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7.1 THEORY OF OPERATION (pH).
This section is a
general description of how the Model 1054B pH oper-
ates. This section is for those users who desire a
greater understanding of the analyzer's operation.
The measurement of the process’ pH is accom-
plished by the use of two electrodes within the sen-
sor. The glass electrode is pH sensitive and
generates a high impedance millivolt potential directly
proportional to the process pH. The reference elec-
trode is a second half cell that completes the circuit
via a liquid junction. The high impedance signal is
preamplified at the sensor to allow a stable noise-free
signal that can be transmitted up to 1,000 feet.
The Model 1054B pH also measures the process tem-
perature via a platinum 100 ohm RTD imbedded in
the sensor. Advanced circuitry is used to eliminate
errors due to changes in cable resistance. The ana-
lyzer uses this temperature measurement to compen-
sate for changes in the sensor millivolt output caused
by temperature change.
7.2 THEORY OF OPERATION (ORP).
This section is
a general description of how the 1054B ORP oper-
ates. The selected sensor generates a voltage
dependent on the oxidation reduction potential (ORP)
measured in the process. This voltage signal is fed
into a high-impedance amplifier (preamp) prior to
transmission to the Model 1054A ORP. The high
impedance and low voltage of the sensor make a pre-
amplifier necessary for a reliable ORP signal to reach
the transmitter.
The analog signal from the preamp is digitized by the
signal conditioning circuit, becoming a digital signal
(proportional to the ORP) that can be read by the
CPU. This digital signal is then used to calculate an
ORP value.
The CPU also contains an on board electrically erasa-
ble and programmable read-only memor y
(EEPROM) which maintains memory during power
outages. The CPU is supported by read-only memory
(ROM) containing the operating instructions for the
CPU.
The CPU controls the operation of the liquid crystal
display, Alarm 1, Alarm 2 and also creates a pulse
width modulated (PWM) signal. The PWM signal is
converted by the isolated output circuit (located on
the power board) to a selectable current output (0 to
20mA or 4 to 20mA).
The keyboard is a matrix of on/off switch positions
that the CPU scans periodically to determine if a
button is depressed. The CPU reacts when a key is
depressed to display a different parameter or to mod-
ify its function in some manner. Even though the ORP
measurement is not temperature sensitive, process
temperature is accurately measured at the ORP sen-
sor through the use of a PT-100 RTD and is displayed
by the 1054A ORP over the range of -15 to135°C. For
a more accurate temperature reading the analyzer
temperature indication may be standardized to the
process temperature by pressing the
TEMP
key and
adjusting the indicated value.
MODEL 1054B pH/ORP
SECTION 7.0
THEORY OF OPERATION
SECTION 7.0
THEORY OF OPERATION
Содержание 1054B
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Страница 11: ...6 MODEL 1054B pH ORP SECTION 2 0 INSTALLATION FIGURE 2 2 Panel Mounting Tab Installation DWG NO REV 41054A26 A ...
Страница 15: ...10 MODEL 1054B pH ORP SECTION 2 0 INSTALLATION FIGURE 2 6 Electrical Wiring DWG NO REV 41054B03 C ...
Страница 16: ...11 MODEL 1054B pH ORP SECTION 2 0 INSTALLATION FIGURE 2 7 Integral Preamp Wiring DWG NO REV 41054B32 B ...
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