Sn, Zn R(tpw), a8, b8

0°C to 231.928°C 9 TPW, In, Sn R(tpw), a9, b9

0°C to 156.5985°C 10 TPW, In R(tpw), a10

0°C to 29.7646°C 11 TPW, Ga R(tpw), a11

温度范围：-189.3442°C to 961.78°C


固定点的实现


水三相点


准备冰套

• Fill well with crushed, solid CO2

• Insert metal rod, pre-cooled in liquid N2

• Pour liquid N2 into well

• Use the “quick Stick” immersion freezer

Dry ice or Liquid N2

• 在做冰套前要预冷水三相点坪

Water

Steel Wire

Cotton Ball

Ice

“Quick Stick”

Immersion Freezer Freezing an Ice

Mantle Using LN2


水三相点瓶的保存

用碎冰保存Crushed ice:

• Drain water and add ice every day

• May have a lifetime up to three weeks

• Do not allow ice to freeze across top

用恒温槽保存 Liquid bath (Fluke 7312 and 7012 bath)

• Maintain temperature: 0.004°C to 0.007°C

• May have a lifetime up to two months


保存水三相点瓶用的恒温槽

Model 7012 7312

Range -10 ~110 C -5 ~110 C

Stability ± 0.0008 C ± 0.001 C

Uniformity ± 0.003 C ± 0.003 C

Accommodation 4 2

TPW Duration 6 weeks 6 weeks


检查水三相点瓶

• 固-液-气三相界面界面;

• 插入室温玻璃棒形成内溶层;

• 使用前检查冰套。冰套应能在瓶内自由旋转;

• 中心温度计插入孔和冰套之间的间隙不能太大（熔化太多）;


其它一些注意事项

• 避免辐射 Avoid IR and visible radiation

• 预冷SPRT Pre-cool SPRT before insertion

• SPRT的自热效应 Self-heating effect

• 静压修正 Hydrostatic pressure effect

• 同位素修正


静压修正

t C Bl

BC

m

0 01

7 10 4

.

.3


同维素修正

• For precipitation (meteoric waters), approximate relationships are

D=8*18O+0.01, and 1+17O = (1+18O)0.528. Therefore, the

temperature correction can be predicted from measurements of D only

according to:

(Tsample - TV-SMOW) µK = 712 X D – 0.8


金属固定点


Fixed point % Purity Quantity (kg) Immersion (cm)

Ga MP 99.99999 0.45 15

In FP 99.9999+ 0.97 18

Sn FP 99.9999+ 0.96 18

Zn FP 99.9999+ 0.95 18

Al FP 99.9999+ 0.35 18

Ag FP 99.9999+ 1.35 18

Au FP 99.9999+ 2.50 18

Cu FP 99.9999+ 1.20 18

金属固定点的一些特性值


Fixed point Equipment

Temperature

Uniformity (°C)

Ga MP 7011 bath 0.001

In FP 9114 furnace 0.01

Sn FP 9114 furnace 0.01

Zn FP 9114 furnace 0.02

Al FP 9114 furnace 0.03

Ag FP 9115 furnace 0.05

保存金属固定点的设备


温度梯度检查

• 在升温熔化固定点前，炉子的温度梯度必须满足要求，否则固定点有可能

破裂。

• 炉子的纵向温度梯度应定期检查，最少每六个月检查一次。

• Fluke的9114炉子（铟点，锡点，锌点，铝点）是三区控温，温度梯度可

以通过调节顶部和底部加热器来完成。

• 9115 和9116炉子是钠管炉，温度梯度很好，不需要调节温度梯度。

Warning!!!


炉子纵向温场检查方法

• 将固定点装入炉子;

• 将炉子温度设定在比熔化温度低5°C;

• 当炉子温度达到设定点后至少等待4

个小时以便炉子温度稳定;

• 将SPRT从底部每提升20mm测试一

次，等待2分钟，再测试下一个点，

直到120mm处，然后以20mm的间

隔向下测试直到底部。每一个点取

两次测量的平均值。


0.4

0.3

0.2

0.1

0

2

3

2

1

4

4

5

6

–0.1

–0.2

–0.3

–0.4

Height (inches)

Tem

per

ature

Dif

fere

nce

(°C

)炉子温场调试 at 662°C


• 将炉子温度设定在比熔点高2°C 过夜。

• 以0.1°C / min的降温速度将炉子降到比凝固点低 2.0 °C.

• 温度开始回升后，将两根室温石英玻璃棒（管）顺序插入到固定点中进行诱

导，每根2 分钟。

• 诱导结束后，将炉子温度设定到比凝固点低0.25 - 0.4°C. 对银点推荐使用

0.25°C，其它固定点0.4°C.

固定点的复现(In, Zn, Al, Ag cells)


• 将炉子温度设定在比熔点高2°C过夜.

• 以0.1°C / min的降温速度将炉子温度降到 2.0 °C.

• 从炉子底部吹入少量压缩空气直到温度开始回升。吹气时间大约2分钟。

• 温度回升后，按顺序插入两根室温石英棒进行诱导，每根2分钟。

• 将炉子温度设在比凝固点低 0.4°C.

锡点的复现


铟点和锡点的典型凝固曲线

Freezing Plateau of Indium Fixed-Point Cell

(Model: 5904, S/N: In-04035)

0.410224

0.410225

0.410226

0.410227

0.410228

0.410229

0.410230

0.410231

0.410232

0.410233

0.410234

7/27/06

16:00

7/27/06

20:48

7/28/06

1:36

7/28/06

6:24

7/28/06

11:12

7/28/06

16:00

7/28/06

20:48

Time and Date of Testing

Bri

dg

e R

ead

ing

(R

t/R

s)

Freezing Plateau of Tin Fixed-Point Cell

(Model: 5905, S/N: Sn-05060)

0.478417

0.478418

0.478419

0.478420

0.478421

0.478422

0.478423

0.478424

0.478425

0.478426

0.478427

8/31/06

10:00

8/31/06

14:48

8/31/06

19:36

9/1/06

0:24

9/1/06

5:12

9/1/06

10:00

9/1/06

14:48

9/1/06

19:36

9/2/06

0:24


Bri

dg

e R

ea

din

g (

Rt/

Rs

)

