Yokogawa EJX930A - Manual (Page 44)

<6. Explanation of Basic Items>
6-5
IM 01C25R03-01E
Atmospheric pressure automatic setting:
When “Set” is set to the CURRENT_ATM_PRESS_
ENABLE parameter, the present L-side static
pressure can be automatically assigned as the
atmospheric pressure (ATM_PRESS). To make
this assignment, the SENSOR transducer block
must be set to the O/S mode. After the L-side static
pressure has been assigned to ATM_PRESS,
the value of CURRENT_ATM_PRESS_ENABLE
automatically returns to “off.”
6.3.5 Functions Relating to External
Temperature
Reference to external temperature value:
The contact temperature and status of the RTD
connected at EXT_TEMP_VAL can be referenced.
The update period of this value is about 800
mseconds. The external temperature unit is the unit
selected at XD_SCALE.Unit in the AI block where
EXT_TEMP_VAL is selected. Usually, the status
indicates Good-Non Specific; however, it changes
to Bad or Uncertain during a sensor malfunction or
when the measuring range is exceeded. For actual
details, see Table 8.9 Parameter Operations at
Error Occurrence.
Assignment of the damping time constant of the
external temperature signal:
The EXT_TEMP_VALUE_FTIME parameter is
for setting the damping parameter of the external
temperature signal. The setting unit for this
parameter is [seconds].
Judgment of range limit of the external
temperature signal:
When the external temperature signal has deviated
from the measuring range (-200 to 850°C) by 10°C
or more, it is outside the external temperature
specification range, and the status of the external
temperature signal (EXT_TEM_VAL) is set to
Uncertain-Sensor Conversion not Accurate.
Adjustment of external temperature signal:
A zero/span adjustment function is available for the
external temperature signal just like for the pressure
(differential pressure) signal.
Automatic adjustment
The temperature value is assigned to parameters
(CAL_EXT_TEMP_LO and CAL_EXT_TEMP_HI)
with the external temperature sensor immersed
in the temperature to be adjusted. After this
assignment is made, the adjustment amount is
calculated internally by the transmitter and the
adjustment amount is automatically updated. The
procedure for adjusting the external temperature
signal is the same as that of the differential pressure
signal.
Manual adjustment
From the assigned temperature and the output
of the transmitter, calculate the amount of
zero/span adjustment manually and assign the
calculated value to parameters (CAL_EXT_
TEMP_DEVIATION_LO and CAL_EXT_TEMP_
DEVIATION_HI).
Diagnosis of adjustment:
When the adjustment amount exceeds the
following adjustment ranges, “AL52: Out of external
temperature span adjustment amount range/AL52:
Out of external temperature zero adjustment
amount range” generate an alarm. The zero/span
adjustment ranges are as follows:
(1) The ramp for the input/output of two
adjustment points must be within 10% of the
ramp set before shipment from the factory.
(2) The zero point adjustment amount must be
within ±85°C of the temperature set before
shipment from the factory.
(3) The zero point/span adjustment point must
be in the range -210°C to 860°C.
Fixed external temperature mode:
The value obtained from the external temperature
sensor or a user-specified fixed value can be
selected for the external temperature signal. At
the EXT_TEMP_OPTS parameter, select one of
Selection 0 (No): External temperature sensor, 1
(Yes): External temperature fixed value mode, and
2 (Fall Back): Fixed mode at broken wire.
When the external temperature fixed mode or fixed
mode at broken wire is selected, set the fixed value
at FIXED_EXT_TEMP_VALUE.
6.3.6 Simulation Function
There are two simulation functions in EJX
multivariable transmitter; one is the function
commonly offered in F OUNDATION Fieldbus products
to simulate input of each function block for loop
check, and the other is the flow simulation function
to simulate measured inputs for checking the result
of flow calculation.
The simulation function described in this section is
flow simulation function. For the other simulation
function, see ‘7.3 Simulation Function.’