Operation
Range Menu
Thermo Electron Corporation Model 42i Low Source 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.
Auto Range Mode The auto range mode switches the NO, NO
2
and NO
x
analog outputs
between high and low ranges, depending on the NO
x
concentration level,
except when continuous NO mode is active. The high and low ranges are
defined in the Range menu.
For example, suppose the low ranges are set to 200 ppb and the high ranges
are set to 1000 ppb (Figure 3-6). Sample concentrations below 200 ppb are
presented to the low ranges analog outputs and sample concentrations
above 200 ppb are presented to the high ranges analog outputs. When the
low ranges are active, the status output is at 0 volts. When the high ranges
are active, the status output is at half of full-scale.
When the high ranges are active, the NO
x
concentration must drop to 95%
of the low NO
x
range for the low ranges to become active.
In addition to each channel having two ranges, each channel has two span
coefficients. 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, if the low NO range is set to 0–200 ppb and the high
NO range is set to 0–20,000 ppb.
Channel Pin Description
1 14 NO High Range
233 NO
2
High Range
315 NO
x
High Range
4 34 NO Low Range
517 NO
2
Low Range
636 NO
x
Low Range
Ground 16, 18, 19, 35, 37 Signal Ground
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