Iec 60746 1 2003

INTERNATIONAL STANDARD IEC 60746 1 Second edition 2003 01 Expression of performance of electrochemical analyzers – Part 1 General Expression des qualités de fonctionnement des analyseurs électrochimiq[.]

Specification of values and ranges

Manufacturers specifying the performance of complete analyzers, sensor units or electronic units, shall give statements covering all quantities considered to be applicable performance characteristics.

These statements shall cover the aspects which will be described in the following subclauses.

General

The reference value or range, along with the rated range of use for all influence quantities, must be clearly stated These values should be selected exclusively from one of the usage groups I, II, or III as defined in IEC 60359, ensuring compliance with the standard.

According to IEC 60654-1, usage groups provide standard values, and any deviations from these values must be clearly and explicitly stated by the manufacturer, highlighting them as exceptions.

Manufacturers should clearly specify if analyzers or electronic units are designed to operate under different rated ranges for environmental conditions compared to mains supply conditions, ensuring users understand the distinct operational parameters for each.

NOTE 2 When the sensor and electronic units are separate, the rated range for climatic conditions for the individual units may be different.

Electrochemical analyzers often use sensors designed to measure aqueous solutions, making it essential to adhere to the ambient temperature Class I standards of IEC 60359 This compliance helps prevent freezing within the sensor and sample lines, ensuring accurate and reliable measurements.

The rated ranges of use for an analyzer must be clearly specified based on sample conditions at the analyzer inlet for on-line analyzers or at the sensor unit for insertion sensor types These specifications should include key parameters such as flow rate (when applicable), pressure, temperature, and the maximum allowable rate of change for sample temperature to ensure accurate and reliable performance.

The operational limit conditions must be clearly defined to ensure that the analyzer maintains its functionality without any damage or performance degradation This applies when any performance characteristics or influence quantities fall within these specified limits during a given time period, or indefinitely if no time frame is specified.

NOTE Absence of degradation of performance means that, after re-establishing reference conditions or rated operating conditions, the analyzer again satisfies the requirements concerning its performance.

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU.

The storage and transport limit conditions must be clearly defined to ensure that the analyzer, while not in use, does not suffer permanent damage or performance degradation These conditions apply when any influence factors reach any value within the specified storage or transport parameters for a designated period, or indefinitely if no time frame is specified.

NOTE Absence of degradation of performance means that, after re-establishing reference conditions or rated operating conditions, the analyzer again satisfies the requirements concerning its performance.

5.2.5 Constructional materials in contact with the sample shall be stated.

The manufacturer must specify the parameter values necessary to ensure compatibility between any sensor unit and the electronic unit, unless the analyzer system is provided as a complete unit Additionally, clear instructions should be provided to restore accurate operation within the original performance specifications when replacing either the sensor or electronic unit.

Performance characteristics requiring statements of rated values

5.3.1 The manufacturer shall state minimum and maximum rated values for the property to be measured (range or ranges).

5.3.2 Minimum and maximum rated values for output signals corresponding to the rated values as given in 5.3.1.

Signals must be expressed in units of voltage, current, or pressure, with specific load requirements clearly indicated For voltage signals, the minimum allowable load in ohms should be specified, while for current signals, the maximum allowable load in ohms must be stated Additionally, any impact of capacitive or inductive loads on the output signal should be clearly detailed to ensure accurate performance and compatibility.

Where the analyzer or electronic unit has multiple outputs, the statements above should be made for all outputs.

If the output signal is an electrical current, see also IEC 60381-1; if it is pneumatic, see also

Uncertainty limits to be stated for each specified range

These should be in accordance with 6.4.2 in IEC 60359 Wherever appropriate, statements shall be made of the uncertainty limits near the lower and upper ends of each analyzer range.

5.4.1 Limits of intrinsic uncertainty shall be stated for use under reference conditions in a manner which allows them to be inferred over the rated range.

“The greatest of ±x % of range or ± y % of true value”

“ ± 1 display digit ± y % of true value”

5.4.2 For an analyzer or electronic unit, the linearity uncertainty shall be stated separately.

Where a non-linear output is provided, the manufacturer shall accurately state the relationship between the output value and the measured parameter.

