Yokogawa EJX930A - Manual (Page 45)

<6. Explanation of Basic Items>
6-4
IM 01C25T02-01E
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.
Adjustment of static pressure signal:
The zero/span adjustment function can be used
for static signals, as in the case of pressure
/differential pressure signals. However, the zero-
point adjustment by the external screw function is
not supported for static pressure signal.
Automatic adjustment
The value of the static pressure exerted on the
point where adjustment is to be made is assigned
to parameters (CAL_SP_POINT_LO, CAL_SP_
POINT_HI). After this assignment is set, the amount
of adjustment is calculated by the transmitter and
automatically updated. The procedure for adjusting
the static pressure signal is the same as that of
pressure/differential pressure signal.
Manual adjustment
From the exerted pressure and the output of the
transmitter, calculate the amount of zero/span
adjustment manually and assign the calculated
value to parameters (CAL_SP_DEVIATION_LO,
CAL_SP_DEVIATION_HI).
Selection of static pressure signal type:
Differential pressure transmitters measure the
absolute static pressure. Based on the assumption
that atmospheric pressure is constant, these
transmitters can output signal equivalent to gauge
pressure calculated by deducting the atmospheric
pressure (fixed value) from the measured absolute
pressure. The type of static pressure signal output
to SECONDARY_VALUE and TERTIARY_VALUE
is selected in SP_VALUE_TYPE. SP_VALUE_
TYPE allows selection of gauge pressure or
absolute pressure. When selecting gauge pressure,
set the value of the atmospheric pressure (fixed
value) to ATM_PRESS. The default value of
ATM_PRESS is equal to the value of standard
atmospheric pressure (101.325 kPa).
6.3.5 Functions Relating to Capsule and
Amplifier Temperature
Reference to capsule and amplifier temperature
value:
In CAP_TEMP_VAL and AMP_TEMP_VAL, it
is possible to refer to the capsule and amplifier
temperature value and status. The update period
of this value is about 1 second. The temperature
unit is selected by XD_SCALE.unit of the AI block,
in which CAP_TEMP_VAL is selected. The status
is normally Good-Non Specific. However, in the
case of sensor failure or out of measurement range,
it turns to Bad or Uncertain. For specifics, refer to
Table 8.9.
Determination of the range limit of capsule
temperature:
The range of capsule temperature is from –40 to
120°C. When the measured capsule temperature
deviates from –50 to 130°C range, set the status of
CAP_TEMP_VAL to Uncertain-Sensor Conversion
not Accurate. The status under normal conditions
is Good-Non Specific. Also, set the status of
PRIMARY_VALUE, SECONDARY_VALUE and
TERTIARY_VALUE TO Uncertain-Subnormal.
Determination of the range limit of amplifier
temperature:
The range of amplifier temperature is from –40 to
120°C. When the measured amplifier temperature
deviates from –50 to 95°C range, set the status of
AMP_TEMP_VAL to Uncertain-Sensor Conversion
not Accurate. The status under normal conditions is
Good-Non Specific.