2 measurement steps, Analyzer overview 3.6.2 measurement steps – Hach-Lange POLYMETRON 9240 Operator Manual User Manual
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Analyzer Overview
3.6.2 Measurement steps
The 9240 is designed as a multi channel analyzer, though it can be used as a single channel
analyzer. The measurement parameters are different depending on whether the analyzer is set
up as a single or multi channel analyzer.
If the analyzer is configured as a single channel unit, the following parameters are required:
•
The on-line measurement time defines the measurement time of the sample, and how often
the measurement values are stored in memory. Regardless of this value the alarms, analog
outputs and RS 485 serial communication output are updated regularly (see
). The recommended (and default) value is 10 minutes, which will ensure
3 months of data stored internally.
•
The smart rinse facility can be used for rinsing the measurement cell after a calibration, grab
sample or sensor reactivation. If used, a maximum rinse time must be entered.
If the analyzer is configured as a multi channel unit, the following parameters are required in
addition to the on-line measurement time and smart rinse facility described above, and are
applicable to all configured channels:
•
A cycle time (total measurement and rinse time, see
below), which must be greater
than the on-line measurement time. The longest cycle time of all channels needs to be
entered to allow an efficient rinsing time. This will guarantee the accuracy (0.1 ppb or 5%) for
all configurations.
•
The search stability parameter can reduce the rinsing time after a change of measurement
channel. Set to Yes to get only accurate measurements transmitted thanks to the “smart
rinsing” cycle which automatically adapts the sample flow rate and duration of the rinsing
step, or set to No for a preferred fixed rinse time (cycle time minus on-line measurement
time), though accuracy could be at risk.
After each change of measurement channel, the analyzer rinses the measurement cell before
measuring the sodium level outputs during the on-line measurement time period as indicated in
the following diagram.
Note:
The choice of the right timings is essential for accurate measurements.
Figure 8 Analyzer cycle time