4.6.1 Heater Outputs
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4.6.1.5.8 Setpoint Change Pause Time (Measurement Input Only)
Temperature control loops need time to settle after any setpoint change. If one of the
measurement input channels is assigned to an output for temperature control while
actively scanning, the loop may not get enough time to settle into the new setpoint
before the scanner moves away from the control channel. The Model 372 can be
forced to read only the specified measurement input control channel for a period of
time after any setpoint change to guarantee settling. This time period is set with the
setpoint change pause parameter. The setpoint change pause time parameter is
selectable from 1 to 255 s with a resolution of 1 s. Manually changing scanner chan-
nel will override the pause and force a reading.
Menu navigation:
Output Setup
Q
Sample Heater
or
Warm Up Heater
Q
Setpoint Chng Pause
Q
(1 to 255)
Default: Off
Interface command:
RANGE
4.6.1.5.9 Heater Range
The Heater Range setting is used for turning a control output on, as well as setting the
output power range for the heater outputs. All three outputs provide an Off setting for
turning the output off.
The warm up heater and analog/still outputs do not have multiple output ranges, and
only provide an On setting for enabling the respective output.
The sample heater provides eight ranges of settings which provide decade steps in
power, based on the maximum output power available to the connected heater. The
100 mA range provides the maximum power, and each successive lower range pro-
vides 10 times less power than the last. Lower sample heater ranges are provided to
allow good control resolution at lower temperatures where cooling power dimin-
ishes. Heater range is an integral part of the closed loop control system so re-tuning
may be required when heater range is changed.
The sample heater output range follows the heater output display units of current or
power. An appropriate heater resistance must be entered under the output setup
menu for the power calculation to be meaningful. The maximum current or power is
used on the display to indicate the selected range. Some examples of heater power
versus heater resistance are given in section 3.7.1.1.
While controlling temperature, the following will cause the heater range to automat-
ically turn off:
D
Exceeding the temperature limit setting
D
Setup changes to the control input
D
Power loss with the power up enable feature turned off
D
Input errors such as T. Over, T. Under, S. Over, and S. Under
Available full scale current and power for the heater outputs are determined by the
heater resistance, Max Current setting, and Heater Range.
Specifications of the heater outputs are provided in Chapter 1. Heater theory of oper-
ation is provided in section 2.5. Various heater installation considerations are pro-
vided in section 3.7.
To set the sample heater range, press
Sample Heater
to configure the front panel dis-
play to show the desired control loop information. Then press
Heater Range
. In addi-
tion, the heater range can be selected from the output setup menu.