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EC410 OXYGEN SENSOR TEST REPORT

CONTENTS

1 Introduction…………………………………………………………………………3

2 Applicable Documents………………………………………………………….…3

3 Performance Test Results

3.1 Stabilisation Test………………………………………………………………3

3.2 Output in air……………………………………………………………………4

3.3 Output in nitrogen……………………………………………………………..4

3.4 Pressure Coefficient- High Pressure………………………………………..4

3.5 ‘Fridge’ Temperature Test…………………………………………………...4

3.6 Cross-Sensitivity to hydrogen……………………………………………….5

3.7 Instrument aspirator Tests…………………………………………………..5

3.8 Instrument Pump Tests………………………………………………………5

3.9 Calibration curve & Repeatability……………………………………………6

3.10 Flow Rate……………………………………………………………………6

3.11 Warm-Up time………………………………………………………….… 7

3.12 Response time……………………………………………….……………..7

3.13 Vibration……………………………………………………………….…….7

3.14 Drop Test…………………………………………………………….…… 7

3.15 Orientation……………………………………………………………..… .7

3.16 Temperature…………………………………………………………………8

3.17 Pressure Coefficient Low Pressure…………….….………………………8

3.18 Humidity………………………………………………………………………8

3.19 Air Velocity / Flow……………………………………………………………8

3.20 Poisons…………………………………………………………….…………8

3.21 Physical Properties…………………………………………….……………9

3.22 Effect of Carbon DiOxide………………………………………………9

3.23 Long Term Test …………………………………………………………9

4 Conclusions

Appendix 1 Stabilisation Graphs

Appendix 2 Output in Air / Nitrogen

Appendix 3 Fridge Test Graph

Appendix 4 Cross-sensitivity to hydrogen

Appendix 5 Aspirator & Pump Test Graphs

Appendix 6 Calibration Curve-Linearity Graph

Appendix 7 Repeatability Graph

Appendix 8 Flow Rate

Appendix 9 Response time graph

Appendix 10 Vibration Graphs

Appendix 11 Drop Test Graphs

Appendix 12 Orientation Data

Appendix 13 Temperature Performance graphs

Appendix 14 Low Pressure Response Graphs

Appendix 15 Response to Humidity Graphs

Appendix 16 Effect of Carbon di Oxide

Appendix 17 Long Term Test

1 Introduction

This report details the performance of the EC410 Oxygen sensor relative to the e2v Oxygen sensor performance test plan (AD1).

This type of electrochemical sensor has a different mode of operation compared to the galvanic sensors in common use. The main difference is that the EC410 sensor has no sacrificial Anode and as such does not have a limited life. The sensor works as an Oxygen ‘pump’, taking in Oxygen from the test atmosphere and reacting it with protons (in the solid electrolyte) on the working electrode (held at a potential of +600 mV) to form water and producing a current. The other half reaction, on the counter electrode involves the breaking down water to form Protons and Oxygen.

2 Applicable Documents

AD1 Electrochemical Oxygen Sensor Test Plan -..\..\Oxygen Sensors\Documents\Oxygen Sensor - Performance Test Plan.doc

AD2

Performance Requirements for Instruments to Detect Oxygen ..\..\..\..\standards\europe\bsen50104.pdf

3 Performance Test Results

3.1 Stabilisation in Air

see Appendix 1 for Stabilisation profile

 

Initial Plateau

Stabilisation Profile

 

 

 

Voltage / V

Time / Secs

Final Output /mV

t90 Down Output / mV

90% Time from Plateau /secs

Sensor 1

4.390

44

334.0

739.62

8

Sensor 2

4.753

30

354.1

793.92

10

Sensor 3

4.788

26

361.5

804.15

8

Sensor 4

4.795

44

357.5

801.27

12

Sensor 5

4.801

34

354.5

799.11

10

The overall stabilisation time consists of 2 distinct profiles, an initial plateau stabilisation time, in which the Oxygen pump is set up, followed by a logarithmic

