WIKA CPH6300 - Handbuch (Seite 20)

6 Commissioning, Operation
20 WIKA Operating Instruction, Model CPH6300
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6.4.5 CALC: Pressure change per time dP/dt
(only for sensor 1)
The CALC function “dPdt” allows displaying pressure changes per time directly. The corresponding
measuring intervals (t.int) can be freely chosen. The device automatically saves pressure values
during this period and calculates the pressure change rate (pressure change / time) from the
current measuring value and historical data.
TARE-button: Historical data is deleted, calculation restarts.
Example: Tightness testing for sewage ducts with requirements less than -3 mbar/min in a
5 minutes test duration at a test pressure of 250 mbar.
Equipment/presetting:
■ Sealing bladder and pressure pump
■ Sensor: CPT6200 (measuring range 0 … 1 bar)
■ bASE= Pet.n (minutes) time unit for pressure change rate
■ t.int = 1:00 (1 minutes) test duration, for which the pressure change rate is calculated
■ Logger: Cycl, 5 sek
Realising:
■ Connect all parts, arrange all necessary sealings
■ Start logger
■ Charge with pressure, wait for sufficient time
■ Restart calculation with button “TARE”
■ Current pressure value is displayed, button “SET” changes to dP:dt display
■ The display can give some preliminary information about the test result
(will it fail the test?)
■ Release pressure after 5 minutes
■ Stop logger
Evaluation:
Read out data logger with GSOFT, input at register “comment”:
Client, place of inspection, date, time, address / duct number, as-built data (duct type,
nominal size, etc), test instructions, pressures, tolerances, etc. as well as test result.
Therefore a comment sample can be prepared as file, company logo etc. can be added for
printing.
t.int- setting: If there are set high values the displayed values can be easily
misinterpreted, because the displayed value responds very slowly.
The displayed value is calculated: P(T
current
) – P(T
current
-t.int) / T.int
If there are no data for the whole t.int-period yet the values are extrapolated with the
already available data.
GB