DL205 Analog Manual, 7th Edition Rev. D
14-6
Chapter 14: F2-4AD2DA, 4-Ch. In / 2-Ch. Out Analog Combination
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B
C
D
The DL205 base has a switching type power supply. As a result of switching noise, ±3–5
counts of instability may be noticed in the analog input data if the base power supply is used.
If this is unacceptable, try one of the following:
• 1. Use a separate linear power supply.
• 2. Connect the 24VDC common to the frame ground, which is the screw terminal marked “G”
on the base.
When using these methods, the input stability is rated at ±1 count.
Current Loop Transmitter Impedance
Standard 4–20 mA transmitters and transducers can operate from a wide variety of power
supplies. Not all transmitters are alike and the manufacturers often specify a minimum loop
or load resistance that must be used with the transmitter.
The F2-4AD2DA provides 250 ohm resistance for each input channel. If the transmitter
being used requires a load resistance below 250 ohms, adjustments do not have to be made.
However, if the transmitter requires a load resistance higher than 250 ohms, add a resistor in
series with the module.
Consider the following example for a transmitter being operated from a 30VDC supply with
a recommended load resistance of 750 ohms. Since the module has a 250 ohm resistor, add
an additional resistor.
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A
b
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0V
+30V
DC Supply
Two-wire Transmitter
+--
R= Tr −Mr
R--resis tortoadd
Tr -- Transmitter totalresistancerequirement
Mr -- Moduleresistance(internal 250 ohms)
R= 750 −250
R≥ 500
Module Channel 1
R
250 ohms
IN--
IN1+
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