Honeywell AQ3STF Sulfur Dioxide Gas so2 Sensor Mode d'emploi

Marque: Honeywell

Modèle: AQ3STF Sulfur Dioxide Gas so2 Sensor

Taper: Mode d'emploi

CONTENTS

Document Purpose

The Gas Response Curve

Linearity

Temperature Characteristics

Variation of Sensitivity with Temperature

Variation of SO2 Reading with Temperature after Compensation

Variation of Baseline Offset with Temperature after Compensation

Long-term Sensitivity Drift

Repeatability

Calibration Guidelines

Recommended Gas Flow Rates

Recommended Circuit

Compensation Logics of AQ3 Series Sensors

Cross Sensitivity Table

CHARACTERIZATION

NOTE

AQ3STF Sulfur Dioxide Gas Sensor

DOCUMENT PURPOSE

The purpose of this document is

to provide indicative, technical

performance data for the AQ3STF

gas sensor to assist in the

integration of the sensor into gas

detection instrumentation. The

sensor has been subjected to a

testing program as part of the

development process. Within this

document, detailed information

on the results of this program is

presented. All data has been taken

from equipment using a +5 Vdc

power supply.

This document and the information

contained within does not

constitute a speciﬁcation. The

data is provided for informational

purposes only and is not warranted

by the manufacturer. It should be

used in conjunction with the AQ3

Product Datasheet, Operating

Principles(OP20) and the Product

Safety Datasheet (PSDS 19).

, NOTICE

• Ensure the sensor is powered on for a minimum of 24 hours before use.

• Sensor may experience higher failure risk when continuously exposed to

90 %RH/50ºC for > 168 hours.

• All baseline tests are performed under clean dry air instead of ambient air.

AQ3STF Sulfur Dioxide Gas Sensor Characterization Note | sps.honeywell.com/ast | 

AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

THE GAS RESPONSE CURVE

The data in Figure 1 shows a typical

response curve for the AQ3STF.

Test data was taken from current

production at the time of release of

this document, and reﬂects the typical

performance of a production batch at

this time.

The data in Figures 2 and 3 shows typical

response and recovery proﬁles based on

the data above.

Figure 1. AQ3STF Gas Response and Recovery Proﬁle

Figure 2. AQ3STF Gas Response Proﬁle

Figure 3. AQ3STF Gas Recovery Proﬁle

100

200

300

400

500

050100 15

Concentration(ppb)

Time (s)

AQ3STF: EOL Test

Applied Concentration (ppb)

100

200

300

400

500

02040608

Concentration (ppb)

Time (s)

AQ3STF: Response Curve

T90: 5s

(Typical Value < 40 s)

100

200

300

400

500

02040608

Concentration (ppb)

Time (s)

AQ3STF: Recovery Curve

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AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

LINEARITY

The data in Figure 4 shows the typical

linearity performance of the AQ3STF gas

sensor when subjected to differing Sulfur

Dioxide concentrations which is

0 ppb to 1000 ppb.

The presented results reﬂect the

performance of a typical production

batch. Across typical measurement

ranges for atmospheric monitoring, the

sensor can often be considered linear.

Figure 4. Output Linearity from 0 ppb to 1000 ppb

100

200

300

400

500

600

700

800

900

1000

0100 200300 400500 600700 800900 1000

Measured Concentration (ppb)

Applied Concentration (ppb)

AQ3STF: Linearity

Applied Concentration (ppb) 0 20 40 80 100 200 400 500 800 1000

Measured concentration (ppb) 0 18 39 79 99 201 400 499 799 1000

TEMPERATURE

CHARACTERISTICS

Variation of Sensitivity with

Temperature

The sensitivity of the AQ3STF Series gas

sensor will vary as a function of ambient

temperature. The data in Figure 5 shows

the typical output performance across

the operating temperature range and is

presented normalized to the 20°C value

with clean air.

For instruments that are expected to

function across a wide range of ambient

temperatures. Honeywell recommends

that an electronic compensation

algorithm is used to ensure maximum

accuracy. The presented results reﬂect

the performance.

