Note:
Also on the edge of the PC board are two adjustment
potentiometers, R7 and R8, and a 3-pin terminal TB1.
Pot R7 is for tweaking the 4 mA output level. Pot R8 is
for tweaking the 20 mA output level. These two pots are
factory-adjusted, and the user normally should not have to
adjust them. It is best to leave these two pots alone.
The user normally should not have to disconnect the
3-wire cable from the SG1000E. But if they do so, they
must reconnect the 3-wire cable to the SG1000E as
follows:
• Power supply (+24Vdc) terminal red wire to TB1-1.
• 4-20mA signal clear wire to TB1-2.
• Power supply (-) terminal black wire to TB1-3.
2) Before entering Calibration Mode, set the direction
switch SW1 on the SG1000E’s PC board to the proper
position for the application.
SW1 tells the SG1000E the direction the encoder turns,
CW or CCW, as the process is moved from the fully-closed
to the fully-open position. The CW or CCW direction is
defined via the viewer looking at the back-cover-end of the
enclosure, and not the encoder-shaft-end of the enclosure:
• If the encoder shaft turns in the CW direction as the
process shaft is moved from the fully-closed to the fully-
open position, then set SW1 to the OFF position (i.e.,
toward the center of the PC board). See Figure 4.
• If the encoder shaft turns in the CCW direction as the
process shaft is moved from the fully-closed to the fully-
open position, then set SW1 to the ON position (i.e.,
toward the edge of the PC board). See Figure 4.
Note:
The direction switch SW1 is monitored only briefly as
the SG1000 enters into Calibration Mode. But once
inside Calibration Mode, SW1 is no longer relevant.
Hence, changing SW1 at this point has no effect.
Because of this, SW1 must be set to the desired
position before Calibration Mode is entered in order
to capture the desired setting of SW1.
3) There are two ways to enter Calibration Mode:
• One, remove the +24Vdc power, press-in and hold the
calibration switch SW2, then reapply the +24Vdc power.
(This is referred to as “power-up” entry into calibration
mode).
• Or two, while the SG1000 remains powered, press-in
and hold the calibration switch SW2, for a constant 5 to
6 seconds. (This is referred to as “on-the-fly” entry into
calibration mode).
(Do not press SW2 multiple times or allow it to change state,
just keep it pressed-in). Continue to keep SW2 pressed-in
for a few seconds until the SG1000 outputs a constant 12 mA
from its signal line, then release the button.
The SG1000E is now in the calibration mode
.
4) Move the process shaft to the fully-closed position (i.e.,
0% open).
5) Momentarily press the calibration switch SW2.
• This captures the present encoder count. This value is
then used for the fully-closed position (0% open).
• The output signal remains at 12 mA.
6) Move the process shaft to the fully-open position (i.e.,
100% open).
Note
: As the process shaft moves from fully-closed to fully-
open, the SG1000E’s encoder shaft must turn at least
5.6º, but not more than a 130º turn. Hence, if the
shaft turns more than 130º, or less than 5.6º, then the
SG1000E will
not
work properly for the application.
7) Momentarily press the calibration switch SW2.
• This captures the present encoder count. This value is
then used for the fully-open position (100% open).
•
The SG1000E then automatically exits the calibration
mode and enters the normal operating mode.
Note:
The calibration mode is exited at this point for both
valid and invalid calibrations.
For a valid calibration: If the user does not
immediately move the process shaft, then the
output signal is 20 mA. (Because the process shaft
was left in the fully-open position from step 6, the
output signal is at 100%, which is 20 mA).
For an invalid calibration: The output signal
remains at 12 mA.
See the “
Valid Calibration”
and
“Invalid Calibration”
sections
below for details regarding whether, or not, your
SG1000E accepted the process shaft’s two calibration
positions.
8) Replace the back-end-cover onto the SG1000E.
This ends the calibration procedure.
Valid Calibration (Normal Operating Behavior)
Assuming the user followed the calibration procedure
correctly
,
the SG1000E behaves as follows:
• When the process shaft is at the fully-closed position (0%
open), the output signal is 4 mA.
• When the process shaft is at the fully-open position (100%
open), the output signal is 20 mA.
• Any process shaft position between 0% open and 100%
open is represented by the output signal being proportionally
between 4 mA and 20 mA.
• If the process shaft is moved to a position that is slightly
beyond (outside of) the fully-closed (0% open) calibrated
position, then the output signal remains at 4 mA. This is
known as 0% ‘run-out’, and it holds to a certain point. If
the encoder is turned far enough beyond the fully-closed
calibrated position, then the encoder “wraps-around” and the
output signal jumps to the fully-open value of 20 mA.
2-4
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Website: www.electro-sensors.com
990-002440 Revision D
