2.5
User Calibration
- Display Offset
Each unit is calibrated in the factory before shipment. The user can still modify the calibration in the field.
The basic calibration of the controller is highly stable and set for life. User calibration allows the user to offset
the permanent factory calibration in order to:
!
Calibrate the controller to meet a user reference standard.
!
Match the calibration of the controller to that of a particular transducer or sensor input.
!
Calibrate the controller to suit the characteristics of a particular installation.
!
Remove long term drift in the factory set calibration.
There are two parameters: Offset Low (OFTL) and Offset High (OFTH) for adjustment to correct an error in
the process value.
There are two parameters for the sensor input
.
These two signal values are CALO and CAHI.
The input
signal low and high values are to be entered in the CALO and CAHI parameters respectively.
Refer to
section 1.6
for key operation and
section 1.7
for the operation flowchart. Press and
hold the
key until the setup Menu page is obtained. Then, press and release the
key to navigate to
the calibration low parameter OFTL. Send your low signal to the sensor input of the controller, then press
and release the
key. If the process value (the upper display) is different from the input signal, the user
can use and
keys to change the OFTL value (the lower display) until the process value is equal to the
value the user needs. Press and hold the
key for 5 seconds to complete the low point calibration (the
display should blink once).
The same procedure is applied for high scale calibration.
As shown below, the two points OFTL and OFTH construct a straight line.
For the purpose
of accuracy, it is best to calibrate with the two points as far apart as possible. After the user calibration is
complete, the input type will be stored in the memory. If the input type is changed, a calibration error will
occur and an error code
is displayed.
2-3.Two Point User Calibration
2.6
Digital Filter
In certain applications the process value is too unstable to be read. To improve this, a
programmable low pass filter incorporated in the controller can be used
.
This is a first order filter with a time
constant specified by the FILT parameter.
A value of 0.5 seconds is used as a factory default.
Adjust FILT
to change the time constant from 0 to 60 seconds.
0 seconds represents no filter applied to the input signal.
The filter is characterized by the following diagram.
1
4