Figure 5. Sensitivity vs. Temperature without Compensation

Temperature (°C) 20 10 0 10 20 30 40 50

+3SD (equivalent to 99.7% conﬁdence) 90 94 97 100 100 107 108 113

+2SD (equivalent to 95% conﬁdence) 88 92 96 99 100 106 106 109

Mean (%) 82 88 93 96 100 102 102 101

2SD (equivalent to 95% conﬁdence) 76 84 90 94 100 99 99 92

3SD (equivalent to 99.7% conﬁdence) 74 83 88 93 100 97 97 88

100

120

140

-20 -10 01020304050

Sensitivity normalized at 20°C (%)

Temperature (°C)

AQ3STF: Sensitivity vs Temperature

+3SD

+2SD

Mean

-2SD

-3SD

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AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

Variation of SO2 reading with

Temperature after Compensation

To ensure maximum accuracy, an

electronic compensation algorithm is

being used for above result.

The Data in Figure 6 shows the AQ3STF

reading performance across the

operating temperature range after

compensation.

Figure 6. SO2 Reading vs Temperature after Compensation

-38%

-28%

-18%

-8%

13%

23%

33%

250

300

350

400

450

500

550

-20 -10 01020304050

SO2 Reading Variation

SO2 Reading After Compensation (ppb)

Temperature (°C)

AQ3STF: Reading Aer Compensaon

+3SD

+2SD

Mean (ppb)

-2SD

-3SD

Temperature (°C) 20 10 0 10 20 30 40 50

+3SD (equivalent to 99.7% conﬁdence) 449 427 424 418 411 425 434 450

+2SD (equivalent to 95% conﬁdence) 429 417 415 410 407 417 424 433

Mean (%) 387 397 398 393 399 401 403 399

2SD (equivalent to 95% conﬁdence) 346 376 382 377 391 385 382 365

3SD (equivalent to 99.7% conﬁdence) 325 366 373 368 387 377 372 348

Baseline Offset with Temperature

after Compensation

The electrical output in the absence of

target gas

(baseline offset) of the AQ3STF will

vary as a function of the ambient

temperature . The data on the right shows

typical AQ3STF performance across

the operating temperature range, for

sensors calibrated at 20°C with clean air.

Although the variation is relatively small,

Honeywell recommends the use of offset

correction factors so as to minimize

inaccuracies in the span measurement.

The presented results are being

compensated with correction factors.

You may ﬁnd the correction factors in the

note on page 9. The presented results

reﬂect the typical performance of a

production batch.

Figure 7. Baseline vs Temperature after Compensation

-80

-60

-40

-20

-30 -20 -10 0102030405

Reading after compensation(ppb)

Temperature (°C)

AQ3STF: Baseline Reading@T

AQ3STF Sulfur Dioxide Gas Sensor Characterization Note | sps.honeywell.com/ast | 

AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

LONGTERM SENSITIVITY

DRIFT

The typical long term sensitivity of the

AQ3STF is represented in Figure 8, which

reﬂects the performance of a typical

production batch The sensor batches

under test were stored and tested in

ambient conditions.

Figure 8. LongTerm Sensitivity Drift

REPEATABILITY

The data in Figure 9 show the

repeatability performance of the AQ3STF

sensor when exposed repeatedly to

SO2. The presented results reﬂect the

performance of a typical production

batch.

Figure 9. Repeatability of AQ3STF Sensor response to 400 ppb SO2

-30%

-20%

-10%

10%

20%

30%

0306090120 150 180 210

Sensitivity drift (%)

Time (day)

AQ3STF: Long-term Stability Performance

-50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600700 800 900 1000 1100

Response (ppb SO2)

Time (s)

AQ3STF: Repeatability when Exposed to 400 ppb SO2

1st

application

2nd 3rd 4th 5th 6th

Mean response (ppb) 412 408 406 405 404 402

Standard deviation (ppb) 4 3 5 6 5 4

AQ3STF Sulfur Dioxide Gas Sensor Characterization Note | sps.honeywell.com/ast | 

AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

CALIBRATION GUIDELINES

Honeywell AQ3 Series gas sensors provide very stable signals over time and for

many applications, instruments containing AQ3 gas sensors only require periodic

recalibration. The time interval required between initial calibration and subsequent

recalibrations is dependent on various factors. In strenuous applications involving

extremes of operation, or for sensors used in safety applications, frequent instrument

calibration may be required. Electrochemical gas sensors need a certain amount of

oxygen to function. Generally, a few thousand ppm oxygen is sufﬁcient. However, as

calibration normally involves exposing the sensing face of the AQ3 gas sensor to gas

for a relative short period of time, a calibration gas need not contain oxygen-sufﬁcient

oxygen is supplied from the ambient air, for a limited time. In most cases, a ﬁve minute

exposure time is sufﬁcient to achieve a stable calibration signal.

Safety Note: Many AQ3 gas sensors are designed to be used in safety critical

applications. To ensure that the sensor and/or instrument in which it is used, is

operating properly, it is a requirement that the function of the device is conﬁrmed by

exposure to target gas (bump check) before each use of the sensor and/or instrument.

Failure to carry out such tests may jeopardize the safety of people and property.

Please be aware the recommended ﬂow rate below is for a batch (6 sensor).

Sensor Warm-up

time

Calibration Gas

Concentration Gas Path Saturation EOL Step

AQ3CO 24 hours 1 ppm CO 1 ppm 2 L/min for 10 minutes Ambient Air 1 min à Clean Air 3 mins à

1 ppm CO 3 mins à Clean Air 2 mins

AQ3STF 24 hours 400 ppb SO25 ppm 2 L/min for 5 minutes Ambient Air 2 mins à Clean Air 3 mins à

400 ppb SO2 2 mins à Clean Air 3 mins

AQ3OZ 24 hours 400 ppb O32 ppm 2 L/min for 40 minutes Ambient Air 1 min à Clean Air 40 mins à

400 ppb O3 5 mins à Clean Air 3 mins

AQ3ND 24 hours 400 ppb NO25 ppm 100 mL/min for 30 minutes Ambient Air 1 min à Clean Air 40 mins à

400 ppb NO2 5 mins à Clean Air 5 mins

Figure 10. Calibration Schematic

AQ3STF Sulfur Dioxide Gas Sensor Characterization Note | sps.honeywell.com/ast | 

AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

RECOMMENDED GAS FLOW

RATES

A suitable ﬂow rate is required to ensure

accurate calibration – it also means that

the response from an AQ3 gas sensor is

equivalent in conﬁgurations where gas is

ﬂowing over the sensor and those where

the sample is allowed to diffuse into the

sensor. The minimum ﬂow rate which

is required will be different depending

on the gas sensor type – these are

shown in the table Please be aware the

recommended ﬂow rate is for a single

sensor.

Gas Sensor Type Flow Rate (ml/min)

Carbon Monoxide, CO AQ3CO 500

Nitrogen Dioxide, NO2AQ3ND 500

Ozone, O3AQ3OZ 500

Sulfur Dioxide, SO2AQ3STF 500

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AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

RECOMMENDED CIRCUIT

The recommended circuit for un-biased 4-electrode AQ3 Series gas sensor is shown

below. The description below can be applied to all AQ3 Sensors (unless otherwise

noted). The circuit is essentially divided into two parts. The ﬁrst part is a potentiostat

circuit designed to keep the sensor sensing -reference voltage constant. An op amp is

used to compare voltage at the reference pin to a stable bias voltage. Any movement

of the reference pin voltage is compensated for by adjusting voltage on the counter

pin. The circuit should draw no current from the sensor reference pin or the sensor

output will be unstable. Further, the offset voltage of this op amp needs to be very

low (typically 60 uV to 100 uV) or be nulled out, as offset in the circuit will appear

as baseline offset in the sensor / instrument. The second part of the circuit, applied

to both sensing and auxiliary pins, is a trans-impedance ampliﬁer (TIA). The job of

this circuit is to amplify the small current generated at the sensing pin when gas is

detected and convert to a much larger voltage output which can be easily measured

by instrumentation. Input is via a small load resistor (R106, R121 in the example

circuit), whose value is speciﬁed on the sensor datasheet. Gain of this circuit is

controlled by the feedback resistor, which is typically 20k to 1M (R107, R122 in the

example). The circuit gain should be high enough to give a readable output, but not

so high as to saturate the op amp at its highest (overload) output. The circuit below

is based on operation from a single rail 5 V op-amp circuit with rail to rail output and

a virtual ground reference for the sensor of 2.5 V. The output from the circuit will be

positive with respect to virtual ground for sensors measuring oxidizing gases (CO and

SO2) while the op amp output voltage ranges from 2.5 V to 4.5 V (2 V margin). Output

will be negative with respect to virtual ground for sensors measuring reducing gases

(NO2 and O3) while the op amp voltage ranges from 2.5 V to 0 V (2.5 V margin). Please

be aware that signals for NO2 and O3 sensors are negative when using below circuit,

remember to reverse the output signal when you use this circuit in real applications.

U100 – This LDO (LP5907 or similar,

with low noise and low IQ) is to provide a

stable voltage for the circuit. Please refer

to chosen LDO datasheet for more detail.

U104 – This ampliﬁer act as a trans-im-

pedance ampliﬁer (TIA) - current to

voltage converter only.

U102 – This dual op amp ampliﬁer

should have either a low offset (<100 uV

typical) or have its offset nulled out. This

ampliﬁer should also have a low power

consumption. A suitable op amp is the

OPA2336E or similar. This ampliﬁer is

used both as potentiostat and a current

to voltage converter (trans-impedance

ampliﬁer).

U101 – The Zener diode circuit is to

provide an accurate and stable reference

voltage (2.5 V) to serve as virtual ground.

, NOTE

Other op amp conﬁgurations may be used, including single- and dual-supply rails. In this case the reference voltage (bias

voltage) will need to change to suit the circuit output range and sensor output, avoiding saturation of the op amp at limits of

operation and ensuring a stable bias/virtual ground reference voltage.

Figure 11. Recommended Circuitry for 4-electrode AQ3 Series Gas Sensors

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AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

COMPENSATION LOGICS OF AQ3 SERIES SENSORS

This compensation logics provides customers with insights into our air-quality AQ3

Series sensors.

AQ3 Series sensors, including AQ3CO, AQ3STF, AQ3ND and AQ3OZ, are specially

designed for high-precision and high-accuracy detection of ppb-level CO, SO2,

NO2 and O3 in ambient environment. As electrochemical sensors, AQ3 Series are

sensitive to the temperature variation, resulting in zero-background current change

and sensitivity change that are well-known for long years. Compensation for these

changes is indispensable for real-time and high-accuracy monitoring of ppb-level air

pollutants. Therefore, in this Characterization Note we are mainly focusing on well-

simulated algorithms to make up for these changes, thus enhancing the accuracy and

precision of result in the ﬁeld application.

There are four electrodes in AQ3 Series sensors, i.e. sensing electrode, auxiliary

electrode, reference electrode and counter electrode. For customers, the signals of

sensing electrode and auxiliary electrode are most useful to compensate for zero-

background current and sensitivity in practical application. Based on our experiment

results, we provide the best-ﬁt compensation algorithms for different kinds of AQ3

Series sensors. Some key parameters are explained as below:

WE real-time signal of sensing electrode, nA

WET

signal of sensing electrode at speciﬁc temperature in highly pure and

dry air, nA

WE20 signal of sensing electrode at 20°C in highly pure and dry air, nA

AE real-time signal of auxiliary electrode, nA

AE20 signal of auxiliary electrode at 20°C in highly pure and dry air, nA

STsensitivity of sensing electrode at speciﬁc temperature, nA/ppm

S20 sensitivity of sensing electrode at 20°C, nA/ppm

CF cross-factor, different sensors have different CF, no unit

RNO2 AQ3ND concentration reading, ppb

RO3 AQ3OZ concentration reading, ppb

r1 a function of temperature, usually r1=a1*T2+b1*T+c1, T/°C

r2 a function of temperature, usually r2=a2*T2+b2*T+c2, T/°C

r3 a function of temperature, usually r3=a3*T2+b3*T+c3, T/°C

The table below lists the compensation formula for different sensors, and the table

above gives the parameters for different sensors.

Sensor

Type Compensation Formula

AQ3STF Concentration (ppb) = [(WEWE20) - r1*(AEAE20)-r2

CF1*RNO2*r3*S20CF2*RO3*r3*S20] /(r3*S20) *1000

AQ3OZ Concentration (ppb) = [(WEWE20-r2CF1*RNO2*r3*S20)/(r3*S20)]*1000

AQ3CO Concentration (ppb) = (WEWE20– r2)/(r3*S20)*1000

AQ3ND

Note:

r1 and r2 compensates for the

zero-background current change

due to temperature variation

r3 compensates for the sensitivity

change due to temperature variation;

r1, r2 and r3 are usually function

of temperature /°C

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AQ3STF Sulfur Dioxide (SO2) Gas Characterization Note

CROSS SENSITIVITY TABLE

Whilst AQ3 Series gas sensors are designed to be highly speciﬁc to the gas they are

intended to measure, they will still respond to some degree to various other gases. The

table below is not exclusive and other gases not included in the table may still cause a

sensor to react.

IMPORTANT NOTE: The cross sensitivity data shown below does not form part

of the product speciﬁcation and is supplied for guidance only. Values quoted

are based on tests conducted on a small number of sensors and any batch may

show signiﬁcant variation. For the most accurate measurements, an instrument

should be calibrated using the gas under investigation.

Gas Gas Concentration Cross Interference

Carbon Monoxide, CO 5 ppm ~None

Nitric Oxide, NO 5 ppm ~None

Nitrogen Dioxide, NO20.4 ppm 110%<x%<0%

Hydrogen Sulﬁde, H2S 5 ppm ~None

Ozone, O3 0.4 ppm 50%<x%<0%

Isobutylene, C4H85 ppm ~None

FOR MORE INFORMATION

Honeywell Advanced Sensing

Technologies services its customers

through a worldwide network of sales

ofﬁces and distributors. For application

assistance, current speciﬁcations, pricing

or the nearest Authorized Distributor,

visit our website or call:

USA/Canada +1 302 613 4491

Latin America +1 305 805 8188

Europe +44 1344 238258

Japan +81 (0) 367307152

Singapore +65 6355 2828

Greater China +86 4006396841

Honeywell

Advanced Sensing Technologies

830 East Arapaho Road

Richardson, TX 75081

sps.honeywell.com/ast AQ3STF Characterization Note ECN 5062 | 0027281EN | 1 | 05/21

WARRANTY/REMEDY

Honeywell warrants goods of its manufacture

as being free of defective materials and

faulty workmanship during the applicable

warranty period. Honeywell’s standard product

warranty applies unless agreed to otherwise by

Honeywell in writing; please refer to your order

acknowledgment or consult your local sales

ofﬁce for speciﬁc warranty details. If warranted

goods are returned to Honeywell during the

period of coverage, Honeywell will repair or

replace, at its option, without charge those

items that Honeywell, in its sole discretion,

ﬁnds defective. The foregoing is buyer’s sole

remedy and is in lieu of all other warranties,

expressed or implied, including those of

merchantability and ﬁtness for a particular

purpose. In no event shall Honeywell be

liable for consequential, special, or indirect

damages.

While Honeywell may provide application

assistance personally, through our literature

and the Honeywell web site, it is buyer’s sole

responsibility to determine the suitability of

the product in the application.

Speciﬁcations may change without notice.

The information we supply is believed to

be accurate and reliable as of this writing.

However, Honeywell assumes no responsibility

for its use.

m WARNING

MISUSE OF

DOCUMENTATION

• The information presented in

this characterization note is for

reference only. Do not use this

document as a product installation

guide.

• Complete installation, operation,

and maintenance information

is provided in the instructions

supplied with each product.

Failure to comply with these

instructions could result in death or

serious injury.

Honeywell AQ3STF Sulfur Dioxide Gas so2 Sensor Mode d'emploi

Marque: Honeywell

Modèle: AQ3STF Sulfur Dioxide Gas so2 Sensor

Taper: Mode d'emploi

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