Yokogawa Multi Channel Oxygen Analyzer System ZR22/AV550G - Manual (Page 183)

IM 11M12D01-01E 10-21
10. Other Functions
10.5.3 Setting Blowback Start Time
* When mode is set to [Semi-auto]:
Hold time and blowback time should be set.
Hold time is the time required from the end of blowback to the restart of measurement.
Set the time so that a sample gas that flows through the sensor after blowback can
displace the blowback gas in the sensor and thus the output returns to normal. Setting
range is from 00 minute 00 second to 60 minutes 59 seconds. Once the blowback starts
on a channel, its individual analog output is held at a value preset in the Output Hold
Setup and excluded from averaging group calculations until the preset output hold time
has elapsed.
Blowback time is the time for blowback in one channel. Setting range is from 00 minute
00 second to 60 minutes 59 seconds. A timing chart showing blowback time hold time,
analog output status, and blowback gas switching solenoid contact action timing is
provided in Figure 10.26.
* When mode is set to [Auto]:
In addition to the above hold time and blowback time, interval, start date, and start time
should be set. The interval between blowback cycles can be set in the range 000 day 00
hour to 255 days 24 hours. Once blowback is started, it is performed for all installed
channels. Thus blowback interval must be longer than the sum of blowback time and
hold time for all channels.
Start date and start time specify the day and time that auto blowback is first performed.
To set June 21, 2004 at 1:30 pm, set Start date to 21/06/04 and Start time to 13:00.
<Setting procedure>
* When the blowback mode is set to [Semi-auto] on the Blow Back Setup display:
[Hold time] and [Blow back time] items appear. Select [Hold time] and then touch the
Enter key. A numerical data entry display will appear. Enter the desired value and touch
the Enter key. In the same manner, set the blow back time.
* When the blowback mode is set to [Auto] on the Blow Back Setup display:
In addition to [Hold time] and [Blow back time] items, [Interval], [Start date], and [Start
time] items appear. Enter the desired values for each item in the same manner as above.
CAUTION
Observe the following cautions when setting the blowback timing.
1) When blowback is to be started by a contact input signal, you need to set the relevant
contact input signal to Blow back start on the Input Contacts display.
2) Blowback may be delayed or cancelled by status of the affected channel of by the
status of other channels, as explained by Table 10.5.
3) If the (Blowback) Interval setting is shorter than the sum of blowback times plus hold
times for all channels, then the system will be in blowback status when the second
auto blowback cycle attempts to start. In this case, the second auto blowback will be
cancelled.
4) If the (blowback) interval is set to 000 day 00 hour, then auto blowback will not be
performed.
5) If you set the start date before the current date, then auto blowback will not start.