AMETEK DLM 600W Series - Manual (Page 35)

DLM 600W Series
M362161-01 Rev J 2-11
2.9.3 Noise and Impedance Effects
To minimize noise pickup or radiation from load circuits, load wires and remote sense
wires should be twisted–pair with minimum lead length. Shielding of the sense leads
may be necessary in high noise environments. Even if noise is not a concern, the load
and remote sense wires should be twisted–pairs to reduce coupling between them,
which could impact the stability of the power supply. If connectors are utilized for the
power and sense leads, be careful not to introduce coupling between the leads. Ensure
that the connector terminals for the sense leads are in adjacent locations, and minimize
the physical loop area of the untwisted portions. Ideally, the sense leads should be
separated from the power leads and should have their own connector.
Twisting the load wires provides an additional benefit in reducing the parasitic
inductance of the cable. This improves the dynamic response characteristics at the
load by maintaining a low source impedance at high frequencies. Also, with long load
wires, the resultant inductance and resistance could produce high frequency voltage
spikes at the load because of current variations in the load itself. The impedance
introduced between the output of the power supply and the load could make the
ripple/noise at the load worse than the specifications of the power supply (which are
valid when measured at the rear panel bus bars). Additional filtering with bypass
capacitors at the load terminals may be required to bypass the high frequency load
currents.
In addition, when operating with external sense, the recommendation is that it be done
with twisted shielded pair, with one end of the shielding connected to the ground stud
next to the sense connector. The other end does not need to be connected.
2.10 Load Voltage Sensing
Two methods are available for sensing the load voltage: local and remote sensing.
Local sensing measures the voltage internal to the supply at the output terminals.
Remote sensing allows the point of measurement to be relocated to the load.
2.10.1 Local Sensing
Local sensing is the default factory setting, and results in sensing the output voltage
internally at the rear panel output terminals. To select this method of sensing, ensure
that REM SNS of the SETUP switch, Position-1, is set to OFF. Refer to Figure 4-1.