Freezing plateau of In-04035 Freezing plateau of Sn-05060


锌点和Al点的凝固曲线

Freezing plateau of Zn-06066 Freezing plateau of Al-07093

Freezing Plateau of Zinc Fixed-Point Cell

(Model: 5906, S/N: Zn-06066)

0.629399

0.629400

0.629401

0.629402

0.629403

0.629404

0.629405

0.629406

0.629407

0.629408

0.629409

9/15/06

17:09

9/15/06

21:57

9/16/06 2:45 9/16/06 7:33 9/16/06

12:21

9/16/06

17:09


Bri

dg

e R

ead

ing

(R

t/R

s)

Freezing Plateau of Aluminum Fixed-Point Cell

(Model: 5907, S/N: Al-07093)

84.7608

84.7609

84.7610

84.7611

84.7612

84.7613

84.7614

84.7615

84.7616

84.7617

84.7618

8/14/06 17:15 8/14/06 22:03 8/15/06 2:51 8/15/06 7:39 8/15/06 12:27


Brid

ge R

ead

ing

(R

t/R

s)


Ag点的典型凝固曲线

Freezing plateau

of Ag-08040

Freezing Plateau of Silver Fixed-Point Cell

(Model: 5908, S/N: Ag-08040)

1.073008

1.073009

1.073010

1.073011

1.073012

1.073013

1.073014

1.073015

1.073016

1.073017

1.073018

2/3/06

15:30

2/3/06

20:18

2/4/06

1:06

2/4/06

5:54

2/4/06

10:42

2/4/06

15:30

2/4/06

20:18


Bri

dg

e R

ead

ing

(R

t/R

s)


诱导方法对温坪的影响

Time (hours)

W(Z

n)

2.568675

2.568680

2.568685

2.568690

2.568695

2.568700

0 5 10 15 20 25 30 35

Fused silica rods

Fused silica tubes

1.4 mK

Freezing plateau of sealed fused-silica-cased zinc FP cell (model Zn-5906) using two different

induction methods: fused silica tubes (2+3 minutes and fused silica rods (2+3) minutes.


Freezing plateau of metal-cased tin cell (model Sn-5945) induced by two different mehtods (a), blow

compressed air, two quartz tubes, 4 minutes each; (b). quartz rods (2 + 2 minutes).

1.892632

1.892638

1.892644

1.892650

1.892656

1.892662

0 10 20 30

Time (hours)

W(S

n)

Compressed air

Cold quartz rods

1.6 mK

诱导方法对锡点温坪的影响


Freezing plateau of a fused-silica cased silver cell with different durations of induction

(A: 2 minutes, B: 3 minutes, C: 4 minutes).

4.286285

4.286295

4.286305

4.286315

4.286325

0 6 12 18 24

Time (hours)

W(A

g)

B

C

A

A

B

3.6 mK

不同诱导方法对银点温坪的影响


Freezing plateau of a fused-silica cased silver cell at different furnace temperatures (0.3 K,

0.45 K, and 1.2 K below freeze).

4.286305

4.286310

4.286315

4.286320

4.286325

4.286330

4.286335

0 5 10 15 20 25

W(A

g)

Time (hours)

1.2 K

0.45 K

0.3 K

1.8 mK

不同保温温度对Ag点温坪的影响


金属纯度分析

A

xTTT 0Purity Calculation:

x: the mole-fraction impurity concentration, A: the first cryoscopic constant

84.7611

84.7612

84.7613

84.7614

84.7615

84.7616

84.7617

84.7618

84.7619

84.7620

84.7621

10/6/2006

9:45

10/6/2006

14:33

10/6/2006

19:21

10/7/2006

0:09

10/7/2006

4:57

10/7/2006

9:45

8 mK

10 mK

20 % 50 % 70 %

TT0


固定点的不确定度评估

Source of uncertainties Uncertainty Components (mK)

Tin fixed-point system Zinc fixed-point system

Resistance reading (A) 0.041 0.059

Reproducibility (A) 0.200 0.300

Total A 0.204 0.306

Impurities (B) 0.304 0.541

Hydrostatic correction (B) 0.022 0.027

Pressure correction (B) 0.010 0.013

Immersion (B) 0.040 0.040

SPRT self heating (B) 0.030 0.030

Propagated from TPW (B) 0.050 0.080

Bridge non-linearity (B) 0.020 0.029

Total B 0.314 0.551

Total standard uncertainty 0.374 0.630

Expanded uncertainty (k=2) 0.748 1.260


问题 ?

1. 为什么使用固定点来检定温度计？

2. 使用固定点时可以使用熔化温坪替代凝固温坪吗?

3. 复现固定点的凝固温坪的步骤是什么？


第二部分：

铂电阻温度计


铂电阻温度计

•标准铂电阻温度计 (SPRT)

•铂电阻温度计的常见误差

•如何正确使用铂电阻温度计


• Very pure metals exhibit an almost linear increase in resistance with increasing temperature due to phonon scattering of electrons

• 对于很纯的金属，由于电子的声子散射效应，其电阻值随温度接近线性增加。

0

1

2

3

4

5

-200 0 200 400 600 800 1000 1200

Temperature (癈 )

R(t

)/R

(0 癈

)

Actual Pt

Linear

Temperature vs. Resistance Ratio温度与电阻比值


SPRT 标准铂电阻温度计

• Interpolating instrument over a very wide range

• 一个大温度范围内的插值仪器

– From –259.3467 ºC to 961.78 ºC (ITS-90)

• Most accurate thermometer 最准确的温度计

– Uncertainty: a few millikelvin or better

– 不确定度：几个毫开尔文或更好

• Preferred for high-accuracy temperature measurement

• 适用于高精度温度测量

• Reference standard to calibrate other thermometers

• 校正其它温度计的参考标准


SPRT 标准铂电阻温度计

• Use resistance ratio, W(T90) = R(T90) / R(273.16 K

使用电阻比，W(T90)=R(T90)/R(273.16K)

