Power Control Functions; Heater Control; Cooling Control - Fluke 7008 User Manual

In the following list of commands, characters or data within brackets, "[" and "]",
are optional for the command. A slash, "/", denotes alternate characters or data.
Numeric data, denoted by "n", may be entered in decimal or exponential notation.
Characters are shown in lower case although upper case may be used. Spaces
may be added within command strings and will simply be ignored. Backspace
(BS, ASCII 8) may be used to erase the previous character. A terminating CR is
implied with all commands.

10.4 Power Control Functions

The digital interface is capable of controlling the heating and cooling functions so
that the bath can be remotely operated at any temperature within the range of the
bath. To allow the interface to control the heating and the cooling, the front panel
controls are disabled by 1) switching the heater switch to LOW, and 2) switching
the refrigeration switch to OFF. Otherwise, the interface would not be able to
switch these functions off. The 7008 bath has four control functions with the
digital interface. These are heater power high/low, cooling on/off, and expansion
valve open/closed and back pressure valve open/closed.

10.4.1 Heater Control

To control the heater with the digital interface the front panel heater switch must
be set to LOW (500 W). The heater function is controlled with the "F1" command.
Setting the parameter to 0 sets the heater to LOW (500 W) and setting it to 1 sets
the heater to HIGH (1000 W). Sending "F1" with no value will cause the controller
to return a value showing what the heater setting is. When the heater setting is
changed a pop will be heard as the heater relay opens or closes.

10.4.2 Cooling Control

To control the refrigeration power with the digital interface the front panel re-
frigeration switch must be off. The refrigeration power function is controlled with
the "F2" command. Setting the "F2" value to 0 turns the refrigeration off and
setting it to 1 turns it on. "F2" alone will return 0 or 1 showing the state of the
refrigeration power control.
The "F3" command controls the cooling temperature or expansion valve. As
discussed in Section 8.5 this valve adjusts the cooling temperature which sets
the cooling capacity. Setting "F3" to 0 opens the valve and 1 closes the valve. A
command with no value will return the current value. With the valve open the
cooling temperature is set with the cooling temperature knob labeled "LOW". This
should be adjusted for approximately 5 psi if the bath is to be used as low as -
10 °C. The knob labeled "HIGH" controls the cooling temperature when the
expansion valve is closed. This should be adjusted for approximately 65 psi.
when the valve is closed.
Digital Communication Interface
10.4 Power Control Functions
10
10-7