TECHNOLOGY

SWITCH DESIGN
The One Series 2-Wire is a microprocessor-based pressure instrument with an extremely low power (patented) design. A digital display gives real-time information and simplifies programming. Because of its unique 2-wire interface and low power design, the One Series 2-Wire can be attached to a PLC, DCS, or many common relays, using only 2 wires

OPERATION
The One Series 2-Wire uses a stainless steel pressure transducer or temperature sensor to provide input to a micro-controller for making switch decisions. Programming and interrogating the One Series 2-Wire is done through two buttons on the faceplate. A sequence of key strokes for programming provides tamper resistance
• The input is filtered, as programmed by the user.
• The value is compared to the programmed set point and deadband
      information.
• The output state is changed if required.
• The digital display is updated.
• The value is recorded, with a new maximum or minimum reading, for later
      interrogation by the user.
• The Plugged Port feature may be activated.

I AM WORKING (IAW^® DIAGNOSTICS)
One Series 2-Wire contains patented IAW^® algorithm, providing both local and remote assurance of switch health, switch status, and fault conditions. Remotely, the switch output can be configured to operate in either the IAW^® (diagnostic) or simple on-off manner. When programmed for IAW^® operation, the contacts have three possible states:

1. remain closed when the switch is functioning properly, and no alarm exists;
2. open for diagnostic fault or power loss; and
3. 25 mS or 100 mS on-off cycling (pulsing) for proper functioning during an
    alarm condition.

PLUGGED PORT DETECTION (Pressure Models only)
The Plugged Port Detection feature, if enabled by the user, monitors the changes in the process variable over time. As long as there is sufficient fluctuation in the process variable the unit will operate normally. If the process variable does not change over the specified time period a Plugged Port condition will be displayed. The user can program the amount of variation and the window of time to be monitored.

The Plugged Port feature records the present value of the process variable. Two thresholds will be calculated (+/- n) as specified by the user and the timer will be enabled. If the process variable stays within the calculated thresholds and the timer expires, a Plugged Port condition is reported. If either of the thresholds are crossed, the timer will be reset and new thresholds will be calculated. The graph below depicts a typical sequence of events.

T₀ Process variable ramp up
T₁ Process variable stabilizes, new thresholds calculated
T₂ Threshold exceeded, new thresholds calculated, timer reset
T₃ Low threshold exceeded, new thresholds calculated, timer reset
T₄ Plugged Port timer expires, Plugged port condition reported
T₅ Plugged Port condition cleared, new thresholds calculated, timer reset
T₆ Low threshold exceeded, new thresholds calculated, timer reset

During a plugged port condition the display will read “PLUG” and the
switch will be set in the “OPEN” state.

Go to page 4 to see specifications.