Press “SET” to accept the new scan rate and continue.
S
Accept scan rate
9.4
Secondary Menu
Functions which are used less often are accessed within the secondary menu.
The secondary menu is accessed by pressing “SET” and “EXIT” simulta-
neously and then releasing. The first function in the secondary menu is the
heater power display. (See Figure 4 on page 36.)
9.5
Heater Power
The temperature controller controls the temperature of the bath by pulsing the
heater on and off. The total power being applied to the heater is determined by
the duty cycle or the ratio of heater on time to the pulse cycle time. By knowing
the amount of heating the user can tell if the calibrator is heating up to the
set-point, cooling down, or controlling at a constant temperature. Monitoring
the percent heater power will let the user know how stable the bath temperature
is.
The heater power display is accessed in the secondary menu. Press “SET” and
“EXIT” simultaneously and release. The heater power will be displayed as a
percentage of full power.
10.00C
Bath temperature
S+E
Access heater power in secondary menu
SEC
Flashes
12.0 P
Heater power in percent
To exit out of the secondary menu hold “EXIT”. To continue on to the propor-
tional band setting function press “EXIT” momentarily or “SET”.
9.6
Proportional Band
In a proportional controller such as this the heater output power is proportional
to the well temperature over a limited range of temperatures around the
set-point. This range of temperature is called the proportional band. At the bot-
tom of the proportional band the heater output is 100%. At the top of the pro-
portional band the heater output is 0. Thus as the temperature rises the heater
power is reduced, which consequently tends to lower the temperature back
39
9 Controller Operation
