Fluke 2635A, User Manual

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B-1
Appendix B
Crosstalk Considerations
Introduction
This appendix augments the discussion of ac signal effects on other channels (crosstalk).
Effects on each measurement function are discussed below. These numbers should only
be considered as references. Since cross talk can be introduced into a measurement
system in many places, each setup must be considered individually.
The effect of cross talk could be much better than shown for "Typical"; in extreme cases,
the effect could be worse than the "Worst Case" numbers. In general, the "Worst Case"
information assumes that none of the guidelines for minimizing cross talk (Chapter 1)
have been followed; the "Typical" information assumes that the guidelines have been
followed where reasonable.
These numbers assume that input L (low) is tied to earth ground; refer to "Using
Shielded Wiring" in Chapter 1. For dc volts and thermocouple temperature
measurements, a source impedance of 1 k
e
in series with the H (high) input is assumed
(except where otherwise noted.)
AC Signal Cross Talk in a DC Voltage Channel
DCV Error Ratio (CTRR) =
VDC error
VACrms
( )

 

Worst case Typical
50, 60 Hz, ±0.1%: 1.1
×
10
-7
2.0
×
10
-8
Other Frequencies: 3.8
×
10
-6
8.6
×
10
-7
For example, the typical effect on a channel measuring dc volts (300 mV range) by a 300
V ac signal at 60 Hz on another channel would be: 300
×
2.0
×
10
-8
= 0.01 mV.