Model 106-H Ozone Monitor Manual Rev. D-2
19
With these settings, the relay will close (pass current) until the ozone concentration
exceeds 5.10 wt% O
2
. Above this concentration, the switch relay will open. The relay
will not close again until the ozone concentration drops below 4.90 wt% O
2
. In this
way, for example, the ozone concentration from an ozone generator could be
controlled in the range 4.9 to 5.10 wt% O
2
. You may now move the cursor using the
Select switch to choose the digits in the On and Off relay settings: choose a digit to
change by depressing the Select switch, and rotate the Select switch to change those
settings. To choose another digit to change, depress the Select switch again to
remove the blinking cursor. The units of the relay limits may be changed by entering
the
Admin / Cfg / Unt
submenu and selecting the desired units (see Section 3.9).
Physical connection to the relay is made by means of a supplied screw connector for
attaching wires to your device. The center terminal is common. When viewing the
connector from the rear of the instrument, the terminal on the right is in normally open
(i.e., it closes when the ozone concentration is below the first set point). This is the
connection you would ordinarily use. The screw connector on the left is normally
closed; i.e., it behaves in the opposite manner as the right screw terminal.
Please see our
Technical Note 45
for a detailed description of connecting to the relays
and using them to control an ozone generator, alarms, or for creating a system
override (
https://twobtech.com/docs/tech_notes/TN045.pdf
).
3.19 Lamp Test
If the instrument is excessively noisy (standard deviation greater than 0.02 wt%), or
always reads near zero in the presence of ozone, or if the
Low Lamp
light is turned
on, it is useful to perform the lamp test to make sure that the lamp is turning on and
does not fluctuate too rapidly. Before performing the lamp test, allow the instrument to
warm up for at least twenty minutes.
Choose
Lmp
from the
Admin
Menu
.
The display will momentarily read “
Lamp Test
”.
The photodiode voltages will then be displayed, for example:
Smp=1.24578 V
Ref=1.50364 V
The photodiode voltages (PDV) are a measure of the lamp intensity and should be in
the range 0.6-2.2 volts. Since absorbance is a ratio measurement, the absolute value
of the voltages is not particularly important. However, above 2.5 volts, which could
occur if the instrument is allowed to become too hot, the photodiode is saturated and
the calculated ozone concentration will be zero. Photodiode voltages less than 0.6
volts without any ozone in the cell are indicative of either a weak lamp or a dirty
detection cell and may result in a noisy measurement. Photodiode voltages will
typically increase as the instrument warms up. Lamp drift is continuously monitored
and corrected for in the firmware and thus has very little effect on the measured ozone
concentration. If your lamp fails the lamp test during the first year of operation,
contact us for a new lamp under the instrument warranty.
