4.6.1 Heater Outputs
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Default: 0%
Interface command:
MOUT
4.6.1.5.6 Setpoint
Use the setpoint parameter to set the desired load temperature for a control loop.
Before entering a setpoint, a control loop must be created by configuring an input
sensor and assigning it to a control output using the control input parameter. The set-
point can be entered in either temperature units or sensor units, based on the sensor
input’s Preferred Units setting. The setpoint ramping feature is available when con-
trolling in temperature units to provide smooth, continuous control from one tem-
perature to the next. Refer to section 4.4 for details on Input Setup. Refer to
section 4.6.1.5.1 for details on assigning a control input. Refer to section 4.6.1.5.7 for
details on the setpoint ramping feature.
Most applications require control in units of temperature. To control in units of tem-
perature, set the preferred units parameter of the control input sensor to kelvin
(section 4.4.11). When controlling in temperature, the available setting range of the
setpoint is limited by the setpoint limit parameter of the assigned temperature curve.
Refer to section 5.6.1 for details on setting a curve setpoint limit.
The setpoint limit feature only limits the setpoint entry. For even greater protection, the
temperature limit feature can be used to turn off all heater outputs if a sensor reading
above the specified temperature is observed (section 4.4.10).
There are some instances when temperature control in ohms may be desired, for
example when a temperature curve is not available. For these applications the
Model 372 can control temperature in ohms. To control in ohms, set the preferred
units parameter to ohms. When controlling in ohms, the setpoint resolution matches
the display resolution for the sensor input type given in the specifications (section
1.6.1).
Temperature control in sensor units can be unpredictable since most resistive tempera-
ture sensors do not have a linear response to temperature, and therefore, can have differ-
ent sensitivity in different temperature ranges.
If you change the preferred units from ohms to temperature (kelvin), or from tem-
perature to ohms, the Model 372 uses the assigned temperature curve to convert the
setpoint to the new control units. This provides minimal disruption in the control out-
put if you change the preferred units parameter while the control loop is active.
To change the setpoint, first configure the output mode of the desired heater to
Closed Loop PID mode (section 4.6.1.4). Then press
Sample Heater
or
Warm-Up
Heater
to display the respective control loop information if it is not already displayed.
Then press
Setpoint
.
Menu navigation:
Setpoint
Q
(See note below)
Default: 0.0000 K
Interface command:
SETP
When controlling in temperature, setpoint is limited by the control input temperature
curve’s setpoint limit. When controlling in sensor units, setpoint is limited by the limits of
the configured control sensor.