Emerson Rosemount 644h, Reference Manual

Page: 44 / 78

Reference Manual
00809-0100-4728, Rev HA
December 2002
Models 644H and 644R
4-4
Callendar-Van Dusen equation:
R
t
= R
o
+ R
o
α [t – δ (0.01t-1)(0.01t) – β (0.01t – 1)(0.01t)
3
]
The following input variables, included with specially-ordered Rosemount
temperature sensors, are required:
R
0
= Resistance at Ice Point
Alpha = Sensor Specific Constant
Beta = Sensor Specific Constant
Delta = Sensor Specific Constant
To input Callendar-Van Dusen constants, perform the following procedure:
1. From the
HOME
screen, select 1 Device Setup , 3 Configuration , 2
Sensor Config , 1 Chng Type/Conn , 1 Sensor 1 or 2 Sensor 2. Set the
control loop to manual and select
OK
.
2. Select Cal VanDusen at the
ENTER SENSOR TYPE
prompt.
3. Select the appropriate number of wires at the
ENTER SENSOR
CONNECTION
prompt.
4. Enter the R
o
, Alpha, Delta, and Beta values from the stainless steel
tag attached to the special-order sensor when prompted.
5. Return the control loop to automatic control and select
OK
.
To disable the transmitter-sensor matching feature from the
HOME
screen
select 1 Device Setup , 3 Configuration , 2 Sensor Confi g, 1 Chng Type/Conn ,
1 Sensor 1 or 2 Sensor 2 . Choose the appropriate sensor type from the
ENTER SENSOR TYPE
prompt.
NOTE
When the transmitter-sensor matching is disabled, the transmitter reverts to
either user or factory trim, whichever was used previously. Make certain the
transmitter engineering units default correctly before placing the transmitter
into service.