YOKOGAWA DpharpEJX vigilantplant EJX Series - Functions Relating to Static Pressure

IM 01C25T02-01E
6-3
6. EXPLANATION OF BASIC ITEMS
Procedure for automatic adjustment
The procedure for automatic adjustment is as follows:
F0602.EPS
(1) Change the Block mode
Set MODE_BLK to O/S.
(2) Enter zero% pressure
Apply the actual zero% pressure to EJX.
(6) Change the operation mode
Set MODE_BLK to AUTO for normal operation.
(3) Perform zero adjustment
When the value of the applied pressure is written to
CAL_POINT_LO, EJX calculates the amount of
adjustment for zero adjustment. The calculated amount
of adjustment is incorporated into CAL_DEVIATION_LO.
(5) Performance of span adjustment
When the value of the applied pressure is written to
CAL_POINT_HI, EJX calculates the amount of
adjustment for span adjustment. The calculated amount
of adjustment is incorporated into CAL_DEVIATION_HI.
(4) Input pressure for span adjustment
For span adjustment, apply the actual 100% pressure to
EJX.
F0603.EPS
0
0
Calculated Value Calculated Value
Span adjustment point
After zero adjustment
After zero adjustment
After zero/span
adjustment
Input pressure Input pressure
Before zero
adjustment
CAUTION
Span adjustment is a function for adjusting the
gradient with respect to the point of zero adjust-
ment. If that point is not zero, the gradient of
input and output values cannot be accurately
adjusted. Perform span adjustment after zero
adjustment is completed.
Diagnosis of adjustment results:
When the amount of zero adjustment or span adjust-
ment exceeds any of the following adjustment limits,
“AL50: Adjustment range error for pressure/differential
pressure” is displayed.
The conditions for zero/span adjustment are as follows:
<1> The point of zero adjustment is within ±10%
of the capsule range.
<2> The amount of zero adjustment is within ±10%
of the capsule range.
<3> The point of span adjustment is within the
capsule range.
<4> The input and output gradients after span
adjustment are within ±10% of the gradient at
factory setting.
6.3.4 Functions Relating to Static Pres-
sure
The static pressure measurement function is unique to
EJX series differential pressure transmitters. The
pressure transmitter does not have this function.
Reference to static pressure value:
In SECONDARY_VALUE and TERTIARY_VALUE,
it is possible to refer to the H-side static pressure value
and the L-side static pressure value, respectively. The
update period of these values is 100 msec. The
pressure unit is selected by XD_SCALE.unit in the AI
block, in which SECONDARY_VALUE and
TERTIARY_VALUE are selected. The status is
normally Good-Non Specific. However, in the case of
a sensor failure or out of measurement range, it turns
to Bad or Uncertain. For specifics, refer to Table 8.9.
Setting of signal damping for static pressure:
SP_VALUE_FTIME is parameter that set signal
damping for static pressure signals. The unit of the
signal damping is second.
Determination of the range limit of static pressure
signal:
When the static pressure signal exceeds the maximum
working pressure (MWP) of the capsule, set the status
of PRIMARY_VALUE to Uncertain-Subnormal. Also,
set the status of SECONDARY_VALUE and
TERTIARY_VALUE to Uncertain-Sensor Conversion
not Accurate. The status under normal conditions is
Good-Non Specific.