– Ratio is independent of the Ohm

– 比值独立于Ohm值

• High and low temperature reference functions, W r

• 高温和低温参考函数，Wr

• Defines “ideal behavior” for an SPRT

• 定义一支SPRT的“理想行为”

• Deviation function, W(T90) = W(T90) - W r(T90)

• 偏差函数，W(T90)=W(T90)-Wr(T90)

– Defines “specific behavior” for a calibrated SPRT

– 定义一支检定SPRT的“具体行为”


Characteristics of an SPRTSPRT的特点

REQUIREMENTS 要求 Stability 稳定性 Reproducibility 重复性 Measurability 可测量性

DESIGN FEATURES 设计特征 Strain-free, well-annealed wire 无应变，充分退火 Pure platinum 纯铂丝 Protection from contamination 防污染保护 Four-lead construction 四线结构 Good electrical insulation 良好的电绝缘性 Standard dimensions 标准尺寸

AS A RESULT, SPRTs 结果，SPRTs

Are precise 准确 Are fragile 易坏 Have relatively large-sized resistors 相当较大的电阻 Have relatively low-valued resistors 相对较低的电阻值


Basic Requirement for an SPRTSPRT的基本要求

• An acceptable SPRT, “must be made from pure, strain-free platinum”

• 一支可接受的SPRT“必须由纯的无应变的铂丝制成”

• It, “must satisfy at least one of the following two relations”:

• 它“必须满足至少下面两个条件中的一个”：

W (29.7646°C) 1.11807

W (–38.8344°C) 0.844235

• SPRT up to 961.78°C 如果SPRT使用到961.78°C

W (961.78°C) 4.2844

• The purity of Pt is 99.99% + 铂丝的纯度要达到99.99%+


Three Types of SPRTs 三类SPRTs

Capsule SPRT

套管式SPRT

Long-stem SPRT

长杆SPRT

HTSPRT

高温SPRT

Range范围 13.8 K ~ 273.15 K –189 °C ~ 660 °C 0 °C ~ 962 °C

R( tp) 25.5 ohm 25.5 ohm 0.25 or 2.5 ohm

Typical Size

典型尺寸5 x 50 mm 7 x 520 mm 7 x 680 mm

Sheath外管 Pt or Glass Quartz or Inconel Quartz

Filling Gas

填充气体 Helium Gas Mixture Gas Mixture

Sensor Wire

传感器丝0.07 mm 0.07 mm 0.4 or 0.2 mm


SPRT Sensor Construction SPRT传感器结构

• ITS-90 states, “An acceptable platinum resistance thermometer must be made from

pure, strain-free platinum.”

• ITS-90说明“一支可接受的铂电阻温度计必须由纯的，无应变的铂制成”

• The platinum wire used for sensors is “hard drawn,” as it is somewhat easier to

handle in this condition. It is annealed after the resistor is formed.

• 用于传感器的铂丝是冷拔丝，因为铂丝在这种条件下比较容易加工处理。铂电阻丝制成后进行退火处理。

• The support is well designed to keep the sensor wire strain as low as possible

during vibration, mechanical shock, and thermal expansion and contraction.

• 骨架应精心设计以使传感器丝在遇到震动，机械冲击，热膨胀和收缩时产生的应变尽可能小。

• After an SPRT is made, its sensor must be fully annealed to remove strain.

• SPRT制成后，传感器丝必须充分退火以去除应变。


Construction of an SPRT SPRT的结构


Construction of a Metal-Sheathed SPRT 金属保护管SPRT的结构


Construction of a Capsule SPRT套管式SPRT的结构


Construction of a High Temperature SPRT 高温SPRT的结构


Platinum Resistance Thermometer Equations 铂电阻温度计方程

13.8033 K to 961.78 °C

Reference function defined by ITS-90

参考函数在ITS-90中定义

9090r90 TWTWTW

16.27390

R

TRTW 90TW

90r TW

Deviation function

偏差函数


• Deviation function for Low Temperature Range

• 低温范围的偏差函数

• 7 parameters determined by calibration (a, b, c1- c5)

• 通过检定确定七个参数 (a,b,c1 - c5)

• 7 fixed points used as calibration temperatures

• 七个固定点用于检定温度

- e-H2, Ne, O2, Ar, Hg TPs, plus 2 e-H2 VPs

• Deviation function for sub-range of 83.8K to 273.16K

• 在子温度区间83.8K到273.16K之间的偏差函数

25

1

90

2

90

90909090

])([ln

]1)([

]1)([)()()(

i

i

i

r

TWc

TWb

TWaTWTWTW

SPRT―13.8033 K to 273.16 K

)(ln]1)([]1)([)()()( 909090909090 TWTWbTWaTWTWTW r


• Deviation function for High Temperature Range

• 高温范围的偏差函数

• 4 parameters determined by calibration (a, b, c, d)

• 通过检定来确定四个参数(a,b,c,d)

• 4 fixed points used as calibration temperatures

• 四个固定点用于检定温度

- freezing points of Sn, Zn, Al, Ag 固定点Sn,Zn,Al,Ag.

2

90

3

90

2

90

90909090

)]C323.660()([

]1)([

]1)([

]1)([)()()(

WTWd

TWc

TWb

TWaTWTWTW r

SPRT―0 ºC to 961.78 ºC


0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 500 1000T 90

Wr

Low T Reference

High T Reference

ITS-90 SPRT Reference Functions ITS-90 SPRT 参考函数


SPRT Reference Function13.8033 K to 273.16 KSPRT参考函数 13.8033K到273.16K

Inverse Function 反函数

Reference Function 参考函数

12

1

900r

5.1

5.116.273lnln

i

i

i

TAAW

i

i

i

WBB

T

15

1

61

r0

90

35.0

65.0

16.273


Inverse Function 反函数

Reference Function 参考函数i

i

i

TCCW

9

1

900r

481

15.754

9

1

r090

64.1

64.2

i

i

i

WDDt

SPRT Reference Function 0ºC to 961.78ºCSPRT参考函数 0ºC 到961.78ºC


SPRT Calibration SPRT检定

• The ITS-90 allows for calibration of SPRTs over a restricted range of temperatures

