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SEMI F56-0600 © SEMI 2000 2 8 Apparatu s 8.1 T he equipment and instrument a t io n required to com plet e this t est m eth od are s hown in Fig ur e 2. 8.2 D C Power Supply , to provide t he required voltage to the MFC …
SEMI F56-0600 © SEMI 20001
SEMI F56-0600
TEST METHOD FOR DETERMINING STEADY-STATE SUPPLY
VOLTAGE EFFECTS FOR MASS FLOW CONTROLLERS
This test method was technically approved by the Global Facilities Committee and is the direct responsibility
of the North American Facilities Committee. Current edition approved by the North American Regional
Standards Committee on April 10, 2000. Initially available on www.semi.org May 2000; to be published
June 2000.
1 Purpose
1.1 The purpose of this document is to define a
method for characterizing mass flow controllers
(MFCs) being considered for installation into a high-
purity gas distribution system. This method will
quantify the steady-state supply voltage effects on the
MFC's ability to accurately deliver set point flow
values.
2 Scope
2.1 This procedure applies to thermal mass flow
controllers. It is intended to measure the delivered
mass flow rate variation as a function of deviation from
the reference steady-state supply voltage. The test
method is designed for DC-powered MFCs. The
supply voltage effects include voltage depression and
over-voltage variations in the DC supply.
2.2 This standard does not purport to address safety
issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish
appropriate safety and health practices and determine
the applicability of regulatory limitations prior to use.
3 Limitations
3.1 This test method is not designed for AC-powered
MFCs. This test method addresses steady-state effects
and does not address any effects caused by transient
power supply behavior.
4 Referenced Standards
4.1 None.
5 Terminology
5.1 Acronyms and Abbreviations
5.1.1 DUT — device under test
5.1.2 MFC — mass flow controller
5.1.3 NIST — National Institute of Standards and
Technology
5.1.4 psia — pounds per square inch absolute
5.1.5 psig — pounds per square inch gauge
5.2 Definitions
5.2.1 actual flow — flow value measured by the flow
standard.
5.2.2 indicated flow — flow value derived from the
MFC.
5.2.3 Reference voltage(s) — manufacturer's recom-
mended power supply voltage(s).
5.2.4 stable — the state a signal level obtains when its
magnitude varies by less than or equal to ±2.0% of full
scale over a one-minute period.
6 Summary of Method
6.1 This test method consists of varying the steady-
state supply voltage to an MFC in ±1% (of rated
supply) increments from the reference voltage span.
Both the positive and negative supply voltages will be
varied independently and together in 1% increments.
The MFC flow output is monitored at 0% and 100% of
its operating range (see Table 1). At each incremental
change as well as at the reference supply voltage, the
MFC flow and flow standard outputs are recorded at
0% and 100% of its operating range. The test shall end
when a ±3% of full-scale output flow change is noted
between the flow at the reference voltage and at an
incremental change point. A flow chart outlines the
procedure (see Figure 1).
7 Interference’s
7.1 Because of fluctuations in ambient temperature or
a changing load on the power supply, the reference
steady-state supply voltages may change. These
changes in supply voltages may adversely effect the
MFC's ability to deliver setpoint flow. The magnitude
of this effect can be measured by this test method.
7.2 The user of an MFC can use the data generated by
this method to evaluate the impact of steady-state
supply voltage variations on the MFC's ability to
deliver setpoint flow values. Knowing the magnitude
of this effect and the power level variations, allows the
user to decide on what measures to take to reduce this
effect, if necessary.
SEMI F56-0600 © SEMI 2000 2
8 Apparatus
8.1 The equipment and instrumentation required to
complete this test method are shown in Figure 2.
8.2 DC Power Supply, to provide the required voltage
to the MFC under test, with the capability to vary its
output over the range of ±30 VDC at 500 mA, and with
ripple less than 0.1% rms.
8.3 DC Power Supply Monitor/Recorder, placed in
parallel with the DC power supply, and capable of
measuring the DC voltage to within ±5 mV over the
entire operating range of the supply.
8.4 Flow Output Monitor, connected to the MFC
output and signal common/ground points. The
monitor/recorder shall be capable of measuring over a
range of 0–10 VDC to within ±5 mV.
8.5 Flow Standard, installed downstream and in series
with the flow through the MFC. The flow standard
shall be capable of measuring flow changes within
±0.3% of full scale.
8.6 Current Meter, connected in series in the power
common line of the DC power supply, capable of
measuring over a range of 0–200 mA to within ±1 mA.
9 Reagents and Materials
9.1 Test Gas, nitrogen
10 Safety Precautions
10.1 The user must know the respective
instrumentation, practice proper handling of test
components, and understand good laboratory practices.
10.2 The user should not exceed the ratings (such as
pressure, temperature, flow, and voltage) of the
components.
11 Preparation of Apparatus
11.1 Setup and Schematic — See Figures 2 and 3.
11.2 The test gas source and delivery system must be
capable of satisfying the test volume flow rate at a
constant pressure, +0.1 psia.
11.3 The test gas source and delivery system must be
capable of delivering a gas at ambient temperature
±2°C for the duration of each analysis. The ambient
temperature shall be held to 22 ±1°C.
12 Calibration and Standardization
12.1 All instrumentation shall be calibrated with NIST
traceable standards and shall be under current
calibration.
13 Procedure
13.1 Install the MFC into the test setup per
manufacturer's recommendations.
13.2 Apply power to all devices sho wn in Figure 2 per
manufacturer's specifications. Allow the devices to
warm up for the duration specified by the equipment
manufacturer.
13.3 Set the DC power supply to the manufacturers
recommended reference voltage. Verify the voltage
magnitude using the power supply monitor.