3.1 Stabilisation time (Cont.)

type decay as the sensor current flow stabilises (possibly by consuming the initial levels of Oxygen within the sensor). In most instruments, which run this type of 3-electrode electrochemical sensor, the circuitry is set up so that the bias voltage is continuously applied. The power required to do this is not significant

3.2 /3.3Output in Air & Nitrogen (at room Temperature)

see Appendix 2 for typical profile

 

Initial Output in air / -mV

N2 Output in nitrogen /-mV

Sensor 1

328.8

16.7

Sensor 2

350.4

14.2

Sensor 3

330.6

19.4

Sensor 4

321.8

20.6

Sensor 5

324.7

15.6

3.4 Pressure Coefficient High Pressure

The EC410 sensor is only specified to ( 10% of ambient. However the sensor may be suitable for pressure up to 100kPa above ambient. This test is still to be done. Results from customer tests have shown that the sensor works well even at air pressures well over 2 Bar above ambient.

3.5 Fridge Temperature Test

see Appendix 3 for Response Profile

 

Sensor 1

Sensor 2

Sensor 3

Sensor 4

Sensor 5

Output at -4 / % O2

19.88

19.79

19.84

19.68

19.82

Minimum Output / % O2

19.24

19.19

19.31

18.84

19.11

Output at 20 Deg C / % O2

20.90

20.90

20.90

20.90

20.90

The above data indicates that one sensor, number 4, would cause an instrument to alarm with a 19% O2 alarm. This does not take into account the fact that there would usually be some form of temperature compensation fitted into the instrument software.

3.6 Cross-sensitivity to Hydrogen

 

Sensor 1

Sensor 2

Sensor 3

Sensor 4

Sensor 5

Output in Air / mV

354.68

351.93

345.88

340.67

319.79

Output in 1% H2 Balance Air

336.55

331.51

325.75

320.14

303.72

 

 

 

 

 

 

Output in mv/%O2

16.97

16.83

16.54

16.30

15.30

Output in mv/%O2

16.26

16.02

15.74

15.47

14.67

1% H2 results in a % O2 depression of

-0.70

-0.82

-0.81

-0.83

-0.62

% Signal Depression

-3.37%

-3.91%

-3.86%

-3.96%

-2.98%

See appendix 4

3.7/ 3.8 Instrument Aspirator & Pump Tests

.

This test departed from the test method in that 8 sensors were tested for the effect of switching on a pump instead of the single sensor as specified in the test plan. In addition the simulated instrument was replaced by an 8-way flow hood and the 1L/min pump by one which produces a flow of 10l/min into the flowhood. A competitor sensor was tested as a reference sensor. The results show that the pressure induced by the pump switching on was not enough to make a simulated instrument go into alarm either when the pump was switched on or off. The maximum change was <0.2% Oxygen. This performance is a result of the pressure/bulk flow disc fitted above the capillary. This type of performance would also be seen if the pressure was changed using an aspirator.

see Appendix 5

3.9 Calibration Curve (Linearity) & Repeatability

3.9.1 Calibration Curve

See Appendix 6 For Graphs

Table of Linearity Response

Applied O2 concentration

Sensor 1

Sensor 2

Sensor 3

Sensor 4

Sensor 5

20.90

20.90

20.90

20.90

20.90

20.90

17.42

16.76

16.74

16.76

16.75

16.77

13.93

13.22

13.21

13.22

13.23

13.24

10.45

9.84

9.83

9.83

9.85

9.84

6.97

6.54

6.57

6.60

6.59

6.55

3.48

3.42

3.43

3.43

3.43

3.39

0.00

0.00

0.00

0.00

0.00

0.00

The sensor response to Oxygen is non-linear (as are all capillary based sensors). The response is actually logarithmic where the signal is proportional to the loge of the reciprocal of the volume fraction of O2.The slope is ~0.89 with an R2 figure approaching 100%. The performance standard calls for a maximum deviation of 2.5% of the quoted measuring range, which in the case of the EC410 sensor would amount to a range of 30% Oxygen and an error of 0.75% O2. The maximum error for the sensor appears to be at 13.93% O2 of 0.72% O2.

