OZONE ANALYZER BMT 965 Manual, Rev. 01/2024
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15
Zeroing can be initiated in the following ways:
pressing the ZERO button with succeeding confirmation
driving the Zero-input (Pin 11) with 24 VDC
via the serial interface in User-Mode by sending the character 'A'
automatically, time controlled by the BMT 965 internal timer (see page 14, Zeroing)
via the serial interface in Link-Mode by sending the command *83#3.14159
from a Windows-PC by using the program BMT 965 Link
The display will show information about zeroing. In each zero cycle the dirtiness of the cuvette is
determined. This value is displayed on the front panel and sent via the serial interface. Increased
dirtiness will lead to a Dirty Warning or a Dirty Error respectively (see page 33).
During the whole zeroing action the last measured concentration result is used to set the analog
outputs to a constant value. The serial interface in User-Mode sends out the last measured concen-
tration and, instead of dirtiness, the string 'AAAA'.
Automatic Zeroing with Control of Purge Gas
Purge gas control can be taken over by the BMT 965. The relay contact Purge (Pin 2) is used for
this purpose. This contact (max. 28 V, 0.5 A) can switch an ozone proof solenoid valve to switch
from ozone to an ozone free gas like CDA (Compressed Dry Air) or Oxygen. Alternatively, the
instrument can be ordered with a built-in Internal Purge Unit. In both cases the parameter Aut
Zero Interval has to be set to a time interval between 1 hour and 99 hours (either by use of the
front panel menu, the program BMT 965 Link or the Link-Mode command *45#). Automatic
zeroing will be activated after this time interval. Additional zero cycles can be initiated within this
interval by the methods described above, which reset the built in Zero-Timer.
In case Auto Zero Interval is set higher than zero (1 to 99 h), there will be an additional automatic
zero cycle approx. 15 minutes after each power up. Also, the purge contact is activated on each
zeroing cycle (only if Auto Zero Interval > 0 h).
Attention: Activation of the Automatic Zeroing with Control of Purge Gas is meaningful only if
the relay contact Purge (pin 2) is used to somehow activate purging of the cuvette in order to
remove any ozone or with a built-in Internal Purge Unit.
One complete automatic zero cycle needs 20 seconds. It consists of three phases:
1. purge period, 10 seconds (the instrument displays Purging...)
2. zero calculation, 2 seconds (it displays Zeroing... and the calculated cuvette dirtiness)
3. waiting period, 8 seconds (it displays Sampling...), during which the cuvette is refilled with
ozone.
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