Select the current-sensing resistor value so that the power dissipation is minimized while as
much of the GPIC input range as possible is used. The current-sensing resistor value should be
less than or equal to the lesser of the values obtained from the following equations:
R
CSR
_
max
≤
P
CSR
I
in
_
rms
2
R
CSR
_
max
≤
GPIC
range
AI
gain
× I
in
_
max
where
P
CSR
= Current-sensing resistor power (1 W for 2512 footprint, 0.25 W for 1206
footprint).
R
CSR_max
= Maximum resistance of the current-sensing resistor (in Ohms).
I
in_rms
= RMS value of the input current (in Amps).
I
in_max
= Maximum input current (DC or
pk − pk
2
) (in Amps).
GPIC
range
= Input range set for the GPIC (10 V or 5 V).
AI
gain
= Gain of the interface board amplifier (x1, x2, x3, x4).
Note Use the maximum gain for simultaneous sampled analog input to get a lower
power dissipation from the current-sensing resistor.
Table 14. Simultaneous Sampled AI Current-Sensing Resistors
Simultaneous AI 2 W Current-Sensing Resistor 0.25 W Current-Sensing Resistor
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