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H25-IR Preparing for Operation
Instruction 3015-4342 17
2.5.6 Search Auto Zero
The SEARCH AUTO ZERO function allows the operator to select one of the following conditions when the
auto-zero function is disabled while in the Search mode:
NOTE: This function works in conjunction with the setpoint value as entered in Section “
2.5.5 Setpoint.”
ALWAYS ON – The background gas level is always zeroed. If the probe is held over a gas leak, the
instrument will automatically zero-out the reading.
ALWAYS OFF – The background gas level is never zeroed. If the probe is held over a gas leak, the
instrument will not zero-out the reading, similar in operation to the Measure mode.
BELOW SETPOINT – The auto-zero function is ON when the leak-rate is below the setpoint value. If the
leak rate goes above the setpoint value, then the auto-zero function turns OFF, allowing the probe to stay
on the leak without the reading being zeroed-out.
For example: If the Setpoint is 2 Oz/yr, then the auto-zero function is ON for leaks rates that are
<2 Oz/yr. If the leak rate is ≥2 Oz/yr, then the auto-zero function turns OFF.
BELOW 90% OF SP – The auto-zero function is ON when the leak-rate is below 90% of the setpoint value.
If the leak rate goes above 90% of the setpoint value, then the auto-zero function turns OFF, allowing the
probe to stay on the leak without the reading being zeroed-out.
For example: If the Setpoint is 2 Oz/yr, then the auto-zero function is ON for leaks rates that are
<1.8 Oz/yr. If the leak rate is ≥1.8 Oz/yr, then the auto-zero function turns OFF.
BELOW 75% OF SP – The auto-zero function is ON when the leak-rate is below 75% of the setpoint value.
If the leak rate goes above 75% of the setpoint value, then the auto-zero function turns OFF, allowing the
probe to stay on the leak without the reading being zeroed-out.
For example: If the Setpoint is 2 Oz/yr, then the auto-zero function is ON for leaks rates that are
<1.5 Oz/yr. If the leak rate is ≥1.5 Oz/yr, then the auto-zero function turns OFF.
BELOW 50% OF SP – The auto-zero function is ON when the leak-rate is below 50% of the setpoint value.
If the leak rate goes above 50% of the setpoint value, then the auto-zero function turns OFF, allowing the
probe to stay on the leak without the reading being zeroed-out.
For example: If the Setpoint is 2 Oz/yr, then the auto-zero function is ON for leaks rates that are
<1 Oz/yr. If the leak rate is ≥1 Oz/yr, then the auto-zero function turns OFF.
2.6 Calibration
The H25-IR has been calibrated at the factory, and should not require frequent calibrations when
searching for gas leaks. When making measurements, however, the instrument should be calibrated on a
periodic basis to ensure that it meets its published accuracy specification.
Instructions on how to calibrate the instrument are contained in Section
3 Calibration.
SEARCH AUTO ZERO
SETUP NO.1
< ALWAYS ON
ALWAYS OFF
BELOW SETPOINT
BELOW 90% OF SP
BELOW 75% OF SP
BELOW 50% OF SP