Yokogawa EJA310A - Manual

EJA / EJX
FieldGuide Analog Output Signal
Standard and Namur NE43
FGP-502
Copyright 2009
1st Edition 01/2009
Yokogawa Corporation of America
2 Dart Road; Newnan, Georgia U.S.A. 30265
Yokogawa EJA and EJX series Brain and HART Protocol
transmitters have an Analog Output Signal (4 to 20 mA)
corresponding to the Primary Variable. The Analog Output
Signal is generated from the digital signal supplied by the
DP
harp sensor by a 15 Bit D/A signal converter. This conversion
has a resolution of 0.004%. The transmitters are designed to
drive output signals slightly greater than the 4 to 20mA “Base”
signal. The intention is to set analog alarm thresholds
recognizably beyond the normal operating 4 to 20 mA range,
to indicate measurement out of range, and to set further alarm
thresholds to indicate a fault condition.
Measurement Out-of-Range
Standard Analog Output Signal
Yokogawa EJA and EJX transmitters
Standard Analog Output EJA (with option /F1) and EJX
transmitters are factory set to have an Analog Output – Lower Limit
(AO-LL) and Analog Output – Upper Limit (AO-UL) of 3.6mA and
21.6mA respectively [EJA transmitters without Option /F1 output
limits are 3.2mA to 21.6mA]. This allows for a small amount of
linear over-range process readings. This linear over-range signal is
refer to Signal Saturation. During operation, once the AO-LL or
AO-UL limits are reached, the current signal locks to the respective
limit and the transmitter communicates a Measurement Out-Of-
Range event to the control unit via the locked analog signal and
digital communication (Brain or HART); and the indicator (if
equipped) displays an error code. Once the normal pressure is
regained, the transmitter clears the error codes, unlocks the analog
signal and begins to operate as normal.
Example: An EJA110A or EJX110A transmitter is ranged for
0 to 100 inH
2
O (4 to 20mA).
The Signal Saturation can be controlled by setting the respective
AO-LL and AO-UL. The AO-LL and AO-UL are programmable
within the parameter limits of the transmitter via the digital
communication protocol. Set the limits by entering the value to the
parameter noted below.
Ensure that the control unit receiving the analog signal is setup to
recognize the settings used.
Namur NE43 Analog Output Signal
Yokogawa EJA and EJX transmitters
NAMUR NE43 is a standard used to define the operating AO-LL
and AO-UL values of the analog output signal. Similar to the
Standard analog output signal, Namur NE43 transmitters are
designed to output signals greater than the 4 to 20mA “Base”
signal; allowing for a small amount of linear over-range process
readings (Signal Saturation). Namur NE43 transmitters set the AO-
LL and AO-UL to 3.8mA (-1.25%) and 20.5mA (103.1%)
respectively. Namur NE43 thresholds are set and can not be
programmed to different values through the Digital protocol.
Ensure that the control unit receiving the analog signal is setup to
recognize the Namur NE43 settings used.