MKS T3PIA, Инструкция по эксплуатации, Страница: 38 / 70

Chapter Three: Product Overview Trip Points
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Trip Points
The T3P has four software trip points. The trip points are adjustable using digital communication commands,
such that when the pressure rises above or below the specified trip point value, the corresponding trip point
changes state.
The four trip points can be configured to monitor either the pressure value or the valve position; any
combination is acceptable (refer to
Trip Point Source in the MKS Type T3BIA/T3PIA Valves with RS-232
Interface Supplement for more information). In addition, two of the trip points can be mapped to hardware
relays through the Auxiliary connector (refer to Discrete Output Source in the MKS Type T3BIA/T3PIA
Valves with RS-232 Interface Supplement for more information). Refer to Table 11, page 20, for the Auxiliary
connector pin out.
Trip Point Hysteresis
Hysteresis is built into the operation of the trip points to help compensate for the noise inherent in all systems.
Without hysteresis, the noise may cause the trip points to repeatedly switch states, a condition known as
“relay chatter.” Hysteresis is set as a percentage of the current trip point value. The default hysteresis value of
10% can be adjusted with a digital command (refer to
Trip Point Hysteresis in the MKS Type T3BIA/T3PIA
Valves with RS-232 Interface Supplement for more information).
Setting the hysteresis too high creates a deadband around the trip point. The deadband prevents the trip point
from responding to changes in the pressure signal around the trip point. Ideally, the hysteresis should be close
to, but not less than, the peak-to-peak noise. This setting will provide maximum immunity from relay chatter
while providing the best possible accuracy. It may take some trial and error efforts to determine the smallest
hysteresis setting appropriate for your system.
Trip Point Delay
The trip point delay defines the amount of time a trip point alarm condition must exist before the trip point
status attribute reports an ON condition. If the trip point condition exists for a time period that is less than the
specified trip point delay, the trip point status attribute remains OFF. The trip point delay is illustrated in
Figures 11 and 12, page 31.
The trip point delay can be set from 0 to 10,000 msec; the default value is 0. Different trip point delay values
can be set for the trip point(s) (refer to
Trip Point Alarm Delay in the MKS Type T3BIA/T3PIA Valves with
RS-232 Interface Supplement ).