Cutout - Fluke 7012 User Manual

7012 Calibration Bath
User's Guide
9.8
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The proportional band should also be wider when the fluid viscosity is higher
because of the increased response time.
The proportional band width is easily adjusted from the bath front panel. The
width may be set to discrete values in degrees C or F depending on the selected
units. The optimum proportional band width setting may be determined by
monitoring the stability with a high resolution thermometer or with the control-
ler percent output power display. Narrow the proportional band width to the
point at which the bath temperature begins to oscillate and then increase the
band width from this point to 3 or 4 times wider. Table 3 lists typical propor-
tional band settings for optimum performance with a variety of fluids at se-
lected temperatures.
The proportional band adjustment may be accessed within the secondary menu.
Press "SET" and "EXIT" to enter the secondary menu and show the heater
power. Then press "SET" to access the proportional band.
S+E
Access heater power in secondary menu
Heater power in percent
12 Pct
S
Access proportional band
Proportional band setting
Pb=0.101C
To change the proportional band press "UP" or "DOWN".
New proportional band setting
Pb=0.060C
To accept the new setting and access the cutout set-point press "SET". Pressing
"EXIT" will exit the secondary menu ignoring any changes just made to the
proportional band value.
S
Accept the new proportional band setting

Cutout

As a protection against software or hardware fault, shorted heater triac, or user
error, the bath is equipped with an adjustable heater cutout device that shuts off
power to the heater if the bath temperature exceeds a set value. This protects
the heater and bath materials from excessive temperatures and, most impor-
tantly, protects the bath fluids from being heated beyond the safe operating
temperature preventing hazardous vaporization, breakdown, or ignition of the
liquid. The cutout temperature is programmable by the operator from the front
panel of the controller. It must always be set below the upper temperature limit