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SEMI E69-0298 © SEMI 1998, 2003 3 Figure 2 Terminal-Based Linearity for Mass Flow Contr oller 5.2.20 reproducibility, short-term — the closeness of agreement among a num ber of measured values at a setpoint, under the sa…

SEMI E69-0298 © SEMI 1998, 2003 2

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

5 Terminology

5.1 Abbreviations and Acronyms

5.1.1 FS — Full scale

5.1.2 kPa — Kilopascal

5.1.3 MFC — Mass flow controller

5.1.4 NC — Normally closed

5.1.5 NO — Normally open

5.1.6 psia — Pounds per square inch absolute

5.1.7 sccm — Standard cubic centimeters per minute

5.1.8 slm — Standard liters per minute

5.2 Definitions

5.2.1 accuracy — the closeness of agreement between

an observed value and the true value; the total

uncertainty of an observed value, including both

precision and bias.

5.2.2 accuracy curve — the curve fitted through the

average measured values over the specified range of the

device under test (DUT).

5.2.3 accuracy, device — the total uncertainty over a

specified range of the device. Device accuracy over a

range is stated as the worst case accuracy taken over all

tested setpoints in this range.

5.2.4 bias — the difference, at a setpoint, between the

measured value and the sum of the setpoint value and

the zero offset. The measured values of a flow standard

include its total uncertainty.

5.2.5 cardinal setpoint — a specific setpoint to assess

the accuracy of the device under test. For this test

method, the cardinal setpoints are 10%, 50%, and 100%

of full scale.

5.2.6 deadband — the range through which a setpoint

may be varied, upon reversal of direction, without

initiating an observable change in output signal.

5.2.7 downscale reading — a reading approached from

a setpoint greater than the current setpoint and beyond

the deadband.

5.2.8 downscale value, average — the sum of all

downscale readings, in one cycle, at a single setpoint,

divided by the number of these values.

5.2.9 flow standard — a device used to measure the

actual mass flow through the DUT.

5.2.10 linearity — the closeness to which a curve

approximates a straight line. It is measured as a non-

linearity and expressed as a linearity.

5.2.11 linearity, terminal-based — the maximum

absolute value of the deviation of the accuracy curve

(average of upscale and downscale values) from a

straight line through the upper and lower setpoint limits

of the accuracy curve (see Figure 1).

5.2.12 measured value — the actual flow through a

device under test, expressed in sccm or slm, as

measured by a standard, preferably primary.

5.2.13 measured value, average — the sum of all

readings (both upscale and downscale) for all cycles, at

a single setpoint, divided by the number of these

readings.

5.2.14 operating conditions, normal — the range of

operating conditions within which a device is designed

to operate and for which operating influences are stated

[ISA S51.1].

5.2.15 operating conditions, reference — the range of

operating conditions of a device within which operating

influences are negligible [ISA S51.1].

5.2.16 operating influence — the change in a

performance characteristic caused by a change in a

specified operating condition from reference operating

conditions, all other conditions being held within the

limits of reference operating conditions [ISA S51.1].

5.2.17 precision — the closeness of agreement among

the measured values at a setpoint. It is often expressed

as a standard deviation.

5.2.18 repeatability — the closeness of agreement

among a number of measured values at a setpoint,

under the same operating conditions, operator,

apparatus, laboratory, and short intervals of time. It is

usually measured as a nonrepeatability and expressed as

a repeatability in percent of reading [ISA S51.1].

5.2.19 reproducibility — the closeness of agreement

among repeated measured values at a setpoint, within

the specified reference operating conditions, made over

a specified period of time, approached from both

directions. It is usually measured as a non-

reproducibility and expressed as a reproducibility in

percent of average reading. Reproducibility includes

hysteresis, deadband, long-term drift, and short-term

reproducibility [ISA S51.1].

NOTE 1: Between repeated measurements, the input may

vary over the range, and operating conditions may vary within

normal operating conditions.

SEMI E69-0298 © SEMI 1998, 2003 3

Figure 2

Terminal-Based Linearity for Mass Flow Controller

5.2.20 reproducibility, short-term — the closeness of

agreement among a number of measured values at a

setpoint, under the same operating conditions, operator,

apparatus, laboratory, and short intervals of time,

approached from both directions. The approach must be

from beyond the deadband. It is usually measured as a

nonreproducibility and expressed as a reproducibility in

percent of reading. Short-term reproducibility includes

repeatability, hysteresis, deadband, and shortterm drift.

5.2.21 setpoint — the input signal provided to achieve

a desired flow, reported as sccm, slm, or percent-full

scale.

5.2.22 setpoint limit, lower — the lowest setpoint at

which the instrument is specified to operate.

5.2.23 setpoint limit, upper — the highest setpoint at

which the instrument is specified to operate, usually full

scale.

5.2.24 span — the full-scale range of the DUT.

5.2.25 stability — the ability of a condition to exhibit

only natural, random variation in the absence of

unnatural, assignable-cause variation.

5.2.26 standard conditions — 101.32 kPa, 0.0°C (14.7

psia, 32°F)

5.2.27 uncertainty, total — the range within which the

true value of the measured quantity can be expected to

fit; an indication of the variability associated with a

measured value that takes into account the two major

components of error — bias and the random error

attributed to the imprecision of the measurement

process.

5.2.28 upscale reading — a reading approached from a

setpoint less than the current setpoint and beyond the

deadband.

5.2.29 upscale value, average — the sum of all upscale

readings, in one cycle, at a single setpoint, divided by

the number of these values.

5.2.30 zero drift — the undesired change in electrical

output, at a no-flow condition, over a specified time

period, reported in sccm or slm.

5.2.31 zero offset — the deviation from zero, at a no-

flow condition, reported in sccm or slm.

6 Summary of Test Method

6.1 Specific procedures are given for characterizing

MFCs discharging to atmospheric pressure or into a

vacuum using accepted reference standards to

determine reproducibility and zero drift (see Figure 2).

Figure 3

Test Flowchart