Power Up Enable; Heater Out Display; Output Modes; Closed Loop Pid Mode - Lakeshore 336 User Manual

4.5.1 Heater Outputs 63

4.5.1.2 Power Up Enable

All configuration parameters of the Model 336 can be retained through a power cycle.
Some systems require that the Heater Range is turned off when power is restored. The
power up enable feature allows you to choose whether or not the heater range is
turned off each time the instrument power is cycled. Set the Power Up Enable param-
eter to Off to ensure that the heater range is turned off on power up. Set it to On to
return the Heater Range to its previous setting when power is restored.
Menu Navigation:
Output SetupQOutput (1, 2, 3, or 4)QPower Up EnableQ(Off or On)
Default: Off
Interface Command: OUTMODE

4.5.1.3 Heater Out Display

The heater output can be displayed in units of percent of full scale current or percent
of full scale power. The heater output display on the front panel is displayed in these
units, and the Manual Output parameter is set in these units. Available full scale cur-
rent and power are determined by the heater resistance, max current setting, and
heater range.
The heater output display is a calculated value intended to aid in system setup and tun-
ing. It is not a measured value, and may not accurately represent actual power in the
heater.
Menu Navigation:
Output SetupQOutput (1, 2)QHeater Out DisplayQ(Current or Power)
Default: Current
Interface Command: HTRSET

4.5.1.4 Output Modes

The heater outputs can be configured in one of four output modes: Off, Closed Loop
PID, Zone, or Open Loop. The Off mode prevents current from being sourced to the
given output. Closed Loop PID is the mode most often used for controlling tempera-
ture. Zone mode builds on the Closed Loop mode by providing automatic changing of
control parameters at up to ten different temperature zones. Open Loop mode pro-
vides a means of applying a constant current to the output.
Menu Navigation:
Output SetupQOutput (1 or 2)QOutput ModeQ(Off, Closed Loop PID, Zone,
Open Loop)
Default: Off
Interface Command: OUTMODE

4.5.1.4.1 Closed Loop PID Mode

The Closed Loop PID mode is the most commonly used closed loop control mode for
tightly controlling temperature using the heater outputs of the Model 336. In this
mode the controller attempts to keep the load at exactly the user-entered setpoint
temperature. To do this, it uses feedback from the control input sensor to calculate
and actively adjust the control output setting. The Model 336 uses a control algo-
rithm called PID that refers to the three terms used to tune the control. Refer to sec-
tion 4.4.11 for details on assigning a Control Input for the closed loop feedback. Refer
to section 2.7 and section 2.8 for a detailed discussion of PID control and
manual tuning.
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