Output Communication; Electronics - Thermo Scientific 146i Instruction Manual

System Description

Electronics

Monitoring Signals
Measurement
Calculations

Output Communication

Electronics
8-8 Model 146i Instruction Manual
The instrument includes a sample solenoid valve and a reference solenoid
valve. The instrument can be configured to measure O
(standard cycle) or every four seconds (fast cycle). Every cycle, the two
solenoid valves switch the sample gas and reference gas streams between the
two cells. One cell contains sample gas, the other cell contains reference gas
and vice versa.
During a standard cycle, the cells are purged for seven seconds and
measurements are taken for three seconds. During a fast cycle, the cells are
purged for three seconds and measurements are taken for one second.
During every cycle, the instrument calculates the natural logarithm of the
sample gas frequency to reference gas frequency ratio in each cell and
averages these results to optimize instrument accuracy. These logarithms
provide the basis for calculating the ozone concentrations. The logarithms
are stored in a rolling stack of 30 logarithms which are averaged by the
instrument's averaging time function.
The background values for O
span and are subtracted from the ozone calculated to yield a corrected value.
The front panel display, serial and Ethernet data ports, and analog outputs
are used to communicate the results of the measurement calculations. The
front panel displays the O
seconds (standard cycle) or every four seconds (fast cycle).
The analog output ranges are user selectable via software. The analog
outputs are defaulted based on the measurement range. The defaults are
calculated by dividing the data values by the full-scale range for each of the
three parameters and then multiplying each result by the user-selected
output range. Negative concentrations can be represented as long as they are
within -5% of full-scale. The zero and span values may be set by the user to
any desired value.
All electronics operate from a universal switching supply, which is capable of
auto-sensing the input voltage and working over the entire operating range.
Internal pumps and heaters all operate on 110VAC. An optional
transformer is required if operating on the 210-250VAC or 90-110VAC
ranges.
An on/off switch controls all power to the instrument, and is accessible on
the front panel.
are corrected for temperature, pressure, and
3
concentration. The display is updated every ten
3
every ten seconds
3
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