Inficon T-Guard Leak Detection Sensor Uživatelský manuál stáhnout pdf (Strana 47)

Operation 45

jina85e 5.fm Technical Handbook(1112)

Notice If the trigger value is higher than 1x10

-3

mbar l/s per litre of the net volume,

both test samples will be measured in GROSS-mode. Then you must use

outside air to purge the chamber. The helium background on the reference

line must be really stable for GROSS-mode. If this is not possible, a bigger

chamber or diluted helium has to be used to measure in FINE-mode.

Notice If the T-Guard™stops the measurement due to a too high signal in G

ROSS

mode, it reports a leakage rate of a hundred times the highest trigger level.

If it stops in F

INE mode for the same reason, it reports five times the highest

trigger level.

In both cases, the PLC output "GROSSLEAK" is active.

After each accumulation measurement and waiting for a certain time, the chamber

will be purged. You can generally turn this automatic purge process off; it must then

be initiated with a control command every time.

5.3.1.1 Hints for a good measurement:

• Use fans inside the chamber to have a perfect mixture of helium and air

everywhere inside the chamber! The gas flow of the fans should be at least once

the chamber volume per second!

• Purge the test chamber before measurement!

An insufficient chamber purge is indicated with the warning W45.

• For best and repeatable results you must apply outside air to the reference inlet.

In order to have a more stable background on the reference inlet, put it loosely

into a tightly closed buffer volume. This buffer volume reduces the helium

background variations.

• Apply external air on the measurement line during the purge time in order to clean

it.

• You should purge the chamber after every measurement, then purge the

measurement line for at least 4 s, then wait for 2 s before performing the next

measurement. This removes the residual helium, which could affect the following

measurements, from the measurement system.

• The chamber must have neither slots nor holes. It must be sealed with rubber

gaskets. Only then are the measurements free from external influences.

Fig. 6-8 Display after finished measurement in Accumulation mode

1 2 ... 42 43 44 45 46 47 48 49 50 51 52 ... 84 85

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Inficon T-Guard Leak Detection Sensor Uživatelský manuál Strana 47