4.5.1 Heater Outputs
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4.5.1.7.4 Derivative (D)
The derivative parameter (sometimes called rate) is the D part of the PID control
equation. The derivative time constant should normally be somewhere between
p
and
1/i
the integral time in seconds, if used at all. As a convenience to the operator,
the Model 335 derivative time constant is expressed in percent of ¼ the integral
time. The range is between 0% and 200%. Start with settings of 0%, 50%, or 100%,
and determine which setting gives you the type of control you desire. Do not be sur-
prised if the setting you prefer is 0%. Note that by using a percent of integral time,
derivative scales automatically with changes in the integral value and does not have
to be revisited frequently.
To set D first configure the front panel display to show the desired control loop infor-
mation, then use the
D
key on the front panel. A quick way to access the setting if the
control loop information is not already being displayed is to use the front panel
A
or
B
keys to temporarily display the control loop information while the new setting is
entered. Refer to section 4.3 for details on configuring the front panel display.
Menu Navigation:
D
Q
(0% to 200%)
Default: 0%
Interface Command:
PID
4.5.1.7.5 Manual Output
Manual Output is a manual setting of the control output. It can function in two differ-
ent ways, depending on control mode. In open loop control mode, the Manual Output
is the only output to the load. The user can directly set control output from the front
panel or over the computer interface. In closed loop control mode, Manual Output is
added directly to the output of the PID control equation. In effect, the control equa-
tion operates about the Manual Output setting.
The Manual Output setting is expressed in percent of full scale. Percent of full scale is
defined as percent of full scale current or power on the selected heater range. Refer to
section 4.5.1.5 to set the Heater Out display. Available full scale current and power
are determined by the heater resistance, Max Current setting, and Heater Range.
Manual Output setting range is 0% to 100% with a resolution of 0.01%.
To set Manual Output first configure the front panel display to show the desired con-
trol loop information, and then use the
Manual Out
key on the front panel. A quick
way to access the setting if the control loop information is not already being dis-
played is to use the front panel
A
or
B
keys to temporarily display the control loop
information while the new setting is entered. Refer to section 4.3 for details on con-
figuring the front panel display.
When an output is configured for Open Loop mode, the Manual Output setting is
available in the Output Setup menu. This is because in the Open Loop mode no Con-
trol Input (feedback sensor) is required, and if none is set then there would be no way
to use the
Manual Out
front panel key to set the output, unless you are in the Custom
Display mode. The Control Input parameter can be assigned to a sensor input (that is
not being used for closed loop control) as a means of quickly accessing the Manual
Output setting using the
Manual Out
front panel key.
Menu Navigation:
Manual Out
Q
(0% to 100%)
Default: 0%
Interface Command:
MOUT
