11
5.
Zero Calibration:
After installation, or throughout the sensor’s lifetime, the sensor signal may
periodically drift from 0.0 ppm even though no gas is present. To reset this press the
key to
increase the value and press the
key to decrease the value on this screen. The keys must be
pressed one at a time to move the value, pressing and holding will have no effect. Wait at least
10 seconds after a new zero has been entered to confi rm signal stability. A bump test should be
performed after calibration.
Warning:
The zero calibration should only be adjusted if the sensor is offset by 5% or less from
zero. Confi rm that no gas is present prior to recalibration and always ensure adequate safety
procedures are enacted to confi rm there is no gas present. If the value is offset by more than 5%
do not recalibrate and consult Hydro Instruments for more information.
6.
Channel Gas Type and Units:
This screen allows the user to enable the sensor channel by
changing the gas type from “OFF” to one of the following options “NH
3
”, “O
2
”, “O
3
”, “SO
2
”,
“Cl
2
”, “ClO
2
”, “CO”, “H
2
”, and H
2
S”. The gas type must match that which the sensor is designed
to detect.
7.
Channel Full Scale:
This screen allows the user to adjust the full scale of the monitor channel,
so that it will match the full scale of the sensor output connected to the channel. Should the two
outputs be misaligned, improper operation will result. Standard full scales for sensors supplied
by Hydro Instruments can be seen in Table 1. If unsure about the full scale output of a sensor,
please contact Hydro Instruments.
TABLE 2: Standard Ranges For Hydro Instruments Gas Sensors
Gas Type
Sensor Range
Chlorine (Cl
2
)
0-10 ppm
Sulfur Dioxide (SO
2
)
0-30 ppm
Ammonia (NH
3
)
0-100 ppm
Other
Consult Factory
8.
Channel Span Calibration:
The gas detector system is factory calibrated and does not require
calibration upon installation setup. Span calibration is rarely required, however, it may be
required or desired to perform span calibrations periodically over the life of the sensor. If
calibration is to be carried out, then the appropriate span gas calibration kit must be purchased
(Figures 7 and 8).
8a. The calibration cap must be installed on the sensor and connected as indicated in Figures 7
and 8. Span gas must be allowed to fl ow at 500 cc/min for at least 1 or 2 minutes until the
displayed reading stabilizes. The reading on this screen should be adjusted to match the
ppm value of the span gas being used. Use the
key to increase the reading of the
key
to decrease the reading. Press and release the keys one at a time. Do not press and hold the
keys. After adjusting, wait 10 seconds to confi rm that the reading is stable before proceeding
to the next step.
