Constant current source
Constant current source
(OP)
I wish to supply hall probes with a constant current. Could be 1 mA or 100 mA. Wish to make sure the hall voltage isn't affected by changes in internal resistance due to temperature. Could make up a current source with op-amp but I don't wish to have to do electronic design or build as I am a mechanical engineer and will probably get it wrong. Are there any products out there ready made to do the job? I have found some expensive programmable supplies for lab applications but this is over kill. Supply voltage 6-12V dc.





RE: Constant current source
RE: Constant current source
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RE: Constant current source
RE: Constant current source
http://en.wikipedia.org/wiki/Current_mirror
The current mirror will give you constant current of any value set by the "so called programming resistor".
RE: Constant current source
http://en.wikipedia.org/wiki/Current_source
RE: Constant current source
RE: Constant current source
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RE: Constant current source
For 1 to 10 mA, the LM334 can be set with a single resistor as a current source. Add a couple more components and get some temperature compensation. Go to www.national.com and search LM334 for datasheet with examples.
For 10 mA to 100 mA, a LM317 type voltage regulator can be setup with a single resistor to act as a current source. Go to www.national.com and search for application note AN-178. Many other three-terminal voltage regulators will act like a current source if connected as descirbed in this note.
There are current source diodes - a single two-lead component that will act like a current source. A little more expensive and somewhat harder to find. According to the book "Current Sources and Voltage Regulators" by Harrison there is a CIL series of current source diodes made by Crystalonics with values from 5.1 to 51 mA. To get 100 mA, put two 51mA devices in parallel (OK, it's actually 102 mA then). The book mentions other manufacturers such as Central Semiconductor, InterFET, Linear Integrated, Solitron, Vishay, but most of their current source diode offerings have a max of around 2 to 5 mA.
Of course the book referenced has plenty of more complex designs with higher accuracy and stability, but these require more components.
RE: Constant current source
RE: Constant current source
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RE: Constant current source
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RE: Constant current source
RE: Constant current source
RE: Constant current source
Whomever you're talking to at Keithley is a nitwit. The 236 is a SOURCE/MEASUREMENT unit and is designed specifically for Hall, Vander Pauw, other similar Kelvin measurements. It can your specific measurement as a standalone system: http://www.keithley.com/data?asset=5512
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