4230 Flow Meter
Section 1 Introduction
1-4
bridge, proportional to the increase of air pressure, caused in
turn by an increase in level of the flow stream. This bridge is fed
from a constant-voltage source; changes in output are the result
of changes in pressure.
1.3.3 Automatic Drift
Compensation Valve
The 4230 Flow Meter contains the software and circuitry nec-
essary to measure the output of the pressure transducer at zero
pressure. When the flow meter is first turned on, and periodically
after that, the processor actuates the automatic drift compen-
sation valve, which connects the input port of the pressure trans-
ducer to the reference port. With the two ports connected, it then
measures the output offset. The flow meter stores this offset
reading in memory and uses it in level calculations. The flow
meter periodically repeats this zero-offset measurement and
stores the new reading in memory. The repetition of this process
causes zero drift in the pressure transducer or the amplifier to
cancel out, eliminating the most significant cause of drift, espe-
cially when the flow meter is operating at low water levels.
The valve also provides temperature compensation at zero
pressure. The software controlling the 4230 determines how
often this compensation cycle is repeated. Drift compensation
cycles range from two to fifteen minutes.
1.4 Software Upgrades To update the software in a 4200 Series Flow Meter, you do not
have to return the unit to the factory or replace an EPROM. With
Flash Memory, software updates can easily be installed in the
field with a disk, a computer, and a cable. See Section 5 for
instructions for Flash software updates. For more information
about installing software upgrades in the 4230 Flow Meter,
contact your Isco representative or call the factory.
1.5 Controls, Indicators,
and Connectors
The controls, indicators, and connectors of the 4230 Flow Meter
are listed in Table 1-1, and their functions are briefly described.
Refer to Figure 1-2 for a view of the controls, indicators, and con-
nectors.
1.6 Technical
Specifications
The technical specifications for the 4230 Flow Meter are found in
Table 1-2. The anticipated longevity for a roll of paper used in the
printer is shown for various chart speeds in Table 1-4. Battery
life expectancy for three programming combinations is found in
Table 1-5, with a brief description of how to make battery calcu-
lations immediately following.
Note
Various options and accessories used with the 4230 are
described throughout the manual. For convenience, the Isco
part numbers for these items are listed on the Accessory Parts
List found at the end of the Replacement Parts List. Part num-
bers for equipment not listed on this sheet are available from
the factory.
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