Thermo Scientific 49iQ Instruction Manual page 101

Operation
Settings
high range is active, the range mode selection status output is at half of
full-scale.
When the high range is active, the concentration must drop to 85% of
the low O range for the low range to become active.
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In addition, each O range and analog output has a span coefficient so
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that each range can be calibrated separately. This is especially necessary
if the two ranges are not close to one another. For example, the low O
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range is set to 0–50 ppb and the high O range is set to 0–20,000 ppb.
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Thermo Scientific 49iQ Instruction Manual 3-73