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Might sound silly for many of all but is this device's knob for the current for obtaining constant current or limiting the max current? Can I use this Dc power supply to obtain a constant current regardless of the resisyances? If not what would u prefer as an adjustable current source? Here is the device:
http://electronics123.net/amazon/datasheet/ps613u.pdf

When feeding a DC motor with this the motor spins faster when increasing the current knob. Im a bit confused if it is only for limiting purpose or not.

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It says in the spec you linked that the current adjuster only works on the 0-30V output and can limit from 10mA to 3.2A. I would think that for feeding a current into a resistor this will be OK but don't expect miracle performance, for instance if set to 20mA any resistance higher than 1500 ohm will cause the output voltage to want to go greater than 30V and of course this cannot happen. Also, if you have voltage limit set to 15V, then don't expect the current limit to stay limiting/controlling when the external resistance is above 750 ohms.

EDIT If you are not satisfied with the performance of the power supply and you wanted to try a different method consider this technique: -

enter image description here

With R1 at 312.5 ohms, output current should be 4 mA plus a little bit from the adjust pin (maybe 50 uA). For 20 mA, R1 needs to be 62.5 ohms

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  • \$\begingroup\$ what can I use for a very stable and adjustable accurate current regulation especially between 4 to 20 mAmps? \$\endgroup\$
    – user16307
    Nov 6, 2013 at 15:24
  • \$\begingroup\$ @user16307 - see amendments \$\endgroup\$
    – Andy aka
    Nov 6, 2013 at 15:31
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    \$\begingroup\$ Be aware that this circuit is also not miraculous. If Vin is 10 V (for example) it won't be able to supply more than about 7 V to the load. \$\endgroup\$
    – The Photon
    Nov 6, 2013 at 18:15
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Yes, you can use it exactly as a constant current source (within its limits). You set the Voltage to a maximum (with the knob - be careful that it can go to a maximum) and Current to a minimum (same warning) and then hook up the circuit and ramp up the current limit until you hit the value you want. If the power supply is wired correctly the voltage displayed will be the voltage across the load, from which you can measure the load value.

An Ideal current source will change it's output voltage to conform to the requirements of the external circuit and will develop sufficient voltage to ensure that the current is constant. Up until the point that it can't. Like for example running unto the upper rail. You can't put out a voltage that is higher than what the Power supply itself can supply (but this may be higher than what the power supply puts out when in voltage mode).

You will need to monitor the meters to make sure that it makes sense (not at the limits of voltage ranges) and regulation and control can be marginal at the minimums.

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  • \$\begingroup\$ No, you set the voltage to maximum if you want constant current behavior. \$\endgroup\$ Nov 6, 2013 at 16:11

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