Copley amplifier parameter dictionary - Maccon.de

CHAPTER
3: FILTER COEFFICIENTS
There are several amplifier parameters which are used to define filters. These filters are implemented as generic biquadratic filter structures.
Filters of this type implement the following formula to transform the input parameter x(n) at time n to an output parameter y(n):
y(n) = b0·x(n) + b1·x(n-1) + b2·x(n-2) + a1·y(n-1) + a2·y(n-2)
The values a1, a2, b0, b1, b2 are constants known as filter coefficients. They define the type of filter being implemented.
The values passed to these amplifier filter parameters are used to define the filter coefficients. The formatting of these parameters varies
depending on the amplifier family being interfaced to.
All first generation Copley amplifiers use 16-bit integer math to implement their filters internally. Filter coefficients are given as 16-bit signed
integer values. To increase the resolution of these coefficients, an additional unsigned scaling coefficient (k) is also specified. The actual
filter formula used within these amplifiers is as follows:
y(n) = K · (b0·x(n) + b1·x(n-1) + b2·x(n-2) + a1·y(n-1) + a2·y(n-2)) / 32768 / 4096
To set the filter coefficients on amplifiers of this category, 9 words of parameter data are passed. The first three words of data are
informational parameters which are used by the CME software to describe the filter. If the upper 3 bits of the first word are all set then the
filter will be disabled. Other than that, the first three words of data are not used in any way by the firmware. These three words are reserved
for CME use.
Word Description
1 Filter info. Set to 0xFFFF to disable the filter. Otherwise, reserved for CME use.
2 Filter info. Reserved for CME use.
3 Filter info. Reserved for CME use.
4 b2 coefficient.
5 b1 coefficient.
6 b0 coefficient.
7 a2 coefficient.
8 a1 coefficient.
9 K scaler.
Copley Controls Page 65