Teledyne LeCroy WaveExpert 100H Operators Manual - Manual (Page 262)

Operator’s Manual
260
WE-OM-E Rev A
Exponential Decay Time Constant Excel Parameter (Excel Example 1)
This example calculates the time constant of an exponentially falling pulse, such as the light output
of a phosphor.
The first figure shows a typical pulse, including pseudo-random noise, generated by a VBScript.
The pulse was generated by a formula of the form e (1 – t/TC1) * e -t/TC2 , where TC1 and TC2 are time
constants, The requirement is to measure the time constant TC2, using the portion of the trace
where TC1 has negligible effect. This was done using Function F1, which is not a part of the
measurement process.
For the actual measurement, Parameter P1 was set up as an Excel call. In Excel, the selected
portion of the trace was converted to logarithms, and the Excel function SLOPE was used, as
shown here: