Bacharach H-25C, Инструкция

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H-25C Instruction Manual
Instruction 3015-0216
36
4.2 Measurement
4.2.1 Measurement Modes
The H-25C has two main measurement modes, A-type and B-type. Use the MODE switch
to select the mode to be used (see Subsection 2.2.5).
A-type mode is used if there is very little unwanted gas in the surrounding atmosphere and
its concentration is settled, while B-type mode is used if there is a relatively high proportion
of unwanted gas in the atmosphere and its concentration fluctuates. Generally, use B-type
for detecting leaks since there is usually unwanted gas in the atmosphere in the facility
when measuring leaks.
B-type mode has two sub-modes: auto-zero mode and auto-zero hold mode. Auto-zero
mode operates when the probe switch is off (not depressed ). When the probe switch is on
pressed), the instrument operates in auto-zero hold mode.
4.2.2 Searching for the Location of a Leak in B-type Mode
To find the location of a leak, use auto-zero mode (probe switch off ). To identify the location, bring
the probe tip to within 1 cm of the leak for several seconds. The intake flow of the probe is about 4.5
ml/s, with a response time of about one second.
CAUTION : Be very careful that no liquid is sucked into the probe, since this may damage the
instrument.
In auto-zero mode, if the sensor output is greater than or equal to the alarm point set value, the
speaker sounds an intermittent tone ( frequency : 1000 Hz approx. ), and the probe indicator lamp
lights. The tone and the lamp are switched off when the value is 20% below the alarm point.
If the H-25C is equipped with an alarm contact output, then if the leak rate reaches the alarm point, a
contact signal is output. This contact signal is also switched off when the value falls to 20% below
the alarm point.
In auto-zero mode, the background potential is always updated (delay time: 5 to 10 seconds).
Therefore, the indicated value brings back to 0% over several seconds even when a leak is detected.
In this mode, the detection sensitivity cannot be increased such as in search mode in A-type mode.
Note : When the auto-zero function is in operation, the leak rate cannot be measured correctly. To
measure the leak rate, perform the auto-zero operation in the gas concentration of normal
atmosphere, and then hold the auto-zero value ('auto-zero hold mode").
4.2.3 Searching for the Location of a Leak in A-type Mode
To find the location of a leak, use search mode (probe switch off). The procedure for identifying the
location of a leak is the same as in auto-zero mode in A-type mode.
CAUTION: 1. Be very careful that no liquid is sucked into the probe; failure of the instrument
may result
2. If the sensitivity multiplier setting is too low, the instrument may not respond even
if a leak is present. On the other hand, if it is set too high, the instrument may
respond to the ambient gas level, making it difficult to identify the site of the leak.
Freon gas detection is performed by the following actions.
•
In search mode, the 100% point on the bar graph indicator becomes the search mode alarm
point.