Yokogawa EJA440E - Manual (Page 57)

<4. Diagnostics>
4-10
IM 01C25T01-06EN
NOTE
When setting ILBD parameters in the transmitter
via “Online Parameter” of the EJX HART 5
DTM based on FDT1.2 menu, Diag Mode
automatically changes to 0 (Stop). After the
setting, Diag Mode automatically returns to the
original value.
NOTE
When setting ILBD parameters in the transmitter
via “Download to device” of the EJX HART 5
DTM based on FDT1.2 menu, Diag Mode
automatically changes to 0 (Stop).
 Diag Period
The values such as Ratio fDP and BlkF are
averaged based on several hundreds of pressure
fluctuation values in constant time. Diag Period
defines the sampling time is. The default value at
the shipment is set to 180 seconds.
• Procedure to call up the display
DD and DTM
(excluding EJX_
HART 5[1.2])
[Root Menu] → Diag/Service
→ Diag Parameters → ILBD
Parameters → Configuration →
Diag Period →
EJX_HART 5[1.2]
DTM
Diag and Service → Advanced Diag
Configurations → Impulse Line
Blockage Detection → Diag Period
→
For the information on how to change the sampling
period, refer to subsection 4.2.2.10.
 Diag Supp Count
When the value as Ratio fDP or BlkF exceeds
the threshold value for several times in a row,
it is estimated that the impulse line is plugged.
Diag Supp Count defines the number of times to
estimate blockage detection.
• Procedure to call up the display
DD and DTM
(excluding EJX_
HART 5[1.2])
[Root Menu] → Diag/Service
→ Diag Parameters → ILBD
Parameters → Configuration →
Diag Supp Count →
EJX_HART 5[1.2]
DTM
Diag and Service → Advanced Diag
Configurations → Impulse Line
Blockage Detection → Threshold →
Diag Suppress Count →
If Diag Supp Count is set to three times, an
alarm is not generated at part ‘A’ in Figure 4.4.
Because the first and second values only exceeded
consecutively the threshold.
When the value exceeds consecutively the
threshold value three times, an alarm is generated
(see part ‘B’ in Figure 4.4).
B A A A
B B B A
F0406.ai
Diag Supp Count (Number of times: 3)
Diag Supp Count (Number of times: 3)
Diag Period
Diag Period
Upper Threshold
(Ex. Lim fDPmax)
Lower Threshold
(Ex. Lim fDPmin)
An alarm is generated.
An alarm is generated.
Time
Time
Figure 4.4 Relationship of Diag Supp Count and
Alarm
The number of detection to give an alarm is set for
each blockage detection function. The default value
at the shipment is set to three times.
If fluctuating around the threshold value, an alarm
may be often generated. In this case, change the
threshold value (Limit parameter) or the sampling
time ( Diag Period) to enhance the accuracy of the
blockage detection. Refer to subsection 4.2.2.10.