NOTE Deviation from linearity is strictly considered as an uncertainty only if a linear output is claimed For analyzers having non-linear outputs, the term “conformity” may be used.

1 For example: "sensor model XXX for use with electronics unit YYY".

2 For example: "when replacing the sensor unit, recalibrate the analyzer using calibration solutions ", or "when replacing the electronics unit, enter the following parameters as data …".

The manufacturer must specify any sample components known to cause interference effects in the intended application, detailing whether these effects are positive or negative and their magnitude The selection of interfering components, their concentration levels, and test methods can be mutually agreed upon by the manufacturer and the user, except when specific requirements are outlined in other parts of the IEC 60746 series.

5.4.4 The manufacturer shall state the repeatability and the basis on which it was calculated.

The manufacturer must specify the drift for at least one time interval selected from the list in section 6.2.5, ensuring that the chosen interval is relevant to the intended application.

(see note of 6.2.5) The warm-up time is always excluded from the time interval.

Other performance characteristics

Although no statements of uncertainty limits are required for the performance characteristics listed below, the manufacturer shall state their values or ranges for each specified measuring range.

5.5.3 Delay and 90 % response times for both upscale and downscale changes.

5.5.5 The quantitative effect on indicated value of the property to be measured produced by variation of the sample temperature.

This note highlights that the specified maximum variation for the influence quantity is reached at the limits of the sample temperature, which may be included as part of the statement of the rated operating conditions.

The quantitative effects on the indicated value of the property being measured, caused by changes in other influencing factors, may be unknown However, if there is reason to believe that simple coefficients exist, these should be specified for variables such as sample flow rate, sample pressure, and ambient temperature.

Note that these conditions may be included within the statement of the rated operating parameters, indicating that at the boundaries of the influencing factors, the specified maximum allowable variations have been attained.

To ensure the accuracy of rated values provided by manufacturers, standardized test procedures are essential, allowing for consistent comparison of different analyzers used in similar applications These procedures help users verify that an analyzer meets their performance requirements in a fair manner, using methods comparable to those employed by the manufacturer This clause outlines general test methods to assess various performance characteristics, while subsequent parts of the IEC 60746 series offer more specific procedures tailored to particular analyzer types In special cases where standard tests are unsuitable, customized test procedures can be mutually agreed upon by the manufacturer and user.

General

6.1.1 Tests shall be performed with the analyzer (including accessories) ready for use after warm-up time and after performing all necessary adjustments according to the manufacturer’s instructions.

Unless otherwise specified, all influencing factors must be maintained at reference conditions during the relevant tests, and throughout testing, the analyzer should be operated at its rated voltage and frequency to ensure accurate and consistent results.

The sensor must be maintained in optimal condition as specified by the manufacturer, ensuring that flow conditions and other critical factors such as sample flow rate, pressure, and temperature comply with the manufacturer's guidelines for accurate performance.

6.1.4 When measuring the intrinsic uncertainty, the combination of values and/or ranges of influence quantities shall remain within the reference conditions which include relevant tolerances on reference values.

When measuring the variation of a performance characteristic caused by an influence quantity, all other factors must remain within their reference conditions The property value being measured and the range of the influence quantity can take any value within their specified operating ranges.

During testing, external adjustments may be repeated at intervals specified by the manufacturer or at any appropriate interval, provided that such adjustments do not affect the uncertainty being evaluated.

Adjustments must be carried out when uncertainty values are specified to be valid only after such adjustments Measurements should be taken immediately following the adjustment to prevent any drift from affecting the results.

In principle, measurement uncertainties from test instruments should be negligible compared to the uncertainties being evaluated It is important to follow local standards that define quality assurance procedures, as well as the guidelines outlined in section 6.1.8.

6.1.8 When the uncertainty of any test instrument is not negligible, the following rule should apply:

When testing an analyzer against a reference instrument with a known uncertainty \$n\$, and the determined uncertainty is \$n_1\$, the actual uncertainty \$e\$ of the analyzer is calculated as \$e = n_1 - n\$ If another party later checks the analyzer's performance using a test instrument with known uncertainty \$m\$ and finds the determined uncertainty to be \$m_1\$, it can only be validly claimed that the analyzer is underperforming if the difference \$m_1 - m\$ exceeds the previously established uncertainty \$e\$.

