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Programming Function Blocks and Features
Video Recorder – User Manual 132
Sterilization
The output CVn OV is a “kill time”, F
0
, which quantifies the destruction of microorganisms during a
sterilization process. F
0
represents the number of minutes after which the microorganism population is
decreased by one decimal or log unit. The F
0
formula is:
F
0
= ∑ [dt x (10
(T-T
ref
)/Z
)]
where:
dt = time between F
0
measurements, in minutes. Dt is equal to the scan cycle of the instrument in
minutes.
T = measured temperature input, in °C
T
ref
= reference temperature (121°C typical)
Z = product-dependent temperature constant
This function also compares the calculated F
0
value to the desired F
0
value, F
d
(Preset). When F
0
equals or exceeds F
d
, the function activates its discrete output CVn OS; this output remains ON(1) until
the F
0
calculation is reset via the Reset Input.
The output CVn A2 is the Time Remaining (Tr) at the current temperature to achieve F
d
and is
calculated as follows:
(F
d
– F
0
)
Tr =
_________
10
(T-Tref)/Z
The F
0
calculation will be reset and the F
0
value will remain at zero while the Reset Input is ON(1). The
calculation will resume when the Reset Input goes OFF(0) again.
Table 4-40 describes the Sterilization prompts. See Table 4-2 for additional prompts.
Table 4-40 F
0
Sterilization Prompts
Prompt Range/Selections Definition
OUT LOW LIMIT
OUT HIGH LIMIT
OFF or number Displayed output value will be clamped and will flash
when these limits are exceeded.
RESET OFF, discrete parameter, 0,
1
Reset input
TEMP INPUT OFF, analog parameter,
number
Measured temperature in degrees C
REFERENCE TEMP OFF, analog parameter,
number
Reference temperature
TEMP CONSTANT OFF, analog parameter,
number
Temperature constant Z
DESIRED F0 OFF, analog parameter,
number
Desired F
0
(F
d
)