13.4 Purge the system with nitrogen for a length of
time equal to ten times the amount of time it takes to
replace the system volume with the test MFC at its full-
scale rated flow rate.
13.5 Close the inlet shut-off valve and then the outlet
shut-off valve located adjacent to the MFC (see Figure
3). Adjust the MFC setpoint to zero flow. Follow the
manufacturer's recommendations for adjusting the MFC
zero. If the MFC has an auto-zero function, leave it
active and note this fact on the data sheet in Table 1.
Wait for the signals to become stable. Record on the
data sheet (see Table 1) three separate readings of the
MFC flow output, the power supply voltages, and the
current of the power supply common.
13.6 Vary the positive DC power supply voltage in
+1% steps from the reference value while holding the
negative supply at its reference value.
NOTE 1: If reference voltage is +15 V, the first step is a
change in voltage of +0.15 V.
13.7 After the monitored signals become stable, record
the MFC zero value, the current value, and the power
supply voltage magnitudes. Record the measurements
at each step-change of power level on the data sheet.
Continue to increase the positive supply voltage span
until the MFC zero point changes by ±3% of full scale
flow, the MFC zero output point remains unstable for
five minutes, or the voltage level changes to +115% of
original value.
13.8 Return the power supply level to the original
reference value and repeat Section 13.5.
13.9 Repeat the procedure described in Section 13.6,
with the following exception: Decrease the power
supply span in 1% decrements until either the MFC
zero changes by ±3% of full scale, the zero output point
remains unstable for five minutes, or 85% of the
original value is reached.
13.10 Return the power supply level to the original
reference value, repeat Section 13.5, and go to Section
13.10.
SEMI F56-0600 © SEMI 20003
13.11 Repeat Sections 13.6 through 13.9, with the
following exception: Vary the negative DC power
supply while holding the positive power supply at its
reference value.
13.12 Vary both DC power supply voltages together in
+1% steps from the reference value.
NOTE 2: If the reference voltages are ±15 V (30 V span), the
first step is a change in voltage of +0.15 V increasing the span
to +15.15 V (30.3 V span).
13.13 After the monitored signals become stable,
record the MFC zero value, the current value, and the
power supply voltage magnitudes. Record the
measurements at each step change of power level on the
data sheet. Continue to increase the supply voltage
span until the MFC zero point changes by ±3% of full
scale flow, the MFC zero output point remains unstable
for five minutes, or the voltage level changes to +115%
of original value.
13.14 Return the power supply level to the original
reference value, repeat Section 13.5, and go to Section
13.13.
13.15 Repeat Section 13.11, with the following
exception: Decrement the power supply voltages by 1%
and go to Section 13.14.
13.16 Return the power supply level to the original
reference value, repeat Section 13.5, and go to Section
13.15.
13.17 Open the inlet and outlet shut-off valves that are
adjacent to the MFC (see Figure 3) and adjust the MFC
set point to 100%. Insure that all reference conditions
are within the specified tolerances. Once the output
signals become stable, record the MFC output signal,
the power supply voltage, the flow standard output, and
the current value.
13.18 Vary the positive DC power supply voltage in
+1% increments from the reference while holding the
negative power supply at its reference value as
described in Section 12.6. Record, on the data sheet, the
measurements of MFC flow output, power supply
voltage, flow standard output, and current meter signal
after the values become stable. Continue to increase the
voltage in 1% increments until the MFC or flow
standard signal changes by ± 3% of full scale, or the
MFC output signal remains unstable for five minutes,
or the voltage level changes to +115% of original value.
13.19 Return the power supply level to the original
reference value, repeat Section 13.5, and go to Section
13.18.
13.20 Open the inlet and outlet shut-off valves that are
adjacent to the MFC and adjust the MFC setpoint to
100%. Repeat the procedure described in Section
12.16, but decrease the positive supply voltage in 1%
decrements until either the flow signal changes by ±3%
of full scale, the MFC output signal remains unstable
for five minutes, or 85% of the original value is
reached.
13.21 Return the power supply level to the original
reference value, repeat Section 13.5, and go to Section
13.20.
13.22 Repeat Sections 13.15 through 13.19, with the
following exception: Vary the negative DC supply
voltage level while holding the positive power supply at
its reference value and go to Section 13.21.
13.23 Repeat Section 13.15 and then go to Section
13.22.
13.24 Vary both DC power supply voltages together in
+1% steps from the reference value.
NOTE 3: If the reference voltages are ± 15 V (30 V span),
then the first step is a change in voltage of +0.15 V increasing
the span to +15.15 V.
13.25 After the monitored signals become stable,
record the MFC flow and flow standard values, the
current value, and the power supply voltage
magnitudes. Record three measurements at each step-
change of power level on the data sheet. Continue to
increase the supply voltage span until either the flow
changes by ± 3% of full scale flow, the MFC zero
output point remains unstable for five minutes, or the
power level has been changed to +110% of span (±16.5
V).
13.26 Return the power supply level to the original
reference value, repeat Section 13.5, and go to Section
13.24.
13.27 Open the inlet and outlet shut-off valves that are
adjacent to the MFC and adjust the MFC setpoint to
100%. Repeat the procedure described in Section
13.22, with the following exception: Decrease the
supply voltages together in 1% decrements until either
the flow signal changes by ± 3% of full scale, the MFC
output signal remains unstable for five minutes, or until
the supply voltage span has changed ± 15% (± 12.75
V). Then go to Section 13.25.
13.28 Return the power supply level to the original
reference value, repeat Section 13.5, and go to Section
14.
14 Calculations or Interpretation of Results
14.1 Convert the MFC indicated flow output data and
the flow standard output data to percent of full scale
flow as follows: