R/C Networks

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Synthesizing R/C Networks

ParSer is a utility to construct a non-standard resistance or capacitance value from a set of standard resistors or capacitors. It may be configured to calculate resistors, capacitors or resistive networks by selecting the "Component" as shown below:

ParSer supports different topologies of up to three individual components. The supported network topologies change with the selected component. Select at least one topolgy which shall be analyzed when the search is started.

Before starting the search, a set of available resistors or capacitors must be specified (see Selecting a set). It is possible to select one or multiple sets of standard IEC values or to import a private list.

Finally specify the desired target resistance or capacity, the maximum permitted error and the deviation of individual components. Press the Start button when finished and wait until the results are displayed. Two examples are shown below.

The first example shows how to synthesize a 50 ohm resistor, the second one shows how to synthesize a 50 pF capacitor. The maximum permitted error is 1% in each case. That means that combinations with a larger error than that, are discarded and not displayed in the result window. Note that the precision of the individual components is not considered. They are treated as precise, i.e. their error is assumed to be 0%.

The maximum deviation specifies, how different the individual components may be. It is often not useful to combine components with vastly different properties. The maximum deviation is the maximum factor by which the individual components may differ. Selecting a smaller maximum deviation will help to keep the runtime short. It will exclude many values from the full calculation as they are sorted out early.

ParSer uses brute force to find suitable components, since there is no analytic formula to calculate them. That means that ParSer calculates the result for each combination of individual values and this calculation is done with double precision floating point numbers. The execution time is directly proportional to the number of computations, but the number of computations depends exponentially on the number of selected topologies and the number of entries in the selected IEC table. Therefore calculation can take very long if worst case conditions are selected. Consider to reduce ParSer's processing priority to "idle" by the -$pt=0 command line parameter, so that it can run in the background without too much impact on system agility. During the search, one can also press the suspend button to temporarily release the CPU from its burden.

Note that suffixes may be appended to the specifies values. The following suffixes are supported:

T: *1e12

G: *1e9

M: *1e6

k: *1e3

m: *1e-3

u: *1e-6

µ: *1e-6

n: *1e-9

p: *1e-12

%: *1e-2

Any character following the suffix is discarded. That rule permits to specify values like µF or MOhm.

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