• ITS-90容许SPRTs在一个限制的温度范围内的检定

• Each of these subranges uses a different family of calibration points

• 每一个子温度区间使用一组不同的检定点

• Each has a different deviation function

• 每一个子温度区间有一个不同的偏差函数

• Triple point of water always required

• 水三相点总是需要的


Fixed Points and Sub-Ranges of ITS-90ITS-90的固定点和子区间


SPRT Advantages and Disadvantages

SPRT的优点和缺点

• Advantages 优点

Interpolating instrument of ITS-90 ITS-90的插值仪器

Very wide range 十分宽的温度范围

Highest stability, reproducibility, and accuracy

最高的稳定性，可重复性和准确度

• Disadvantages 缺点

Very fragile 易损坏

Relatively large-sized resistors 相对大尺寸的电阻

Relatively low-valued resistors 相对小的电阻值


Secondary PRT 二级铂电阻PRT

• A durable and accurate sensor

• 耐用和准确的传感器

• Uncertainty and stability are lower than that of an SPRT

• 不确定度和稳定性比SPRT要低

• Typically used in the lab, but suitable for use in the field

• 一般用于实验室，也可用于现场

• Also used as reference for calibration industrial PRTs

• 也可用于检定工业PRTs的参考标准


• The sensor in a secondary PRT adopts a partial strain-free design.

• 二级PRT的传感器容许部分无应变的设计

• The sensor wire is first wound into a small-diameter coil. The coil is then woundonto the fused-quartz-glass cross support, alumina spool, or inserted into a four-bore alumina tubing.

• 传感器丝首先绕成小直径的线圈。线圈再绕到石英十字骨架，陶瓷骨架，或放入四孔陶瓷管。

• A special powder mixture is usually filled into the sensor capsule to support theelement wire to protect the element from mechanical shock.

• 一种特殊的粉末混合物常常用于填入到传感器套管中支撑传感器丝，保护传感器丝不受机械震动的破坏。

• Due to this compromising design, the stability of a PRT is somewhat poorer thanthat of an SPRT, but its ability to handle mild mechanical shock is much better.

• 由于这种妥协性的设计，PRT的稳定性要比SPRT差一些，但适应轻微机械震动的能力要好一些。

Secondary PRT Sensor Construction二级PRT传感器的结构


Sensor construction 传感器结构


Secondary PRT 二级PRT


Calibration 检定

• Mini-fixed point cells 小型固定点

• Comparison using bath 用恒温槽比较法检定


Calculation 计算

• If α = 0.003925 or W (Ga) ≥ 1.11807

use ITS-90 interpolation formula

使用ITS-90内插公式

• If α = 0.00385, use IPRT formula 使用IPRT公式

• If α = 0.00385, you could use ITS-90 interpolation formula as

well

• 如果α = 0.00385, 也可以使用ITS-90内插公式


Characteristic of IPRT IPRT特点

REQUIREMENTS 要求 Rugged 结实 Useable in harsh environments 能用于各种恶劣环境 Interchangeability 可置换 Easy measurability 容易测量 Wide applicability 用于范围广 Low cost 成本低

DESIGN FEATURES 设计特点 Rigid mounting 硬固定 Encapsulated resistor 电阻丝封装 Two-lead construction 两线结构 Large-valued resistance 电阻值大 Small-sized resistor 电阻丝体积小 Many configurations 多种结构

AS A RESULT, IPRTs 结果 Are less stable than SPRTs 没有SPRTs稳定 Have greater measurement error 有较大的测量误差 May exhibit hysteresis effects 有滞后效应


Construction of IPRT IPRT的结构


Calibration of IRT

工业电阻温度计的检定

Comparison with calibrated SPRT over limited

ranges is stirred liquid or solid baths.

在液体搅拌槽或比较块炉中,在一定范围内与分度过的标准铂电阻温度计比较检定

Rely on manufacturer’s calibration.

利用生产厂家的检定结果

Calibration in vicinity of thermometric fixed points.

在温度固定点温度的附近温度检定


• Historically, the temperature dependence of the platinum resistivity was recognized to be well described by a simple quadratic equation

• 历史上一个简单的二次方程被公认为可以用来很好的描述铂的电阻系数和温度的关系

– The Callendar – Van Dusen equation:

– where

))100

1(100

1(

)1()C0()(

0

20

tttR

BtAtRtR

0

0100

100 R

RR

Calibration and Calculation 检定和计算


• Temperature coefficient: 温度系数：

• The value of is often used as an indicator of the purity of the platinum, with larger values corresponding to higher purity.

的值经常被用来作为铂丝纯度的一个指标，较大的值对应较高的纯度

– For a typical SPRT: = 3.925 10-3 Ω/Ω/°C

– For a typical IPRT: = 3.85 10-3 Ω/Ω/°C

0

0100

100 R

RR

Or α=(R100/R0-1)/100



• An additional term is required to adequately describe the R

versus T relationship below 0 °C

• 对于0 °C以下的温度范围，须用一个额外的项来描述R与T的关系

– The Callendar - Van Dusen equation:

– where

C = 0 for t > 0 °C.

))100(1()( 320 ttCBtAtRtR



• This graph shows the reference functions for a Standard IPRT and the ITS-90 SPRT.

