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Settings and Calibration Model 7500ZA
Teledyne Analytical Instruments 74
6.8.2 Span Calibration
The Model 7500ZA requires periodic span calibration at or near the
full scale value on the range of interest. It requires a prepared standard
gas containing a known concentration of the measured
species. For span calibration gas on the NOX, SO
2
, CO
2
,
CO and CH
4
channels, TAI recommends using a gas source
containing 90-100% of the measured species in a
background known to be compatible with the instrument.
For the oxygen channel, with units that include a built-in
O
2
sensor, use a prepared standard gas with an O
2
concentration
of 90 to 100% full scale on the anticipated measuring range.
If the instrument is fitted with an external zirconia
sensor, use a prepared standard of 1-2% O
2
.
To perform a span calibration:
1. Press the SPAN key on the Measurement screen to
display the Manual Span Calibration screen.
2. Select the channel (component) to be calibrated
using the UP or DOWN key and then press ENT.
Calibration gas will then flow to the sensor.
Note: For the Ch (components) in which “both” is set
in the calibration range setting (Refer to Section
6.2.3), span calibration is performed on both
ranges.
3. Wait until the indication is stable. After the
indication has stabilized, press ENT. Span
calibration on the selected range will be performed.
Note: On channels for which “AR” (auto ranging) is
enabled (See Section “6.1.1) the cursor
automatically moves to the range that is
enabled. See Section 6.2.4 “Setting of auto
calibration component/range”. Calibration is
then carried out on that range.
To close the Span Calibration screen or to abort the
entry midway, press the ESC key. The previous screen will
return