Model 400E Ozone Analyzer
Instruction Manual
EPA Protocol Calibration
P/N 04316 Rev: B
193
For each midpoint:
ZERO CAL M
RANGE = 500.0 PPB
O3 =XXX.X
< TST TST >
ZERO
SPAN
CONC
EXIT
WAIT 10
MINUTES
Or until the
reading
stabilizes and
the
SPAN
button
is displayed
SAMPLE RANGE = 500.0 PPB O3 =XXX.X
< TST TST > CAL
CALZ
CALS
SETUP
Record the O
3
reading as
displayed on the
instrument’s front
panel
Press
EXIT
to
Return to the
Main
SAMPLE
Display
ACTION:
Allow Calibration Gas diluted to
proper concentration for Midpoint N
ACTION:
Allow Calibration Gas diluted to
proper concentration for
Midpoint N+1
Plot the analyzer responses versus the corresponding calculated concentrations to
obtain the calibration relationships. Determine the straight line of best fit
(y = mx + b) determined by the method of least squares (e.g., see Appendix J of
Volume I of the Q.A. Handbook
6
).
After the best-fit line has been drawn, determine whether the analyzer response is
linear. To be considered linear, no calibration point should differ from the best-fit
line by more than 2% of full scale.
8.4.
Dynamic Multipoint Calibration Check
The EPA-prescribed calibration procedure is based on photometric assays of O
3
concentrations in a dynamic flow system. It is based on the same principles that
the M400E uses to measure ozone. The theory is covered in Section 10 of this
manual.
Since the accuracy of the calibration standards obtained by this calibration
procedure depends entirely on the accuracy of the photometer, it is very important
that the photometer is operating properly and accurately. The fact that the
photometer makes a ratio measurement (I/I
o
) rather than an absolute
measurement eases this task.