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Instruction Manual
IM-106-340AC-1, Rev. 1.0
April 2005
1-5
SPS 4001B
THEORY OF
OPERATION
The Oxymitter 4000 is one of the few instruments found in industry that permit
the permanent piping of a calibration standard into the probe. Most
instruments measuring pressure, flow, or temperature, require that a
calibration standard be brought to the instrument or that the instrument be
taken to the calibration source in the instrument shop.
The permanent calibration gas connections allow for autocalibrations to occur
without operator intervention. The following paragraphs describe how an
Oxymitter 4000 is autocalibrated when used with the SPS 4001B.
In addition to the calibration methods available via the Oxymitter 4000
keypad, HART communicator, AMS software, or a remote contact, the SPS
4001B works in conjunction with the Oxymitter 4000's CAL RECOMMENDED
feature to perform an autocalibration.
This feature automatically performs an impedance check every hour on the
Oxymitter 4000. If a calibration is recommended and its contact output signal
is set for "handshaking" with the SPS 4001B sequencer, the Oxymitter 4000
sends a signal to the sequencer. The sequencer automatically performs a
calibration upon receiving the signal. Therefore, no human interface is
required for the automatic calibration to take place.
See Figure 1-3. When a calibration is required, the Oxymitter 4000 sends a
signal to the programmable logic device (PLD) on the interface board of the
sequencer. The PLD energizes the calibration gas 1 (high O
2
) solenoid.
Calibration gas 1 then flows through the sequencer to the Oxymitter 4000.
The Oxymitter 4000 measures the oxygen content of calibration gas 1 and
sends a signal to the sequencer indicating that it received the gas. When the
sequencer receives the signal, the PLD deenergizes the calibration gas 1
solenoid.
Next, the PLD energizes the calibration gas 2 (low O
2
) solenoid, and
calibration gas 2 then flows through the sequencer to the Oxymitter 4000. The
Oxymitter 4000 measures the oxygen content of calibration gas 2 and sends
a signal to the sequencer indicating that it received the gas. After measuring
the two calibration gases, the Oxymitter 4000 automatically makes an internal
calibration adjustment and sends the signal to the sequencer. When the
sequencer receives the signal, the PLD deenergizes the calibration gas 2
solenoid.