Operation
Range Menu
Thermo Electron Corporation Model 48i Instruction Manual 3-11
Table 3-3. Default Analog Outputs in Dual Range Mode
Note All channels are user definable. If any customization has been made to
the analog output configuration, the default selections may not apply.
Autorange Mode The autorange mode switches the CO analog outputs between a high and
low ranges, depending on the concentration level. The high and low ranges
are defined in the Range menu.
For example, suppose the low range is set to 50 ppm and the high range is
set to 100 ppm (Figure 3-6). Sample concentrations below 50 ppm are
presented to the low ranges analog outputs and sample concentrations
above 50 ppm are presented to the high ranges analog outputs. When the
low range is active, the status output is at 0 volts. When the high range is
active, the status output is at half of full-scale.
When the high range is active, the concentration must drop to 95% of the
low CO range for the low range to become active.
In addition, each CO analog output has a span coefficient. There are two
span coefficients so that each range can be calibrated separately. This is
necessary if the two ranges are not close to one another. For example, the
low CO range is set to 0–50 ppm and the high CO range is set to 0–10,000
ppm.
Channel Pin Description
1 14 CO High Range
2 33 CO Low Range
3 15 None
4 34 None
5 17 None
6 26 None
Ground 16, 18, 19, 35, 37 Signal Ground
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