Dwyer Mark User Manual
Page 19
18
CIRCUIT BOARD FEATURES
•
Two test points are provided as a convenience for attaching a HART
®
communication master.
•
The WP (write project) shunt enables and disables the ability to change configuration settings. It can prevent
unintended configuration changes from an accidental press of the ZERO or SPAN button and from communications
with a HART
®
communication master. Set this shunt to ON to prevent configuration changes. Set this shunt to OFF
to allow configuration changes.
•
The FAULT shunt determines whether the transmitter fails high or low in a fault condition. When set to high the
transmitter will output 21.0 mA in a fault condition. When set to low the transmitter will output 3.6 mA in a fault
condition. The transmitter will output 3.8 mA and 20.5 mA when operating normally.
•
The FIND shunt determines if the transmitter will respond to a FIND command. When set to ON the transmitter
will respond to a HART
®
communication master’s Find Command. When set to OFF the transmitter will ignore FIND
commands. This is useful for allowing a HART
®
communication master to discover the transmitter.
•
The LED will flash in response to a HART
®
communication master’s Squawk Command. This is useful for identifying
a transmitter attached to a HART
®
communication master.
CALIBRATION
A. Place the WP shunt in the OFF position if necessary to allow calibration to be performed.
B. Set the valve at the position where you want the meter to read 0% (that is 4 mA). Press and hold the ZERO
pushbutton for two seconds or use a HART
®
communication master to set the ZERO point.
C. Turn valve to opposite position where meter should read 100% (20 mA). Press and hold the SPAN push button
for two seconds or use a HART
®
communication master to set the SPAN point.
D. Reposition the WP shunt if desired.
See Pages 19-25 for wiring procedure, intrinsic safety parameters, relevant warnings and schematics.
* OPTIONAL, MAYBE CONNECTED TO TEST POINT AS SHOWN OR TO SCREW TERMINALS
** REQUIRED FOR HART
®
COMMUNICATIONS, OPTIONAL OTHERWISE
FIND SHUNT
FAULT SHUNT
WP SHUNT
SQUAWK LED
TEST POINT
4-20mA
METER
+
-
-
+
**250Q
HART
®
*
COMMUNICATION MASTER
24VDC
POWER
SUPPLY