Fluke 7012 User Manual page 38

8 General Operation
Temperature Controller
signal, amplified, and then fed to a pulse-width modulator circuit which con-
trols the amount of power applied to the bath heater.
The bath is operable within the temperature range given in the specifications.
For protection against solid-state relay failure or other circuit failure, the
microcontroller automatically turns off the heater with a second mechanical re-
lay anytime the bath temperature is more than a certain amount above the
set-point temperature. As a second protection device, the controller is also
equipped with a separate thermocouple temperature monitoring circuit which
shuts off the heater if the temperature exceeds the cut-out set-point.
The controller allows the operator to set the bath temperature with high resolu-
tion, set the cut-out, adjust the proportional band, monitor the heater output
power, and program the controller configuration and calibration parameters.
The controller may be operated in temperature units of degrees Celsius or Fahr-
enheit. The controller is operated and programmed from the front control panel
using the four key switches and digital LED display. The controller may also be
optionally equipped with a serial RS-232 or IEEE-488 GPIB digital interface
for remote operation. Operation of the controller using the front control panel is
discussed in Section 9. Operation using the digital interfaces is discussed in
Section 10.
When the controller is set to a new set-point the bath heats or cool to the new
temperature. Once the new temperature is reached the bath usually takes 10-15
minutes for the temperature to settle and stabilize. There may be a small over-
shoot or undershoot of about 0.5°C.
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