3.9.2 Repeatability

EC410 Repeatability

Sensor 1

Sensor 2

Sensor 3

Sensor 4

Sensor 5

Air 1

20.90

20.90

20.90

20.90

20.90

Air 2

20.88

20.87

20.84

20.90

20.92

Air 3

20.87

20.89

20.89

20.94

20.94

Air 4

20.91

20.90

20.90

20.90

20.89

Air 5

20.88

20.86

20.84

20.90

20.92

Air 6

20.89

20.87

20.84

20.90

20.93

Air 7

20.89

20.89

20.87

20.94

20.95

Air 8

20.88

20.89

20.85

20.93

20.95

Air 9

20.86

20.86

20.86

20.91

20.92

Air 10

20.86

20.83

20.81

20.89

20.92

s.d.

0.016

0.022

0.029

0.019

0.019

The repeatability is within ( 0.1% Oxygen. This is within the performance standard specification . See Appendix 7

3.10 Flow Rate. This test is yet to be completed

3.11 Warm up time

See initial stabilisation data, Section 3.1 and Appendix 1. Even if the sensor is not kept at the –600 mV potential it will take less than 90 to stabilise its output. It therefore meets the 5-minute time specification in section 5.4.15 of BSEN50104 for the output to be within (0.2% O2 or ( 2.5% of the measuring range

3.12 Response Time

See Appendix 8 for response profile. The t90 times are well within the t90 specification of 45 seconds and in most cases the measured t90 time is actually within the t20 specification of 10 seconds.

Final Output

t90 Output Down

t90 Down

t90 Output Up

t90 Up

327.1

47.9

6

296.0

8

323.3

47.8

8

292.4

12

329.5

50.5

6

298.5

8

314.1

50.7

8

284.8

10

323.4

46.5

6

292.6

10

3.13 Vibration

see Appendices 9 & 10 for graphs of output during the vibration tests in 3 axes. In no case did the sensor output of the sensor change by >more than (0.2% O2 or ( 2.5% of the measuring range.

3.14 Drop Test

BSEn50104 section 5.4.14 allows a maximum permanent change of 2.5% of the measuring range i.e. 2.5% x 30% O2 which is 0.75% O2. In addition it is desirable that the sensor output does not change enough to set of a latchable instrument alarm, which are usually set at 19.0% (Low) and 23% (High). The results showed little changes in the output compared to the significant changes seen with the lead –based sensors. See Appendix 11

3.15 Orientation

No measurable differences were seen, as the sensors were orientated around the axes. see statement in Appendix 12

3.16 Temperature

The specification in 5.4.7 of BSEn50104 is (5% of measuring range (i.e. 5%of 30% O2 which = (1.5%O2) or (0.5% O2 over the range 20 to –10 Deg C and up to 40 Deg C. This equates to 0.24% per degree C. The test data in Appendix 13 shows that the EC410 sensor output changes by ~0.3% per degree C.

In addition the EC410 sensor zero changes from 0 at 20 Degrees to between 0.7 –1.2% O2 at 40 Degrees C. This is within the (1.5%O2 maximum change allowed for in the performance specification. However it would seem that some form of temperature compensation in the instrument would be useful.

3.17 Pressure Coefficient Low Pressure

The sensor shows very good response to pressure change see Appendix 14. The actual change in percentage signal per mBar is, ~0.07compared to a competitor specification of 0.2%. Section 5.4.8 of BSEN 50104 calls for a maximum change of 0.65% Oxygen for 200 mBar change which is 0.325% change per mBar.

The sensors show a transient peak output (as do all Capillary sensors when the pressure is changed. See Appendix 14. This tends to increase as the pressure change increases up to a maximum four-fold change. This peak decays off rapidly reaching 10% of its stable value between 25 & 35 seconds.