The above discussion presents a basic approach to uncertainty, focusing solely on instrument systematic uncertainty For a thorough and rigorous analysis of claimed uncertainties and deviations from specified performance, a strict statistical evaluation is essential This process would likely involve calculating t or F test statistics and consulting statistical tables to verify the significance of the claims.

6.1.9 Test equipment shall include all of the necessary test solutions (see 3.5, 3.6)

Test equipment must include suitable simulators for testing electronic units when these units are provided separately from sensor units In such cases, the requirements outlined in sections 6.1.7 and 6.1.8 apply to the simulators Specifications for these simulators differ depending on the type of analyzer and can be found in other parts of the IEC 60746 series that address specific analyzers.

Sensor units supplied separately must be tested with appropriate calibration or test solutions, as specified in sections 3.5 and 3.6 This testing should be conducted using a suitable electronic unit, which can be the analyzer's own unit if it has undergone prior testing.

Test procedures

Intrinsic uncertainty

To ensure accurate measurement, record the output reading of the unit in the specified property units with all influence quantities at their reference values Apply values near the upper and lower limits of the measuring range, as well as at least one additional point within the range Perform this procedure a minimum of six times to calculate the mean intrinsic uncertainty at the three selected points, enhancing the reliability of the measurement results.

Linearity uncertainty

At least five measurements should be taken, evenly distributed across the measurement range, with two measurements near the range limits A straight line must then be fitted to these readings using the least squares method to ensure accurate data analysis.

The maximum deviation between the recorded values and this straight line is the linearity uncertainty It is expressed in terms of the units of the property to be measured.

When the output signal is a non-linear function of the measured parameter, it is essential to apply the manufacturer's linear transform function to the signal before conducting data analysis This ensures accurate interpretation of the data The deviation from the fitted line, as previously defined, represents the "independent conformity," which is a key metric in assessing measurement accuracy.

Repeatability

The results obtained as in 6.2.1 shall be used to calculate the repeatability at each applied value as the standard deviation of the indications at that level.

Output fluctuation

An applied value near the mid-scale of the measuring range should be maintained for at least five minutes or ten times the 90% response time if longer During this period, the maximum peak-to-peak deviation, whether random or regular, from the mean output must be determined to ensure accurate measurement stability.

When an electronic unit or analyzer features variable time constants in its output circuit, the output fluctuation must be measured using the same time constant specified for delay and 90% response times to ensure accurate and consistent results.

For the purposes of this standard, any spikes that can be definitively attributed to external electromagnetic fields or supply mains transients are classified as changes in influence quantities and can be excluded from the assessment of output fluctuation.

Drift

The test procedure is designed to evaluate the drift characteristics under specified reference conditions, ensuring assessment over at least one time interval and at a minimum of one point within the measuring range.

If only one point is used, a value near the 50 % span should be used as the test point.

The analyzer must be fully warmed up and calibrated following the manufacturer's instructions before use It should be operated continuously and strictly according to these guidelines throughout the test Importantly, no external adjustments to the analyzer are permitted once the test has begun.

The appropriate input should be continuously applied to the analyzer, if feasible, until a stable indication is achieved This process must occur at the beginning, end, and at least six evenly spaced time intervals throughout the test period to ensure accurate and reliable results.

The time interval for which the stability limits are determined should be chosen appropriately for the specific application from the following values:

The results will be analyzed using linear regression over time, with the slope of the regression line for each input value representing the drift This drift will be reported, for example, as x pH units per month, providing a clear measure of change over time.

Short-term drift in measurements is typically assessed over periods of up to 24 hours, while long-term drift for online analyzers is evaluated over extended durations ranging from 7 days to 3 months Understanding both short-term and long-term drift is essential for accurate and reliable analyzer performance.

Delay (T 10) and 90 % ( T 90) response times

Signals indicating the minimum and maximum values of the measuring range must be applied consecutively until stable readings are achieved on a recording device, such as a chart recorder or data logger, which precisely records the corresponding time intervals.

