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User Manual
Piccolo Range
Parameter
mnemonic
Parameter
Description
Further Information
AL1 Alarm 1 Setpoint Sets the level at which alarm 1 operates See also section 4.4, ‘
AL1.H Alarm 1 Hysteresis Hysteresis sets the difference between alarm 1 switching
on and switching off. It is designed to prevent random
switching if the PV is noisy or changing significantly.
Alarms’
AL2 Alarm 2 Setpoint Sets the level at which alarm 2 operates
AL2.H Alarm 2 Hysteresis Hysteresis sets the difference between alarm 2 switching
on and switching off. It is designed to prevent random
switching if the PV is noisy or changing significantly.
AL3 Alarm 3 Setpoint Sets the level at which alarm 3 operates
AL3.H Alarm 3 Hysteresis Hysteresis sets the difference between alarm 3 switching
on and switching off. It is designed to prevent random
switching if the PV is varying significantly.
A.tUn Auto-Tune Enable. OFF (disable), On (enable). See also section 7.2,
‘Tuning’
Pb Proportional Band Range 1 to 9999 engineering units (e.g O C). Default 20. See also section 7
Ti Integral Time Range OFF, 1 to 9999 seconds (default 360).
‘Control’
Td Derivative Time Range OFF, 1 to 9999 seconds (default 60)
cb.Hi Cutback High Range Auto, 1 to 9999 display units (default Auto = 3*Pb)
cb.Lo Cutback Low Range Auto, 1 to 9999 display units (default Auto = 3*Pb)
Nr Manual Reset Range -100 to 100 (default 0.0)
r2G
HyS
HyS.C
Relative Secondary
(Cool) Gain
Primary Output
Hysteresis
Secondary Output
Hysteresis
Range 0.1 to 10.0 (default 1.0)
Sets hysteresis for all outputs configured for ON/OFF
Heating. It is available for a single action ON/OFF
controller. Range 1 to 3000 display units (0.1 to 3000 or
0.01 to 300.0 depending on the number of decimal
places configured).
Sets hysteresis for all outputs configured for ON/OFF
Cooling in a double action controller. Range 1 to 3000
display units (0.1 to 3000 or 0.01 to 300.0 depending on
the number of decimal places configured).
d.bnd Dead Band Dead Band Between Heating And Cooling; Range OFF,
0.1 to 100% of cooling Pb. (Off = no deadband)
1.PLS
2.PLS
3.PLS
4.PLS
Output 1 Minimum
Pulse Time
Output 2 Minimum
Pulse Time
Output 3 Minimum
Pulse Time
Output 4 Minimum
Pulse Time
See also section 7.2.11.
Time proportioning is a method of delivering power to the load by switching the
output on and off for accurately measured time intervals.
To deliver 50% power the output on period will be the same as the off period.
When set to Auto, the minimum pulse time that can be set is 100ms. A very low power
demand is represented by a short on pulse of 100ms duration followed by a
correspondingly long off time. As the power demand increases the on pulse becomes
longer and the off pulse becomes correspondingly shorter. For a 50% power demand
the on and off pulse lengths are the same (at 200ms on and 200ms off).
The choice of minimum pulse time is determined by two factors:
1. The stability of the control. If the minimum pulse time is set too long then the
process variable will appear to dip during the off times. This may cause apparent
control instability.
2. The life of the control actuator. Relay outputs or mechanical contactors may wear
out prematurely if the minimum pulse time is set too short.
Setting to Auto is suitable for triac or logic outputs, not driving a mechanical device.
If the control device is a relay or contactor the minimum on time should be set greater
than 5 seconds (for example) to prolong relay life.
By way of illustration, the ON/OFF times are shown in the table for a typical relay
setting of 5 seconds and a typical logic setting of 0.1s:-
Power -.PLS Time = 5 seconds
-.PLS Time = 0.1 second (Auto)
demand ON seconds OFF seconds ON ms OFF ms
1% 5 500 100 10,000
10% 5 50 100 1000
25% 6.7 20 130 400
50% 10 10 200 200
75% 20 6.7 400 130
90% 50 5 1000 100
99% 500 5 10,000 100
For relay outputs the range is Auto or 0.1 to 150.0 seconds (default 5.0).
For logic outputs the range is Auto or 0.1 to 150.0 (default Auto = 100ms)
34 Part No HA031260 Issue 1 May -12