Issue
N
C.S.
04.03.20
Trading Estate Farnham Surrey England
Doc. No. TD 120
Page 10 of 25
5.SET UP (Continued)
5.8 Low Current Point and High Current Point Settings. (Continued).
To set LCP, select the LOW parameter in Setup Mode by pressing the UP button until the LOW LED lights continuously. Press
the SET button to select Adjust Mode, and the LOW LED will blink. Adjust the input signal current within the range 4-20mA to
the value you want to define for the Low Current Point – note that changes in input current within the 4-20mA band do not
result in positioner movement at this stage – the positioner holds the actuator at the angle where it was before Adjust Mode
was selected, irrespective of input current. Press the UP or DOWN buttons to move the positioner to the angle you want to
define for the Low Current Point – if you hold the button down continuously, the positioner will traverse the actuator steadily, or
if you give short blips it will move approximately 1/40 degree (one fortieth) for each blip, to allow precise edging into exactly the
required position. When the actuator is in exactly the position you want, and the signal is adjusted to exactly the value you
want (this can be readjusted after the position has been set if you want), press the SET button again to record the signal and
position as the Low Current Point, whereupon the actuator will make a small leap and then settle back to the LCP again, the
positioner will return to Setup Mode, and the LOW LED will light continuously. The positioner will now respond to its input
signal again.
Note: As soon as the SET button is pressed, the LCP position and signal are stored in non-volatile memory, and are retained
even if the positioner is de-energised before leaving Setup Mode.
To set HCP, select the HIGH parameter in Setup Mode by pressing the UP button until the HIGH LED lights continuously.
Press the SET button to select Adjust Mode, and the HIGH LED will blink. Adjust the input signal current within the range 4-
20mA to the value you want to define for the High Current Point – note that changes in input current within the 4-20mA band
do not result in positioner movement at this stage – the positioner holds the actuator at the angle where it was before Adjust
Mode was selected, irrespective of input current. Press the UP or DOWN buttons to move the positioner to the angle you want
to define for the High Current Point – if you hold the button down continuously, the positioner will traverse the actuator steadily,
or if you give short blips it will move approximately 1/40 degree (one fortieth) for each blip, to allow precise edging into exactly
the required position. When the actuator is in exactly the position you want, and the signal is adjusted to exactly the value you
want (this can be readjusted after the position has been set if you want), press the SET button again to record the signal and
position as the High Current Point, whereupon the actuator will make a small leap and then settle back to the HCP again, the
positioner will return to Setup Mode, and the HIGH LED will light continuously. The positioner will now respond to its input
signal again.
Note: As soon as the SET button is pressed, the HCP position and signal are stored in non-volatile memory, and are retained
even if the positioner is de-energised before leaving Setup Mode.
5.9 Reversing Clockwise/ Anticlockwise Sense of the Positioner.
Refer to TD 180 for an illustrated version of this procedure.
The LCP and HCP settings described in the previous section can be used with complete success to reverse the sense of the
positioner, using settings such as the reverse settings listed in Table 1. However, this will not change the direction of
movement on loss of signal – see the next section for how to set this as desired.
5.10 Changing the Direction of Movement on Loss of Signal.
On being de-energised with air supply still fully pressurised (i.e. on disconnection of the signal, or when the signal falls below
3.5mA), the positioner moves the actuator in a direction set by the de-energised position of the servo valve. This direction of
movement is independent of the LCP and HCP settings described in the sections above.
Movement on loss of air pressure is unpredictable for double acting positioners – if position needs to be held on loss of
pressure, then it is necessary to order an external pressure sensing lockout valve assembly, and if a definite end of travel
position is required on loss of pressure, then it is necessary to order a spring return unit.
Title : Installation, Operation & Maintenance Instructions – IS Digital EL Positioner
N – AR7059 / M – AR6971 / L - AR6419 / K - AR6347 / J-AR6096 / H – AR 6082 / G – AR 5487 / F – AR 5608 / E - AR 5293