The delay times (T₁₀) for both increasing and decreasing step changes, as well as the 90% response times (T₉₀) for these changes, can be accurately determined from the data record, as illustrated in Figure 1.

Warm-up time

The electronic unit must be powered off and allowed to cool to ambient temperature, typically overnight Once cooled, a stable signal ranging from 75% to 95% of the span should be applied Afterward, the analyzer is switched on, and the reading is recorded to ensure accurate measurement.

Recording shall be continued until the response has reached and remained within the specified intrinsic uncertainty band (taking account of repeatability) for a period of 15 min.

The warm-up time is the interval from the time the electronic unit was switched on until the beginning of this 15 min period.

Variations

Variations arise from uncertainties caused by changes in influence quantities, with the most common and relevant factors detailed in sections 6.2.9 and 6.2.10 However, not all sources of uncertainty apply to every application The process for assessing the impact of each influence quantity follows a similar procedure.

Uncertainties must be assessed at two points near the lower and upper ends of the measuring range, although a single point may suffice if the influence quantity is an event, such as an electrical transient or drop The process begins with all parts of the analyzer set to reference conditions, then measuring the variation in indication caused by adjusting the influence quantity to the lower limit of its rated range After returning to reference conditions, the variation caused by changing the influence quantity to the upper limit is determined, followed by another return to reference conditions.

Analyzers can incorporate automatic or manual compensation for some physical parameters.

Compensation accounts for both the sensor properties and the measured parameter within the working fluid, referencing a standard value of the influencing quantity.

When compensation functions are manually adjusted or disabled, it is essential to record both the compensated and uncompensated values This practice ensures accurate assessment of the compensation function's correct operation, enhancing reliability and performance.

Interference uncertainty must be assessed for components that impact the sensor and are likely present in the sample, with measurements taken at two points near the lower and upper limits of the measuring range This variation can only be accurately determined for the entire analyzer or sensor unit, rather than the electronics unit alone.

Generally a test solution is applied first without, then with the interfering substance present.

The interfering component must be introduced at the highest expected concentration and at approximately half that level Each test should be conducted in triplicate, with the mean variation for each parameter value reported as the interference uncertainty This approach ensures accurate assessment of interference effects across different concentration levels.

Primary influence quantities

These influence quantities are normally important, and shall be tested whenever relevant:

– radio frequency interference (see local standards);

Other influence quantities

These should also be specified and tested where relevant Test procedures can be found in

IEC 60068, IEC 60770 and IEC 61298 The following list is not exhaustive.

3 For example, pH sensors are normally corrected for the Nernstian temperature response of the sensor.

A correction for properties of the solution to a reference temperature, often 25 °C, may also be applied as a slope in terms of pH/°C.

4 This may be chosen with consideration to an application, or simply to establish the rated operating range for that component.

Recommended standard values of influence – Quantities affecting performance from IEC 60359

The rated ranges of use of the influence quantities below have been divided into the following three usage groups:

I: for indoor use under conditions which are normally found in laboratories and factories and where apparatus will be handled carefully.

II: for use in environments having protection from full extremes of environment and under conditions of handling between those of Groups I and III.

III: for outdoor use and in areas where the analyzer may be subjected to rough handling.

Influence quantities typically impact electronic units directly and are specifically relevant to them, while sensor units, immersed in the sample, are mainly affected by the sample conditions In in situ analyzers, where both sensor and electronic units are immersed in the sample, the sample conditions influence the electronic units as well, rather than the usual influence quantities.

The effects of the external environment on the sensor unit may need to be stated separately.

– Reference value (to be chosen from): 20 °C, 23 °C, 25 °C or 27 °C.

– Limit range for storage and transport: -40 °C to +70 °C.

NOTE Many sensors need protection from freezing conditions.

A.1.2 Relative humidity of the air

Manufacturers often specify time limits for applying extreme temperature and humidity conditions separately, as these extremes rarely occur simultaneously They should also clearly define any limitations on the continuous operation under combined temperature and humidity conditions to ensure optimal performance and reliability.

– Reference range at 20 °C, 23 °C, 25 °C or 27 °C: 45 % to 75 %.

Usage group I: 20 % to 80 % excluding condensation;

Usage group II: 10 % to 90 % including condensation;

Usage group III: 5 % to 95 % including condensation.

– Reference value: existing local barometric pressure.

Usage group I: 70,0 kPa to 106,0 kPa (up to 2 200 m);

Usage groups II and III: 53,3 kPa to 106,0 kPa, (up to 4 300 m)

– Limit range of operation: equal to the rated range of use unless otherwise stated by the manufacturer.

– Limit range for storage and transport: to be stated by the manufacturer.

A.1.4 Heating effect due to solar radiation

– Reference value: no direct irradiation.

Usage groups I and II: no direct irradiation;

For usage group III, the combined impact of solar radiation and ambient temperature must not cause the surface temperature to surpass the level reached at an ambient temperature of 70 °C alone This ensures safe and reliable operation under specified environmental conditions.

A.1.5 Velocity of the ambient air

Usage groups I and II: 0 m/s to 0,5 m/s;

– Limit range of operation: equal to the rated range of use unless otherwise stated by manufacturer.

A.1.6 Sand and dust contents of the air

– Reference value: no measurable contents.

Usage groups I and II: negligible contents (i.e will have negligible effect on the analyzer);

Usage group III: to be stated by the manufacturer.

– Limit range of operation: equal to the rated range of use unless otherwise stated by manufacturer.

– Limit range for storage and transport: to be stated by manufacturer.

A.1.7 Salt contents of the air

Usage groups I and II: negligible contents;

Usage group III: to be stated by the manufacturer.

– Limit range of operation: to be stated by the manufacturer.

– Limit range of storage and transport: to be stated by the manufacturer.

A.1.8 Contaminating gas or vapour contents of the air

– Rated ranges of use: usage groups I to III: to be stated by the manufacturer.

A.1.9 Liquid water contents of the air

Usage group II: drip water;

Usage group III: splash water.

– Reference value: position as stated by the manufacturer.

Usage groups I and II: reference position ±30°;

Usage group III: reference position ±90°.

Please note that the specified rated usage ranges apply exclusively to electronic units without orientation-sensitive indicators For electronic units equipped with built-in orientation-sensitive indicators, manufacturers must provide appropriate guidance and statements to ensure proper use.

– Reference value: ventilation not obstructed.

Usage groups I and II: negligibly obstructed;

Usage group III requires that any obstruction of ventilation combined with ambient temperature must not cause the surface temperature to exceed the level observed at an ambient temperature of 70 °C with unobstructed ventilation.

– Reference value: no measurable value.

Usage groups II and III: to be stated by the manufacturer.

A.3.1 Mains supply voltage (considering a distorted waveform) d.c and a.c (r.m.s.) a.c (peak)

– Reference value: Rated value Rated value

Usage group II: –12 % to +10 % –17 % to +15 %

Usage group III: –20 % to +15 % –30 % to +25 %

The distortion is determined by a factor, β, in such a way that the waveform is inside an envelope formed by:

Y 2 = (1 - β) A sin ωt – Reference value β = 0 (sine-wave).

Usage groups II to III: β = 0,10.

The values of β are valid when the analyzer is connected to the supply mains.

NOTE 1 The above formulae may be applied over the half cycle or a full cycle depending on whether the zero crossings are equally spaced or not.

NOTE 2 If the a.c peak voltage exceeds the values stated in A.3.1, the mains supply under consideration cannot be used.

– Reference value 0 % of supply voltage

Usage group I: 0,5 % of supply voltage

Usage group II: 1,0 % of supply voltage

Usage group III: 5,0 % of supply voltage

– Limit range of operation: 5,0 % of supply voltage

The values given are peak to peak values of the ripple voltage expressed as a percentage of the average d.c supply voltage.

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Tiêu đề	Expression of Performance of Electrochemical Analyzers – Part 1: General
Trường học	International Electrotechnical Commission
Chuyên ngành	Electrochemical Analyzers
Thể loại	Standards document
Năm xuất bản	2003
Thành phố	Geneva

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