Riken Keiki GD-3EC, Technical Manual

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6. Alarm Activation 6-5 Functions to ensure correct alarm activation
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6-5 Functions to ensure correct alarm activation
6-5-1 Zero suppression function
The sensors used in the product are susceptible to the effects of ambient fluctuations (e.g., temperature and
humidity characteristics) and interference gases (interference characteristics), which affect the readings given
by the product. Therefore, readings may fluctuate around zero levels even under normal conditions.
The zero suppression function is designed to minimize the effects of these ambient fluctuations and interference
gases around the zero level. Use this function to suppress reading fluctuations below the preset value to give a
zero reading (or [20.9] (vol%) for oxygen).
<Zero suppression function disabled> <Zero suppression function enabled>
The reading fluctuates around the zero
level.
Displays zero up to the preset value.
NOTE

The standard preset value for the zero suppression function differs depending on sensor specifications.

When the detection target gas is oxygen, enabling the zero suppression function will give a reading of
[20.9] (vol%) for fluctuations in the vicinity of 20.9 vol% up to the preset value. Note that the standard
preset value for the zero suppression function is ±0.5 vol% (with respect to 20.9 vol%) when the
detection target gas is oxygen.

In user mode and maintenance mode, this function is disabled and reading fluctuations below the preset
value are apparent.

The zero suppression type is initially set to [CUT]. For information on how to change the zero
suppression type, refer to ‘7-5-9 Zero suppression type setting’.

The positive zero suppression value can be set within the range of 0 to 2/3 of the first alarm setpoint (if
the first alarm setpoint is 25%LEL, up to 16%LEL). The negative zero suppression value can be set
within the range of 0 to 10 % of full scale +1 digit (if the full scale is 100%LEL, -10%LEL+1 digit). (This is
not normally used by the user.)
CAUTION

The negative suppression value (below zero) is subject to suppression corresponding to 5 % of full scale.
The error code "E-1" is displayed if the reading falls below 5% of full scale. Accurate gas detection is not
possible in this state. Check to confirm that no miscellaneous gases are present, then perform zero
calibration.