Hach BioTector B3500e, User Manual

Page: 129 / 163

Page 129
8.3.11 Cooler Program
MODE T CONTROL 
MODE defines the operation mode of the Cooler. Cooler
operates automatically with the default TEMPERATURE
CONTROL setting, to achieve the programmed TEMPERATURE
DIFFERENCE below.

When MODE is programmed as PWM “PULSE WIDTH
MODULATION”, the Cooler operates using the BACKUP PWM
DUTY setting below.
BACKUP PWM DUTY 10% 
BACKUP PULSE WIDTH MODULATION DUTY defines the
operation of the cooler in back-up mode, i.e. when there is a
fault with the Cooler or with the BioTector temperature sensor
(i.e. when system generates 107_COOLER FAULT and/or
108_COOLER FAN FAULT or 113_TEMP SENSOR FAULT
warning events). The default 10% setting means that the Cooler
is activated for 10% of the time and deactivated for 90% of the
time.

The BACKUP PWM DUTY mode is automatically cancelled
when the relevant faults are acknowledged in the Fault Archive
menu.
50% PWM OFFSET 14.0C

The 50% PWM OFFSET setting (14°C by default) is the
midpoint offset of the cooler temperature calibration curve, which
is linear. When Cooler operates with PULSE WIDTH
MODULATION at 50%, the Cooler temperature is typically
~14°C below ambient temperature, which is ~25°.
50% PWM SLOPE 5.00%/C 
The 50% PWM slope setting (5% per 1°C by default) is the
slope of the cooler temperature calibration curve at midpoint.
When Cooler operates with PULSE WIDTH MODULATION at
50%, the Cooler temperature changes by ~1°C with every 5%
change in PULSE WIDTH MODULATION.
T DIFFERENCE 16.0C 
TEMPERATURE DIFFERENCE (16°C by default) defines the
temperature difference to be achieved between the BioTector
temperature and the Cooler temperature. BioTector temperature
sensor is located on the O2-Controller Board. Cooler
temperature is achieved with the settings described above.

Cooler Temperature = BioTector Temperature –
TEMPERATURE DIFFERENCE.

When BioTector detects that the Cooler temperature will drop
below 5°C applying above settings, system automatically
decreases the PULSE WIDTH MODULATION so that the
temperature of the Cooler does not drop below 5°C. This is
carried out to avoid possible freezing of the condensate water,
which could be present inside the Cooler.