• 这个图显示标准IPRT和ITS-90 SPRT的参考函数

0

1

2

3

4

-200 0 200 400 600 800

Temperature (癈 )

R(t

)/R

(0 癈

)

ITS-90

IEC-751

ASTM E 1137-96 / IEC-751 StandardASTM E 1137-96/IEC-751标准


Advantages and Disadvantages

优点和缺点

• Advantages 优点

Rugged 结实

Useable in harsh environments 可用于恶劣环境

Wide applicability 宽的应用范围

Low cost 成本低

Interchangeability 可交换

• Disadvantages 缺点

Less accurate than SPRT 比SPRT精度低

Less stable than SPRT 没有SPRT稳定

Hysteresis effect 热滞效应


Common Errors in Platinum Resistance Thermometry 铂电阻温度计的常见误差

• Mechanical Shock and Vibration 机械振动

• Thermal Shock 热振动

• Contamination 污染

• Hysteresis 热滞效应

• Oxidation 氧化

• Leakage 泄漏

• Immersion Errors 浸没误差

• Radiation Errors 辐射误差

• Self-heating 自热

• Lead Resistance Errors 引线电阻误差

• Others 其它


Mechanical Shock and Vibration 机械振动

• They are main contributors to long-term drift in PRTs

• 这是PRTs长期漂移的主要因素

• Rapid acceleration of the thermometer will cause unsupported wire to flex

against the supports or substrate

• 温度计的快速移动会造成没有支撑部分的电阻丝围绕骨架或基体变形

• Metal sheathed PRTs with partially supported elements used in laboratory

applications should be treated as fragile instruments despite their robust

appearance

• 在实验室使用的部分支撑金属保护套管PRTs尽管外观上看很结实，但应当像使用易坏仪器一样小心

• In high-vibration industrial applications, fully supported PRTs should be used

• 在高振动的工业应用中，应当使用完全支撑的PRTs

• Mechanical shock could damaged any SPRT/PRT

• 机械振动可能会损坏SPRT/PRT

• The resistance at TPW should be tracked

• 温度计的TPW值应当跟踪记录


Mechanical shock 机械振动

Shorted sensors due to mishandling or shipping

由于误操作或运输过程造成的电阻丝短路


Thermal Shock 热振动

• Cooling a thermometer rapidly from high temperatures to room

temperature can quench excess lattice-site vacancies in the

platinum crystal structure

• 将温度计从高温快速冷却到室温，高温下产生的过量晶格空位将

会被淬火固定在室温下的铂晶格中

• The R(tp) of the thermometer would increase

• 温度计的R(tp)值将会升高


Contamination污染

• If a thermometer be contaminated, the R(tp) would increase, and the W(Ga)

would decrease. W(Ga) might not meet the requirement of ITS-90 anymore

• 如果一支温度计被污染，R(tp)值将会升高，W(Ga)值将会降低。W(Ga)值有可能不再满足ITS-90的要求。

• Metal vapors diffuse through the fused silica tube at high temperature

• 金属蒸气在高温时扩散到石英管中

• PRTs with fused quartz sheaths exposed at high temperatures in furnaces with a

metal block can be easily contaminated by metal vapors.

• 如果石英保护套管PRTs放置在有金属块的炉子中在高温下很容易被金属蒸汽污染

• PRTs with metal sheaths at high temperatures, the element could be

contaminated by the metal sheath

• 金属保护套管PRTs在高温下，电阻丝有可能被金属管污染


Contamination example 被污染的例子

0

20

40

60

80

100

120

140

0 100 200 300 400 500 600 700 800

Total hours at 1100°C in different blocks

R

tp/R

tp (

1e-6

)

#80136 in graphite #79506 in Ni-Cr #79506 in graphite

#79525 in Ni-Cr #79536 in graphite #79536 in Ni-Cr

5 mK


Annealing 退火

• Annealing can reverse effects of minor

strain and oxidation.

• 退火可以消除小的应变和氧化

• Anneal at the maximum operating

temperature of the thermometer, between

550°C to 660°C if possible.

• 应在温度计的最大使用温度下退火。如果可能

的话，在550°C至660°C之间

• The block should be of a non-

contaminating material such as graphite or

alumina. Keep the thermometer sheath

clean.

• 炉子中的温度块应当采用不会造成温度计污染

的材料，如石墨或陶瓷。温度计外管应保持干

净。


Hysteresis 热滞效应

Hysteresis in an Industrial PRT.

-0.060

-0.040

-0.020

0.000

0.020

0.040

0.060

-100 0 100 200 300 400 500 600 700

Temperature, °C

Hyste

resis

Err

or,

°C

Hysteresis

The hysteresis error is proportional to the temperature range covered

热滞效应误差与所涵盖的温度范围成正比


Hysteresis 热滞效应

• Very little hysteresis could be detected in an SPRT

• 很小的热滞效应误差就可以在SPRT中被检测出来

• Less than 10 mK hysteresis could be found in secondary PRT

• 小于10mK的热滞效应误差可以在二级PRT中被检测出来

• A typical hysteresis in a fully supported PRT ranges between

±0.02% and ±0.05%, and depends on the range.

• 对完全支撑型的PRT，典型的热滞效应误差在±0.02% 到 ±0.05%

之间，具体的大小决定于使用的温度范围。


Hysteresis Evaluation 热滞效应评估

Temperature range 温度范围

Low end 低端 High end 高端Mid point 中点

Thermometer

Measured

温度计测量结果

Thermometer

Measured

温度计测量结果

Δt


Platinum Oxidation Effects 铂丝氧化效果

• Oxygen Protects Platinum from Contamination

• 氧气可以保护铂丝不被污染

– Oxygen can help stabilize the trace oxide impurities in the platinum and in the

sensor support, thus preventing the solution of free impurity ions in the platinum

at high temperature.

– 氧能稳定铂丝和骨架中的微量氧化物杂质以阻止自由的杂质离子在高温时溶入到铂丝中

• In the 1970s, Berry discovered platinum oxidation effects over the range of 0 – 450°C

• 1970年代，Berry发现了0-450°C温度区间的铂的氧化效应

• Pt oxide film will grow on the surface of Pt wire in the range of 0 – 450°C when as

little as 5 kPa of oxygen is present

• 在0-450°C温度区间和低至5kPa的氧分压时，铂的氧化物薄膜将在铂丝表面生长


Platinum Oxidation Effects 铂的氧化效应

• The resistance of Pt wire increases because part of its cross-sectional area is

replaced by a poorly conducting oxide film

• 由于铂丝的部分横断面被弱导电性的氧化物薄膜替代，导致铂丝的电阻值升高

• Two basic types of Pt oxidation: 2d and 3d

• 铂丝的两种基本氧化类型：两维氧化和三维氧化

• A 2d Pt oxidation will grow from 0°C to 300°C, and dissociate above about 450°C.

The maximum change in resistance is about 8 ppm (~2 mK).

