1735 Technical Manual - Novatech Controls

4.23 Dust in the Flue Gas
For heated probes the preferred method of mounting for dust-laden applications is facing vertically
downwards with the filter removed. Probes can also be mounted horizontally with no filter with some dusts.
An occasional automatic back purge is helpful in this case.
Normally heated probes are supplied with filters for applications with particulates in the process gas. The
probe response time should be tested when the probe is first installed, and then regularly until it remains
constant for a significant period. Filter purging should be set up on the time periods determined by these
tests. To test the probe response time, use a stopwatch to obtain the time for a probe to achieve a 63 %
change from one reading to another. If a probe filter blocks completely in a short period of time, then there is
no option but to use the probe without the filter. A trial probe with filter can be installed to test whether a filter
blockage is likely to occur.
4.24 Connecting a Pressure Transducer
If the process gas pressure varies more than 4" WG and therefore requires automatic compensation,
connect a pressure transducer as shown below.
Place a link across LK2, near to the input terminals 24 & 25. If the link is not populated, you can achieve
the same thing connecting a 120Ω resistor across the two terminals.
A pressure change of 4" WG will cause a change in the calculated oxygen reading of approximately 1%.
120ohm Resistor
24 BFT+
25 BFT-
There are no calibration adjustments for the zero or span of the pressure transducer input. Set the
transducer scale range in the commissioning menu - See Section 7.2.10. The pressure can be displayed on
the lower line by enabling the corresponding option. See Section 6.3.2.
April 2012
32 1735 Water Vapour Transmitter