OZONE ANALYZER BMT 964 Manual, Rev. 04/2021
24
time interval. Additional automatic zero cycles can be initiated within this interval, which reset
the built in Zero-Timer.
In case Autozero Interval is set higher than zero (1 to 99h), 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 Autozero Interval > 0h).
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.
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 dirtyness)
3. waiting period, 8 seconds (it displays Sampling...), during which the cuvette is refilled
with ozone.
During the complete zeroing period of 20 seconds the analog outputs are set to the stored con-
centration value measured immediately before the start of the zeroing cycle. In the User Mode
the RS-232 transmits the same concentration, and 'AAAA' instead of the cuvette's dirtyness.
The above setup shows the components needed for automatic zeroing. It is very important to
provide automatic switching of purge gas, before the Autozero Interval is set to other values than
zero hours! Otherwise, the instrument could possibly calculate the zero value with ozone in the
cuvette. The Autozero Interval is described on page 20.
It should be pointed out, that setting the Autozero Interval to zero hours actually means, that the
analyzer does not go through the purge cycle described above and does not activate the Purge
Control contact! In this case, the user shall never initiate zeroing with ozone in the cuvette. With
the option Internal Purge Unit, or in the cabinet version, the analyzer takes care about switching
to zero gas, itself.
In case the OZONE ANALYZER BMT 964 is equipped with an Internal Purge Unit (solenoid
valve and air pump with particle filter) as an option, e.g. in the model BMT 964 BT (see Appen-
dix B) the terminal 2 may not be connected externally because it is already connected to the in-
ternal 5 VDC power supply!
SOLEN OID
VALVE
DC
POWER
SUPPLY
OZON E AN ALYZER
PURGE
CON TACT
DC
AIR PUMP
DUST
FILTER
AMBIEN T
SAMPLE GAS
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