to rapid wear of relay contacts. For very fast control ways with the respective high switching
frequency a voltage output is therefore of advantage.
P19: Key-lock
The key-lock allows blocking of the control keys. In locked condition parameter adjustments with
keys is not possible. At the attempt to adjust the parameters despite key-lock the message "==="
appears in the display.
P20: Following value display
When this parameter is selected, pressing the SET key display the actual value of the following
input. The value can be adjusted with parameter P21.
P21: Following value correction
This parameter allows the correction of actual value deviations caused for example by sensor
tolerances or extremely long sensor lines. The regulation measure value is increased or decreased
by the here adjusted value.
P22: Leading value display
When this parameter is selected, pressing the SET key display the actual value of the leading
input. The value can be adjusted with parameter P23.
P23: Leading value correction
This parameter allows the correction of actual value deviations caused for example by sensor
tolerances or extremely long sensor lines. The regulation measure value is increased or decreased
by the here adjusted value.
P30: Lower alarm value
P31: Upper alarm value
The exit alarm is a boundary alarm or a range alarm. Both at the boundary alarm and the range
alarm, limit values can be relative, i.e. going along with the setpoint S1/S1’, or absolute, i.e.
independent of the setpoint S1/S1’. Note that in case of differential control the main setpoint
always is formed by the addition of the actual leading value and the adjusted difference value S1. If
setpoint S1’ is activated the new difference value is either S1+S1’ or only S1, depending on
parameter A35.
If only one switching point is required in case of boundary alarm, the not-used second switching
point should be adjusted to a value above or below the control range and the limit values should be
absolute (see parameter A30).
Boundary alarm function (see fig. 3):
The alarm contact is closed if the process
temperature is above the upper or below the
lower boundary value.
Fig. 3:
Boundary alarm, rel. boundaries
Range alarm function (see fig. 4):
Opposite switching behaviour to the boundary
value alarm. The alarm contact is closed if
the actual value remains between the
boundary values.
Fig 4:
Range alarm, abs. boundaries
Summary of Contents for ST48-WHDVM.04
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