Specifications

CONAX BUFFALO TECHNOLOGIES TSD 43.021
Rev. ORIG
Page 16 of 28
6.4 INPUT FILTERING
Input filtering is of great importance in measurement application with a low level
signal. The effect of low pass filtering is to average out small transients of the
input parameter resulting from process and sensor noise, as well as externally
generated electrical noises. To overcome the sluggish response, associated with
long filter settings, the indicator uses a Selective Filtering technique. This
method allows the transmitter to achieve a fast response for significant variation,
yet to provide a stable, smooth and noise free output.
6.4.1 Damping Factor
The Damping Factor provides a measure of the time (in seconds) over which
the input signal will be averaged. The greater the Damping Factor, the
smoother the output and the slower the measurement display response time.
Selective Filtering implies that Damping is only applied over a limited input
Band around the input levels where noise is most likely to be found. This is the
Filter Band.
6.4.2 Damping Filter Band
The Filter Band is defined as the band (in % of the input span) over which
Damping is applied. A 1% Band for a transmitter with a measurement input span
of 500° C means that Damping will apply to input variations of 0.5° C or less.
However, changes in the input of greater than 0.5° C will be directly reflected in
the indicator’s output without a delay.
Since noise levels do not vary largely between most applications, it is sensible to
assume that wide input spans would require low band settings and narrow spans
would require large band settings. The Configuration software provides for a
calculated optimal filter setting suitable for the majority of applications,
accounting for the specific transmitter input span.
To enable the automatic application of this function, simply click on the “Set to
Optimal”
button. The settings may be changed at any time for
applications where a high level of noise is known to exist, or in a slow responding
system where a very smooth output signal is imperative.