Yokogawa DO402 Dissolved Oxygen Analyzer - Manual (Page 60)

IM 12J05D02-01E
5-24 Parameter setting
Control and Alarm Functions
Control output (mA)
:
Pl control on the 2nd mA output.
The 2nd mA output can be configured to give a P/I (proportional and integral)
control output.
The setpoint, proportional band and integral time are each fully
programmable.
- Adjustable parameters
: Setpoint, proportional range and integral time.
Process alarm
: The contact will be switched when the process value reaches a limit.
This can either be a high or low limit.
- Adjustable parameters
: Setpoint for the process value Hysteresis of the switching action Delay time of
the relay (0 to 200 s)
PI duty cycle control (Fig. 1)
: The contact is used to control the time a solenoid valve is opened.
The propor tional control is achieved by opening and closing the solenoid valve
and varying the ratio of on and off time (on, off).
- Adjustable parameters
: Setpoint, proportional range and integral time. Total period of the pulse period
(5 to 100 s)
PI pulse frequency control (Fig. 2)
: The contact is used to control a pulse-driven pump.
The frequency of pulses regulates the pump speed.
- Adjustable parameters
: Setpoint, proportional range & integral time. Maximum pulse frequency (50 to
120/min.)
Wash cleaning of sensors (Fig. 3)
: Contact S3 is used to control the wash cycle, or as a process alarm.
- Adjustable parameters
: Cleaning time or washing time (tw) Recovery time after washing (tr) Interval
time for wash cycle.
The graph shows a typical response curve during washing. The wash and
recovery times need to be set to suit the process.
Fault alarm
: Contact S4 by default set to function as an alarm, indicating that the EXA has
found a fault in the measuring loop. If the self diagnostics of the EXA indicate
a fault or error, the FAIL contact will be switched. In most cases this will be
caused by a malfunction of the measuring loop.
The FAIL contact is also closed when the power is removed.
The “FAIL” contact may also be configured as a fourth process alarm.