3.18 Humidity

The results of the test at 40 Deg C (see table below and appendix 15) show a maximum deviation from 50% rh of 0.51 % O2 for sensor 1 at 90% rh. The other sensors showed <0.44% O2 change. This deviation is less than the 2.5% of the measuring range as stated in BSEB50104

Humidity

Sensor W0055

Sensor W0084

Sensor W0020

Sensor W0048

Sensor W0082

10.11

20.90

20.90

20.89

20.88

20.88

30.06

20.77

20.77

20.77

20.81

20.80

49.99

20.62

20.62

20.63

20.65

20.63

70.00

20.45

20.47

20.48

20.49

20.49

89.96

20.11

20.29

20.31

20.28

20.30

3.19 Air Velocity / Flow

This test is still to be done

3.20 Poisons

This test is still to be done this test is still to be done.

3.21 Physical Properties

3.21.1 Dimensions The sensor is approximately cylindrical in shape with a diameter of 20mm and a height of 16 mm.

3.21.2 The sensor weight is ~5.75 gms

3.21.3 The sensor pin layout is the same as that of a CTL 4 series toxic sensor

3.22 Effect of Carbon diOxide (1% Balance Air)

See Appendix 16

The sensors showed a drop in the Oxygen signal of 0.1/0.2 % consistent with the actual decrease in the Oxygen level by dilution with CO2. The CTL type sensor did not show a rise in Output, caused by absorption of CO2 into the alkali electrolyte. This test needs to be repeated in higher concentrations of CO2. In theory the acid electrolyte should be much less susceptible to effects produced by CO2 absorption. In particular the long-term performance of the EC410 sensor in backgrounds of CO2 would be better than that of the lead-based/alkali electrolyte sensor.

3.23 Long Term Test

This test is on-going see Appendix 17 for Performance graph. Some data was lost due to an equipment failure.

4.0 Conclusions

Test Reference

En 50104 Compliant

Fit for Purpose

Comment

Stabilisation

Initial stabilisation

Air Output

Passed

N2 Output

Passed

High Pressure change

Passed

‘Fridge’ Test

Passed

Hydrogen Cross-Sens.

Passed

Aspirator Test

Passed

Pump test is OK

Pump Test

Passed

Cal Curve/Repeatability

Passed

As capillary

Flow Rate

Untested

Warm up time

Passed

If Potential constant

Response time

Passed

Vibration

Passed

Drop Test

Passed

Orientation

Passed

Temperature

Temp co may be

needed

Low Pressure change

Passed

Humidity

Passed

Air flow/Velocity

Untested

Poisons

UnTested

Physical Properties

Passed

4 Series package

Effect of Carbon Di Oxide

Passed

More testing needed

Long Term Test

On Test

Results look good

Appendix 1 Stabilisation Graphs

APPENDIX 2 Oxygen Sensor Typical Response Profile to

Nitrogen

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

123012501270129013101330135013701390

Time /secs

Output mV

Air

N2

Applied

Air Applied

Appendix 2 Output in Air & Nitrogen

Appendix 3 'Fridge Test' Graph of EC410

Sensor Output when removed from

-4Deg C to Room Conditions

290

300

310

320

330

340

350

360

050010001500200025003000

Time /secs

Output / mv Negative

-4 Deg C

Room Temp

Sensor Removed from

'Fridge'

Appendix 4 EC410 Oxygen Sensor

Graph of Response to 1% Hydrogen

300

310

320

330

340

350

360

01020304050

Time/ secs

Output / mv Negative

1% H2

Appendix 3 Fridge Temperature Test

Appendix 4 Cross-Sensitivity to Hydrogen Test

Appendix 5 EC410 O2 Sensor Pump Test 1

Minute Positive Presssure Flow Rate (10 L/min)

into Flowhood

20.7

20.75

20.8

20.85

20.9

20.95

21

21.05

21.1

21.15

060120180240300360420480540600660720

Time / secs

Output /%O2

Appendix 5 Pump Test Result

Appendix 6 EC410 Sensor Linearity Test Graph

of Sensor Output vs Applied O2 (Zero

Compensated)