• 铂的两维氧化物在0-300°C温度区间生长。当温度超过450°C时，两维氧化物分解。最大的电阻变化是大约8ppm(~2 mK)

• 3d Pt oxidation will occur from 300°C to 500°C, and dissociate above about

550°C. A change in resistance of 430 ppm (~0.1°C) was observed from such

oxidation effect.

• 三维氧化发生在300-500°C温度区间。当温度超过550°C时，三维氧化物分解。这种氧化会导致电阻变化430ppm (~0.1°C)。


Platinum Oxidation Effects 铂的氧化效应

• Resistance drift at lower temperatures (excluding mechanical shock) is

mainly from oxidation.

• 低温时的电阻漂移主要来自于氧化（除了机械振动）

• Oxidation is largely reversible and tends to dissipate above 500°C.

• 大部分氧化都是可逆的。当温度高于500°C时会发生分解

• The effect is repeatable in a fused-quartz-glass SPRT.

• 对石英保护套管SPRT，氧化效应是可重复发生的

• Less repeatable in a metal-sheathed SPRT or PRT, diminishing over

time as oxidation of the sheath metal removes oxygen from the fill gas.

• 对金属保护套管SPRT或PRT，氧化效应的重复性要弱一些。随着金属保护套管逐渐消耗充入的氧气，这种氧化效应的重复性会逐渐减弱


Oxidation Examples 氧化的例子

2D oxidation

25.5320

25.5320

25.5321

25.5321

25.5322

25.5322

25.5323

25.5323

0 100 200 300 400 500 600

Hours

R(t

pw

), o

hm

600°C 600°C420°C600°C232°C

1 mK

3D oxidation


Evaluation on Oxidation Effects 评估氧化效应

• Depends on operation temperature range

• 决定于使用温度范围

• Stabilize the oxidation at a specific temperature

• 在某一个特点温度下稳定氧化物

• Understand different thermometer may have different oxidation effects

• 需要理解不同的氧化物有不同的氧化效应

• Track the R(tpw), which is dependent on the thermal history of the thermometer

because of the oxidation state of the platinum

• 跟踪R(tpw)值。由于铂的氧化状态，R(tpw)值决定于温度计的使用历史

• Measure R(tpw) of the thermometer in the same oxidation state as the other

temperature measurements

• 在和别的温度测量相同的氧化状态下测量温度计的R(tpw)值


Gas Leakage 气体泄漏

• Damaged seal 密封损坏

• Ingress of moisture 水蒸气进入

• Excess the oxidation due to room air leak into the sheath

• 由于大气进入到保护套管加速了铂丝的氧化


Insulation Resistance 绝缘电阻

• Electrical leakage between leads or between leads and the sheath can introduce

significant measurement errors

• 引线之间或引线与保护套管之间的漏电可能导致明显的测量误差

• It is pretty simple to measure the leads-to-sheath insulation resistance of a metal-

sheath thermometer

• 测量金属保护套管温度计的引线和保护套管之间的绝缘电阻很简单

• It is not necessary to measure the leads-to-sheath insulation resistance of a

glass-sheath thermometer

• 没必要测量玻璃保护套管温度计的引线和保护套管间的绝缘电阻

• As a user, it is impossible to measure insulation resistance between leads of

metal-sheathed or glass-sheathed thermometers

• 作为用户，测量金属保护套管或石英保护套管温度计的引线之间的绝缘电阻是不可能的


Insulation Resistance 绝缘电阻

• In a thermometer, besides the PRT sensing resistor, there are many insulation resistances that are parallel connection to sensing resistor. Those insulation resistances are between the leads, insulation material, sensor support, filling material, etc.

• 在温度计中，除了PRT传感器电阻，还有许多绝缘电阻并联在传感器电阻上。这些绝缘电阻包括引线之间的电阻，绝缘材料，传感器骨架，填充材料等

• Not fully contribute to the errors, since they existed during calibration

• 因为这些电阻在温度计检定时已经存在，所以并不是所有这些电阻都会造成测量误差。

• The errors come from the insulation resistance changing at same temperature

• 误差来源于这些绝缘电阻在同一温度时的变化

• The worse case will be: ΔR = Rt*RI / (Rt+RI) – Rt

• 更坏的情况是：ΔR = Rt*RI / (Rt+RI) – Rt


Immersion Errors 浸没深度误差

• Insufficient immersion of the thermometer can create a temperature gradient through temperature sensing element that may generate an error

• 温度计的浸没深度不够可能会造成沿着温度计传感器的温度梯度，从而产生测量误差

Heat


Immersion Errors 浸没深度误差

Comparison of Immersion Effects of Different Thermometers, 420°C

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Immersion, cm

Te

mp

era

ture

De

via

tio

n, °C

150mm immersion

100mm immersion

125mm immersion


Immersion Error Evaluation评估浸没深度误差

• To test the adequacy of immersion, change the immersion depth. If adequate, the

reading of thermometer will be consistent

• 为了测试合适的浸没深度，改变浸没深度进行测量。如果浸没深度合适，温度计的读数应当是一样的

• Fixed points should show change in T related to hydrostatic head

• 对于固定点的测量，温度随静压的变化应当能够显示出来

• In a bath or dry-block calibrator, the vertical temperature gradient should be

considered

• 对恒温槽或干井，应当考虑垂直温度梯度

• Different thermometer may have different immersion errors

• 不同的温度计有不同的浸没误差


Radiation Errors 辐射误差

• Radiation is one of the most insidious sources of error in thermometry

• 辐射是温度计误差中最隐藏的来源之一

• It is a particular problem in air and surface thermometry

• 在空气和表面温度测量中，辐射误差是个具体的问题

• Incident radiation through ice bath can cause error as much as 0.5 mK

• 冰点槽的辐射可能造成高达0.5mK的误差

• Stirred bath should have radiation shields

• 搅拌的恒温槽应有防辐射保护罩

• Light piping: heat loss from radiation of visible and near infrared radiation up glass

sheath

• 光导：可见光和近红外辐射造成通过石英外壳上部的热损失

• Light piping is greatly reduced by sand-blasting or by coating the sheath with

graphite paint

• 使用磨砂或在石英外管进行石墨镀层可显著减少光导误差


Self-heating 自热

• Electric current through

thermometer causes it to

heat and increase in

resistance

• 电流通过温度计会产生热量，造成电阻升高

RIT

2

Where δ is dissipation constant, mW/ºC


Self-heating Effects 自热效应

• Temperature increase depends on the electric power and on the thermal

conductance

• 温度升高决定于电能和导热性

• A good thermometer design should have

• 一个好的温度计设计应当有

– Maximum radial conductance 最大的径向导热

– Minimum axial conductance 最小的轴向导热

• A thermometer has a fixed “internal” thermal resistance but the “external”

thermal resistance should be minimized by a good thermal contact

• 每支温度计都有一个固定的“内部”热阻，但其“外部”热阻应当通过良好的热接触来最小化


Self-heating Effects 自热效应

• “External” thermal resistance must be made negligible in practice

• 实际使用时必须使得“外部”热阻小得忽略不计

• Internal self heating is NOT an error

• 内部自热不是误差

• Extrapolation to zero current for most precise work

• 对于要求最高精度的测量工作，应当插值外推到零电流时的值

• At low power, self heating is linear

• 在小功率时，自热效应是线性的

• Thermometer measurement current must be same in use as that used in calibration

• 温度计测量电流必须与检定时所使用的电流一样


Self-heating Evaluation 自热效应评估

• The self-heating could be estimated using

• 自热效应可以估算：

• For example 例如:

– 100 Ω sheathed PRT at 0°C 100 Ω 保护管PRT在0°C时

– 1 mA measurement current 1 mA测量电流

– 50 mW/°C dissipation constant provided by manufacturer’s

– 厂家提供50 mW/°C 耗散常数

– specification 规格

RIT

2

CT

002.0

CW05.0

100A001.02


Self-heating Evaluation 自热效应评估

• The corrected temperature (zero-power) could be calculated:

• 校正过的温度(零功率)的计算：

Use to derive Equation 推导方程

When

Zero-power temperature

零功率时温度为

RIT

2

)( 212

22

1

21

10 TTII

ITT

12 2II

210 2 TTT


Lead Resistance Errors 引线电阻误差

Two leads construction

两线结构

RT

RL1

RL2

+

-

RT

RL1

RL2

RL3

+

-

RT

RL2

RL1

RL3

RL4

+

-

Three leads construction

三线结构

Four leads construction

四线结构


Other causes 其它因素

• Grain growth of platinum 铂的晶粒生长– High temperature x time 高温 x 时间

– Changes resistance 电阻改变

– Weakens the wire 铂丝强度变弱

• Thermoelectric effects 热电效应– Reduce it by employing switched DC or AC sensing currents

– 通过交替变换DC或AC传感器电流来减少热电效应

• Electromagnetic Interference 电磁干扰


Proper Use of SPRT/PRT

SPRT/PRT的正确使用

• Measure Rtp frequently and use W(t) 经常测量R(tpw)，使用W(t)

• Mechanical treatment and shipping precautions 在使用和运输过程中小心

• Thermal treatment and annealing 热处理和退火

• Avoid quartz devitrification 避免石英析晶

• Avoid radiation effects 避免辐射效应

• Understand platinum oxidation effect 理解铂丝的氧化效应

• Avoid platinum contamination at high temperature 避免铂丝在高温下污染

• Self-heating effect 自热效应

• Thermometer immersion 温度计浸没深度

• Hydrostatic pressure effect 静压效应


Evaluation of Platinum Resistance

Thermometers

铂电阻温度计的评估


Methods of Evaluation (1) 评估方法(1)

• Evaluation can be based on comparison results from simple

measurements.

• 评估可以基于简单测量的比较结果

• Required equipment: 要求设备

Non-contaminating annealing furnace 无污染的退火炉

Resistance measurement instrument 电阻测量仪器

Triple point of water cell with maintenance bath

水三相点瓶及恒温槽

Melting point of gallium cell and maintenance device, and/or other fixed-

point cells.

嫁固定点的熔化点和维持设备，和/或其它固定点容器



• As part of quality assurance, the R(tpw) of an SPRT or a secondary

PRT should be measured regularly and tracked.

• 作为质量保证的一部分，SPRT或二级PRT的R(tpw)值应当定期测量和跟踪

• If it is found to have drifted, further examination is needed.

• 如果发现有漂移，需要做进一步的检查

• Ideally, the W(Ga) should then be measured. If the melting point of

gallium is not available, other fixed-point cells, such as tin or zinc, may

suffice.

• 理想情况下，W(Ga)值也应当测量。如果实验室没有嫁熔化点设备，也可用其它固定点，比如锡点或锌点来替代



• Check insulation resistance of a metal-sheathed SPRT or PRT by

measuring the resistance between the sheath and any of the leads with

a megohmmeter after the thermometer has been exposed to 0°C or

lower for some time and then returned to room temperature.

• 将温度计置于0°C或更低温度下一段时间，然后放回到室温，使用一个兆欧表检查金属保护套管SPRT或PRT的外保护管和任意一根引线之间的绝缘电阻

• With a fused-quartz-glass SPRT, check for moisture by inserting the

SPRT into a cold bath or container of crushed dry ice for a few hours.

Look for condensation inside.

• 对石英保护套管SPRT，将SPRT插入冷的恒温槽或放有碎干冰的容器中几个小时。查看温度计内的冷凝现象


R(tpw) increases slightly, W changes littleR(tpw)轻微增加，W值少量变化

• Common with SPRTs and PRTs.

• 在SPRTs和PRTs中很常见

• Platinum oxidization or slight

mechanical shock.

• 铂丝氧化或轻微机械振动

• Reversed by annealing.

• 通过退火可以回复

• Monitor R(tpw). Anneal after it

changes significantly (2 mK for an

SPRT).

• 监测R(tpw)值。如果R(tpw)值发生显著变化(对SPRT 2mK)，进行退火处理。

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1/1/05 2/20/05 4/11/05 5/31/05 7/20/05 9/8/05 10/28/05 12/17/05

Date

R(t

pw

), o

hm

0.5 mK annealed

annealed

R(tpw) partial recovery through annealing

通过退火处理R(tpw)值部分回复


R(tpw) increases significantly, W changes little

R(tpw)显著增加，W值少量变化

• Severe oxidation or mechanical shock.

