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7060/7061
User's Guide
7.2
22
A brief description of the functions of the buttons follows:
SET – Used to display the next parameter in a menu and to set parameters
to the displayed value.
DOWN – Used to decrement the displayed value of settable parameters.
UP – Used to increment the displayed value.
EXIT – Used to exit from a menu. When EXIT is pressed any changes made
to the displayed value will be ignored.
3)
The on/off switch controls power to the entire bath including the
stirring motor.
4)
The control indicator is a two color light emitting diode (LED). This
indicator lets the user visually see the ratio of heating to cooling.
When the indicator is red the heater is on, and when it is green the
heater is off and the bath is cooling.
5)
The heater power switch is used to select the appropriate heater
power levels for heating and controlling temperatures.
6)
The cooling switch controls power to the refrigeration compressors
and cooling fan.
Refrigeration Controls
The front panel refrigeration control area has four features (see Figure 3
bottom): 7) the cooling power switch, 8) the cooling temperature regulating
valve, 9) the cooling temperature/pressure gauge, and 10) cascade refrigera-
tion indicator lights.
7)
The cooling power switch is used to control the cooling capacity. It
is set to "LOW" power for higher bath temperatures (–20°C and
above). This switch limits the capacity of the refrigeration system so
that the minimum power level for the highest temperature stability
is available.
8)
The cooling temperature regulating valve is used to adjust the cool-
ing temperature at which the refrigerant evaporates, which deter-
mines cooling efficiency. The ideal temperature for operation is
about 5–10 degrees Celsius below the desired bath temperature for
temperatures below –20 to –25°C. Above –20°C, set the cooling
pressure as indicated in Table 2. Refer to the label below the gauge
for approximate pressure and evaporative temperature settings. The
table from the label is reproduced below. DO NOT set the cooling
temperature to a point above the bath temperature. Pressures may
be experimented with to achieve optimum results. However, DO NOT
set the pressure more than 2psi above the recommended setting.
High cooling powers are difficult to control at maximum stability. Re-
fer to the duty cycle setting on the temperature controller. Adjust-
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