Yokogawa EJX930A - Manual (Page 44)

<6. Explanation of Basic Items>
6-3
IM 01C25T02-01E
Procedure for automatic adjustment
The procedure for automatic adjustment is as
follows:
F0602.ai
(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.ai
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
adjustment. 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
adjustment 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
Pressure
The static pressure measurement function is unique
to 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.