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Limit Controller
A protective device that will shut down a process at a preset Exceed Condition, in order to
prevent possible damage to equipment or products. A fail-safe latching relay is used, which
cannot be reset by the operator until the process is back in a safe condition. This signal may
be applied from the instrument keypad, Digital Input or command via Serial Communication.
Limit controllers work independently of the normal process controller. Limit Controllers have
specific approvals for safety critical applications. They are recommended for any process
that could potentially become hazardous under fault conditions.
Also refer to Annunciator, Controller, Exceed Condition, Exceed Time, Latching Relay, Limit
Hysteresis, Limit Setpoint and Serial Communications.
Limit Hysteresis
An adjustable band on the "safe" side of the Limit Setpoint. For a high limit, the hysteresis
band is below the limit setpoint value, for a low limit, the hysteresis is above the limit setpoint
value. The latching limit relay cannot be reset by the operator until the process has passed
through this band
Also refer to Exceed Condition, Latching Relay, Limit Controller and Limit Setpoint.
Limit Setpoint
The preset value at which an Exceed Condition will occur. When a Limit Controller has been
set for High Limit control action, the Exceed Condition is above the Limit Setpoint. When a
Limit Controller has been set for Low Limit control action, the Exceed Condition is below the
Limit Setpoint.
Also refer to Annunciator, Exceed Condition, Limit Hysteresis, Limit Controller and Setpoint.
Lock Codes
Defines the four-digit codes required to enter Configuration (20), Set-Up (10), and Auto
Tuning (0) modes.
Display codes = ?+"? , :+"? and #+"? , default values shown above in brackets.
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Glossary
- DIN Controllers & Indicators - Product Manual
Type: Limit Controller Definition
Type: Limit Controller Definition
Type: Limit Controller Definition
59305, Issue 5 – March 2005
Type: General Parameter
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