Appendices
Noise, Shielding, and Crosstalk Considerations
B
B-3
prevent noise from being coupled into your measurements. Be careful about
the routing of your input wiring: keep it away from or shielded from all ac
power mains wiring and other sources of noise.
3.
Channel Spacing
When possible, leave as many unused channels as possible
between your ac voltage channel inputs and your low level inputs.
Crosstalk from a V ac or frequency signal on a FAI module channel to an
adjacent channel using the slow reading rate is as shown in Table B-1:
Table B-1. FAI Module Crosstalk Specifications.
V ac/Frequency
Volts DC
Resistance
Temperature
(100 Ohm RTD)
Temperature
(Thermocouple)
<100 Hz
-80 dB
.2%/V if R>3k
.04°/V
.1°/V
100 Hz
-100 dB
.1%/V if R>3k
.02°/V
.003°/V
500 Hz
-100 dB
.1%/V if R>3k
.02°/V
.03°/V
1 kHz
-50 dB
.1%/V if R>3k
.02°/V
.3°/V
2 kHz
-60 dB
.05%/V if R>3k
.02°/V
.1°/V
5 kHz
-66 dB
.1%/V if R>3k
.02°/V
.1°/V
10 kHz
-80 dB
.01%/V
.02°/V
.1°/V
20 kHz
-50 dB
.02%/V
.05°/V
.1°/V
50 kHz
-40 dB
.05%/V
.1°/V
.5°/V
100 kHz
-40 dB
.1%/V
.2°/V
1°/V
>100 kHz
-40 dB
.1%/V
.4°/V
2°/V
Note The temperature ranges are particularly susceptible to crosstalk at frequencies above
20 kHz, and that the error goes up as the square of the voltage, e.g., 2 V ac at 100 kHz can
cause a 4 degree error on a thermocouple. Because of this sensitivity, it is not advisable to mix
temperature signals and high frequency signals in the same 2680 Series.
Summary of Contents for 2680A
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