0.0

5.0

10.0

15.0

20.0

25.0

0.05.010.015.020.025.0

Applied O2 /%

Sensor Response / %

O2

Appendix 6 Linearity Graph to % Oxygen

Appendix 10 EC410 Sensors Vibration Test- 1st

Horizontal Axis

20.1

20.3

20.5

20.7

20.9

21.1

21.3

21.5

06001200180024003000360042004800

Time /secs

Output /%O2

Appendix 7 Repeatability

Appendix 10 EC410 Oxygen Sensor Vibration

Test 2nd Horizontal Axis

20.1

20.3

20.5

20.7

20.9

21.1

21.3

21.5

060012001800240030003600

Time /secs

% O2

Appendix 8

Appendix 11 EC410 (Blue) & Lead Based Sensors (Red / Purple)

Graph of Sensor Output During Drop Tests from 1 Metre

0

5

10

15

20

25

30

35

40

80140200260320380440500560620680740800860920

Time/ secs

Output / %O2

Sensor 1

Sensor 2

Sensor 3

Sensor 4

32mm

Lead

Sensor

20 mm

Lead

Sensor

Drop 1Drop 2

Drop 3

Drop 4

Drop 5

Appendix 9 See Appendix 2

Appendix 13 EC410 Oxygen Sensor Graph of Nitrogen

Output versus Temperature

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

-30-20-100102030405060

Temp / Deg C

Output / % O2

Appendices 9 & 10 Vibration Graphs

Appendix 13 EC410 Sensor Graph of % Sensor Response

versus Ambient Temperature

80%

85%

90%

95%

100%

105%

110%

115%

-40-200204060

Temp/ Deg C

% Output

Appendix 14 EC410 Oxygen Sensor

Graph of % Oxygen vs Pressure

19

19.5

20

20.5

21

21.5

22

22.5

23

23.5

80090010001100120013001400

Pressure / mBar

%O2

Appendix 11 Drop Tests

Appendix 14 EC410 Oxygen Sensor

Graph of sensor peak response to 10kPa

Pressure Changes

0

200

400

600

800

1000

1200

1400

1600

1800

0500100015002000250030003500

Time /secs

Sensor Output /mV

Appendix 12 Orientation Tests

Tests on the sensors showed no change in the output, as the sensor was orientated

Appendix 13 Temperature Response Graphs

Appendix 15 EC410 O2 Sensor Graph of Output

vs Ambient humidity at 40 Deg C

20.2

20.3

20.4

20.5

20.6

20.7

20.8

20.9

21

020406080100

% rh

% O2

Appendix 16 EC410 Oxygen Sensor

Graph of Sensor Response to succesive flows of

Air,1% CO2/ Air, then Air

20

20.2

20.4

20.6

20.8

21

21.2

21.4

21.6

21.8

22

050100150200250

Time /mins

Output /%O2

Appendix 14 Low Pressure Response Graphs

Appendix 7 EC410 Oxygen Sensor Repeatability Test

Graph of Response to Air vs Exposure

(each 5 minutes /Air N2)

20.50

20.60

20.70

20.80

20.90

21.00

21.10

21.20

21.30

21.40

21.50

012345678910

Exposure

Response / mV

APPENDIX 8 Oxygen Sensor Typical Response Profile to

Nitrogen

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

123012501270129013101330135013701390

Time /secs

Output mV

Air

N2

Applied

Air Applied

Appendix 15 Humidity Response Graphs

Appendix 9 EC410 Oxygen Sensor Vibration Test

Vertical Axis

20.2

20.4

20.6

20.8

21

21.2

21.4

21.6

06001200180024003000360042004800

Time /secs

Output /% O2

Appendix 16 Effect of Carbon dioxide

APPENDIX 17 EC410 Sensor Graph of Sensor

Output vs Time

14

15

16

17

18

19

20

21

22

23

24

0100200300400500

Time / Days

Signal/ % O2

Loss of Data from

Datalogger

Appendix 17 Long Term Performance