Tektronix CSA8000B User Manual
Page 178
Creating Math Waveforms
3- 104
CSA8000B & TDS8000B User Manual
Source Dependencies. In general, math waveforms that include sources as
operands are affected by updates to those sources:
H Shifts in amplitude or DC level of input sources that cause the source to clip
also clip the waveform data supplied to the math waveform.
H Changes to the vertical offset setting for a channel source that clip its data
also clip the waveform data supplied to the math waveform.
H Changes to the acquisition mode globally affects all input channel sources,
thereby modifying any math waveforms using them. For example, with the
acquisition mode set to Envelope, a C1 + C2 math waveform will receive
enveloped channel 1 and channel 2 data and, therefore, will also be an
envelope waveform.
H Clearing the data in a waveform source causes a baseline (zero-volt level) to
be delivered to any math waveform that includes that source until the source
receives new data.
Time Base Dependencies. Selections for math-waveform sources (operands)
consist of channel and reference waveforms that are acquired or defined and
viewed in the main time base.
The math waveforms derive their time base and record lengths from waveform
sources. You cannot change them directly; you can only change them indirectly
by changing the time base for the source.
In case of sources having different record lengths, the math waveform created
matches the shorter waveform, and the additional trailing data from the longer
waveform is not used.
You may also want to read the section about deskewing channels on page 3--96.
Expression Syntax. You build math waveforms using the Define Math Waveform
dialog box. To help you create valid math waveforms, this dialog box blocks
illegal entries by disabling any dialog-box element that would create an invalid
entry in the math waveform expression.
The syntax that follows describes valid math expressions, which can be quite
complex (in excess of 100 characters long):
<Expression> := <UnaryExpression> | <BinaryExpression>
<UnaryExpression> := <UnaryOperator> ( <Term> )
| <UnaryOperator> ( <Expression> )
<BinaryExpression> := <Term> <BinaryOperator> <Term>
| <Scalar> <BinaryOperator> <Term>
| <Term> <BinaryOperator> <Scalar>