Cryogenic lectures @ IIT Bombay

Srinivas VanapalliUniversity of Twente

The Netherlands

Prof. Miko Elwenspoek

Liquid helium in Leiden (1908) 4.2 K

Measurement of Onnes with Mercury (8 april 1911)

Inaugural lecture H.J.M. ter Brake, May

12th, 2011

Measurements in an improved test rig (26 oktober 1911)

suprageleiding

(1913)

Superconductors and Cryogenic cooling in Twente

materialen

“Future Energy Technologies”

Science Society

Energy Materials and Systems

9

Test experiments: experimental setup

Test results (lower pressure, Tcold = 3.15 K)

50

70

90 T cell 2

T HS cell 1

T HS cell 2T (

K)

50

70

90

110 T cell 3

T cell 4

T HS cell 3

T HS cell 4

T (

K)

16.46

16.50

16.54

p high

p (

ba

r)

1.2

1.4

1.6

1.8

p medium

p (

ba

r)

0.24

0.25

0.26

0.27

p low

p (

ba

r)

0

4

8 P heater cell 2

P heater cell 3

P heater cell 4P (

W)

0 10 20 30 40 50 60

3.10

3.15

3.20

T cold

time (min)

T (

K)

All graphs (113) and tables (71) are available on www.researchmeasurements.com

REFERENCE BOOK

• Instrumentation : Why, What, How?

• To check, control or investigate

• Temperature, Pressure and Flow

Cryogenic Instrumentation

• Cryogenic :

• Temperature range

120 K

77 K - Liquid Nitrogen boiling point @ 1 atm

20 K

4 K - Liquid Helium boiling point @ 1 atm

1 K

mK

• Vacuum isolation : vacuum feed through

Temperature scale – Historical quest

60 mm

10 mm

An Example: Joule-Thomson microcooler

60 mm

10 mm

An Example: Joule-Thomson microcooler (2)

T T T T T T T

P

P M

M

P

An Example: Joule-Thomson microcooler (3)

High pressure (nitrogen): 80 bar

Low pressure: 6 bar

Cool down time: 7 min

Cold-tip temperature: 101 K

Measured cooling power: 131 mW

An Example: Measurement results

MIN MAX

OU

TP

UT

PARAMETER

Selection criteria for sensors

- Range:

- Min to max of measurement

- Resolution:

- Smallest detectable difference

- Sensitivity:

- dO/dP

- Uncertainty:

- Precision &Accuracy

- Random & Systematic error

HIGH REPEATABILITY

LOW UNCERTAINTY = HIGH PRECISION + HIGH ACCURACY

HIGH RESOLUTION

LOW NOISE

LOW DISTURBANCES (CROSS

SENSITIVITIES)

HIGH SENSITIVITY

HIGH RANGE ?

LOW SETTLE TIME : 1 MS ?

Selection criteria: uncertainty

Thermocouple : EMF (Electromotive Force)

Capacitor : change in el. capacity

Resistors : change in el. resistivity

Diodes : change in gap voltage

Noise : thermal noise change

Gasbulb : expansion of ideal gas

Cryogenic temperature sensors: Principle, sensitivity

Measurement structure

Metallic resistance thermometers

Semi-conductor like thermometers

Cryogenic temperature sensors: Principle, sensitivity

SOURCE : JACK W. EKIN

Smallest readable change

Cryogenic temperature sensors: Resolution

SOURCE : JACK W. EKIN

PT100

Specimen

PT100/1000

Multimeter

PT100; 2 wire & 4 wire, self-heating

PT100; 2 wire & 4 wire, self-heating

PT100; 2 wire & 4 wire, self-heating

PT100; 2 wire & 4 wire, self-heating

Thermal conductivity of solids

T

V

- Errors in measurement set-up.

- Self heating

- Heat load through wire to sensor

- thermal anchoring

- Heat load wire to system

- thin resistive wires

- 4 point measurement

- Cross talk

- Use twisted wires

- Location: gradients

- Extra heat capacity

- Response time

f

R1

R2 R3

V/I=R1V/I=(R1+R2+R3)

I

R5R4

B

300K

Cryogenic temperature sensors: errors

Gas supplyPressure sensors

Vacuum chamber

Feedthrough

Temperature

sensor

Heater

Best practices!

Thermal anchoringTwisted cables

Shielding + 4 point

Thick lines

to heater

Glue or firmly

attach sensors

Diaphragm

wheatstone bridge

STRAIN GAUGES / PIEZO RESISTORS

Temperature

compensated !

PRESSURE SENSORS

Pressure sensors principle

Temperature

compensated !

Pressure sensors principle

Bara Barg Bar

Psia Psig Psi

Pressure sensors: selection type

Pressure sensors: vacuum range

Massflow measurement principle: Thermal

Massflow measurement principle: Thermal

http://www.bronkhorst.com/en/products/gas_flow_meters_and_controllers/

Massflow measurement principle: Coriolis

Coriolis Mass Flow Meters/Controllers:

• Flow through vibrating tube

• Changes frequency, phase shift or amplitude.

• Independent of the physical properties of the fluid!

Massflow measurement principle: Coriolis

PID Feed back loop• Temperature control -> heater• Pressure and Flow contol -> control valve

P ACTION ONLY:

PID ACTION :

P= ProportionalI = IntegralD= Derivative

PID control

Measurement structure