H-25C Instruction Manual
Instruction 3015-0216
38
[Auto-zero]
The sensor will output some voltage even for pure air. This is called the background voltage (or potential, or level). If
freon and I or other gases are present in the ambient atmosphere, voltage components due to those gases will add to the
background voltage.
The auto-zero function processes the sensor signal so as to make the background voltage serve, electrically, as the
nominal zero point level. The auto-zero function operates when the sensor output in search mode is below the level
equivalent to the search mode trigger point. This also means that any leak in the range where the auto-zero function
operates will not be detected. Therefore, you must exercise care in the use of this feature if it is important to know for
sure whether any leak is present.
[“Calibration Request Operation] (functions in A-type mode)
A “calibration request" displays the flashing message “CAL", and outputs a speaker tone and flashes the probe
indicator lamp in synchronism. After five seconds of this action, the instrument returns to measurement mode display
for 15 seconds, but if you do not perform a calibration within that time, it will output the calibration request again. If
this alternation between calibration request and measurement mode is repeated ten times, the instrument goes into a
standby mode. (Chapter 3 shows the display in standby mode.) To cancel standby mode, press the probe switch once
•
Select B-type Mode for Detecting Leaks (see Subsection 4.2.3)
If the background potential is always varying, this is an effective aid to leak inspection.
