Thermo Scientific 450iQ Instruction Manual page 102

range is active, the range mode selection status output is at 0 volts.
When the 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 95% of
the low SO range for the low range to become active.
2
In addition, each SO range and analog output has a span coefficient so
2
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
SO range is set to 0–50 ppb and the high SO range is set to 0–10000
2 2
ppb.
450iQ Instruction Manual Thermo Scientific