Watlow Series SD Limit - Manual (Page 43)

Calibration Offset
Calibration offset allows a device to compensate for
an inaccurate sensor, lead resistance or other factors
that affect the input value. A positive offset increases
the input value, and a negative offset decreases the in-
put value.
The input offset value can be viewed or changed with
Calibration Offset [`CAL] (Operations parameters).
Filter Time Constant
Filtering smoothes an input signal by applying a
first-order filter time constant to the signal. The dis-
played value, the controlled value or both the displayed
and control values can be filtered. Filtering the dis-
played value makes it easier to monitor. Filtering the
signal may improve the performance of the limit in a
noisy or very dynamic system.
Select filter options with Input Filter [Ftr;E]. Select
the Filter Value with [FLtr] (Setup Page).
Sensor Selection
You need to configure the limit to match the input
device, which is normally a thermocouple, RTD or
process transmitter. When you select an input device,
the limit automatically sets the input linearization to
match the sensor. It also sets high and low limit values,
which in turn determine the limit set point range-high
and range-low values.
Select the sensor type with Sensor Type [`Sen]
(Setup Page).
Access Lockout
The user’s access to the Operations Page can be con-
trolled through the
[`lOC] parameter. The [`lOC] pa-
rameter appears at the end of the Setup Page. It does
not affect the Setup, Factory or Programming Pages.
[``0] No level of lockout. The user has full access to
all prompts and menus.
[``1] The Programming Page is locked from view.
The Setup Page is locked except for the
[`LOC]
prompt, which can be viewed and changed. The user
will be able to change and view all prompts in the Op-
eration and Factory Pages.
[``2] The Programming Page is locked from view. The
Setup Page will be locked except for the
[`LOC] prompt,
which can be viewed and changed. The user can change
the limit low and limit high set points only. All prompts
except for the
[`L1;LO] and [`L1;HI] in the Operation
Page are locked from view.
[``3] Full lockout of prompts and menus. All
prompts in the Operation and Setup Pages are locked
from view. The operator can use the Reset Key for
clearing limits and alarms, and for silencing alarms.
The operator can also use the ¿Up-arrow and
¯Down-arrow keys to access the [`LOC] prompt in
the Setup Menu, which can be viewed and changed.
Note: For FM Approval, the [`LOC] parameter must be set to 3 or
the limit must be mounted remotely to restrict casual user adjust-
ment.
Unfiltered Input Signal
Time
Temperature
Filtered Input Signal
Time
Temperature
Time
Temperature
Temperature Reading
from Sensor
Actual Process Temperature
Negative Calibration Offset will
compensate for the difference
between the Sensor Reading and
the Actual Temperature
Wa t l o w S e r i e s S D L i m i t ■ 4 1 ■ C h a p t e r 9 F e a t u r e s