H-25C Instruction Manual
Instruction 3015-0216
39
4.2.4 Leak Rate Measurement in B -type Mode
To measure how much freon gas is leaking from a leak you have found, use auto-zero hold mode.
The instrument goes into this mode when you hold the probe switch depressed.
To measure the leak rate, you basically just hold the probe tip near the site of the leak (within 1 to 5
mm). Note, however, that in practice some differences in technique may be required, depending on
various conditions.
CAUTION : To measure the leak rate, perform the auto-zero operation in the atmospheric gas, then
hold the auto-zero value.
When 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 below the alarm point.
If the H-25C equipped with an alarm contact output, then if the leak rate reaches the alarm point, a
contact signal is output. This contact signal is switched off when the value falls to 20% below the
alarm point.
4.2.5 Leak Rate Measurement in A -type Mode
To measure how much freon gas is leaking from a leak you have found, use pass/fail mode. The
instrument goes into this mode when you hold the probe switch depressed. The procedure for
measuring the leak rate is the same as in B-type mode.
Operation in pass/fail mode is as follows:
•
In pass/ fail mode, the 100% point on the bar graph display becomes the alarm point. The
measured value in the display area is displayed with flashing. The alarm point is the value
selected with the "ALARM" switches. Normally, you will set them to select the highest allowable
value that will pass the leak inspection. You can change the alarm point setting value while the
H-25C is operating. Changing the alarm point will cause the status of the "ALARM' switches to
be displayed in the data display area for about three seconds after the change.
Note : When changing the alarm point, keep in mind its interactions with the "GAIN" switch setting
(Subsection 2.2.9).
•
In pass/fail mode, the instrument holds the last auto-zero value. Therefore, once you have put
the instrument in pass/ fail mode, any changes in the background potential will be treated as leak
rate data.
If the atmosphere does not stabilize thus making it difficult to measure the leak rate, try using B-
type mode (see Subsection 4.2.4).
•
If the leak rate is at or above the alarm point, the speaker will emit an intermittent tone
(frequency: approx. 1000 Hz), and the indicator lamp on the probe will light. The tone and the
lamp are switched off when the value falls below the alarm point. If the H-25C is equipped with
an alarm contact output, then when the leak rate reaches the alarm point, a contact signal is
output. This contact signal is switched off when the value is 20% below the alarm point.