• 严重氧化或机械振动

• If the R(tpw) is restored by adequate annealing, the cause was oxidation.

The thermometer can still be used.

• 如果退火后R(tpw)值被回复，漂移原因是氧化。温度计还可以使用。

• If the R(tpw) only increases more after annealing, the sensor is damaged

and the thermometer should no longer be used; it is likely to continue to

be unstable.

• 如果进一步退火后R(tpw)值进一步增加，说明传感器丝已损坏，温度计不能再接着使用。温度计的不稳定现象会继续发生。


R(tpw) increases slightly, W decreases slightly

R(tpw)值轻微增加，W值轻微下降

• Mechanical shock or slight contamination.

• 机械振动或轻微污染

• After annealing, if the R(tpw) is recovered, the cause is mechanical shock; otherwise, it is contamination.

• 退火后，如果R(tpw)值能够回复，原因是机械振动；否则，说明铂丝被污染

• In the case of mechanical shock, the thermometer can continue to be used, but greater care sure be taken to avoid further mistreatment.

• 如果原因是机械振动，温度计可以继续被使用，但是应当加倍小心以避免更多的错误使用和操作。

• In the case of contamination, the damage is irreversible. Find the source of contamination and eliminate it.

• 如果是铂丝污染，则损坏是不可回复的。找出污染源并除去它。

• A slightly contaminated thermometer might still be usable, but it should be re-calibrated.

• 一支被轻微污染的温度计也许还可以再使用，但是温度计应当被重新检定。


R(tpw) increases significantly, W decreases slightly R(tpw)值轻微增加，W值轻微下降

• Severe mechanical shock.

• 严重的机械振动

• The R(tpw) might be partially restored by annealing.

• 通过退火R(tpw)值可以部分被回复

• Test for stability. 测试稳定性

• Re-calibrate.重新检定

• It might be usable, but with degraded accuracy.

• 可能还可以使用，但是测量精度将会下降

• Prevent further mechanical shock.

• 防止进一步的机械振动

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Measurements

R(t

pw

), o

hm

3 mK

after annealed at 660癈 for 4 hours

5 mK

continue annealing at 660癈

R(tpw) recovery through annealing

退火后R(tpw)值回复


R(tpw) increases significantly, W decreases significantly R(tpw)值显著增加，W值轻微下降

• Significant contamination; R(tpw) may shift more with annealing.

• 严重污染；退火后R(tpw)值可能变化更多

• Find the source of contamination; check other thermometers.

• 找出污染源；检查其它的温度计

• If W(Ga) still meets ITS-90 requirements, the PRT might still be used, after re-calibration. 如果W(Ga)还满足ITS-90的要求，重新检定后PRT还可以继续使用

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Measurements

R(t

pw

), o

hm

2 mK

1.118076

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1.118092

1.118100

1.118108

1.118116

1.118124

1.118132

0 2 4 6 8 10 12 14

Measurements

W(G

a)

2 mK


R(tpw) decreases significantly, W increases

R(tpw)显著下降，W值增加

• Damaged seal, allowing moisture to seep in.

• 密封损坏，水汽渗进温度计

• Check for reduced insulation resistance or condensation inside the

sheath.

• 检查绝缘电阻是否减小或保护管中是否有水汽凝结

• If the seal is questionable, the SPRT should be returned to the

manufacturer for examination.

• 如果密封可疑，SPRT应当被退回给生产厂家进行检查


R(tpw) decreases significantly, unstable

R(tpw)值显著降低，不稳定

• Short circuit between sensor coils caused by severe mechanical shock.

• 由于严重的机械振动造成传感器线圈间的短路

• Test: During the measurement of the triple point of water, slightly shake the handle of the

thermometer. Erratic readings indicate shorted coils.

• 测试：在进行水三相点的测量时，轻微摇动温度计的手柄。如果读数错误，说明传感器线圈短路

• With a fused-silica-sheathed SPRT, the damage might be visible with a magnifying glass, but it

is often not noticeable by the user.

• 对于石英保护套管SPRT，有可能用放大镜可以观察到损坏，但是用户一般看不出来

• An SPRT in such condition is no longer usable.

• 如果这种情形发生，这支温度计不能再使用


R(tpw) decreases continuously with annealing

R(tpw)值随着退火持续下降

• Grain growth of the sensor platinum.

• 铂丝的晶粒生长

• The thermometer might still be usable, but stability could be degraded,

and it will be more sensitive to mechanical shock.

• 温度计可能还可以使用，但是稳定性会下降，同时对机械振动会更敏感

• Avoid further use at high temperatures.

• 避免继续在高温下使用


Summary on PRT EvaluationPRT的评估概要

• Monitor the stability of your thermometers.

• 监测你的温度计的稳定性

• Evaluation can tell when a PRT or SPRT has lost accuracy, what kind of damage

it has received, what the likely causes are, and what actions should be taken. It

might be possible to restore the thermometer to a nearly normal condition.

• 评估可以发现什么时间PRT或SPRT失去了准确度，它受到了何种损坏，可能是什么原因，以及应当采取何种行为。如果采取适当操作，有可能将温度计回复到接近正常状态

• These methods may also be applied to IPRTs.

• 这些方法也可用于IPRTs

• Evaluation of an SPRT or PRT is not just a job for the manufacturer, but also

yours.

• 评估SPRT或PRT不仅是生产厂家的工作，同时也是用户您的工作。


问题?

1. 为什么要定期检查SPRT？检测SPRT稳定性的最简单方法是什么？

2. 如果一支SPRT温度计的R(tpw)值一直向上漂移，但W值向下漂移，可能造成的原因是什么？

3. 如果一支SPRT温度计的R(tpw)值突然显著向下漂移，可能造成的原因是什么？

its-90 fixed points · – melting ice, 冰的熔化 ... -189.3442°c to 0.01°c 4 ar, hg, tpw...

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