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There are temperature sensors which are powered the following expensive supply: http://www.prelectronics.com/pdf/2222-2476-US.pdf Here it is mentioned: "The power supply is based on primary switchmode technology to achieve a high efficiency." and "Galvanic isolation between the primary and the secondary voltage is achieved through the double-isolated safety transformer."

I need to install a new system with new sensors and need a new power supply. I found a cheaper power supply which has the data-sheet: http://docs-europe.electrocomponents.com/webdocs/0802/0900766b808023f1.pdf

Someone used the first power supply model I linked and I don't know if there was a specific reason for that power supply. I'm guessing for transducers like temperature sensors the isolation, ripple voltage ect. might be important.

I have couple of questions:

1-) Is the cheaper power supply I found(second link) an SMPS? Because it is not mentioned.

2-) And again in the second power supply the Isolation resistance > 5MOhm. Does that mean there is good galvanic isolation?

3-) Would it be okay to use the cheaper one instead of the first one?

I'm asking because I'm wondering if there is something special about the first power supply(first link).

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1) The second power supply has to be SMPS, deducing from the size, efficiency and auto-select AC input.

2) The second power supply is also double/reinforced insulated meeting relevant safety standards.

3) Don't see anything special about the first one. With a quick glance, the spec of the second one is better. Example: Second one - 50mVpp ripple vs. first one - 40mVRMS (translate to either 70mVpp or 140mVpp, I am not sure).

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Below are answers:

1.) Second Linked datasheet mentions : "Switching frequency 175kHz to 225kHz at input voltage dependent 24V, 2.5A 100kHz to 130kHz input voltage dependent 24V, 5A So yes it is an smps

2.)I think Galvanic isolation is design technique of how you interface the temprature sensor to other components. Now Signals can pass between galvanically isolated circuits, but stray currents, such as differences in ground potential or currents induced by AC power, are blocked. So i think for temprature sensor as you mentioned 5M ohm is fair enough.

3.) Yes its perfectly fine to use second one, i am assuming you have checked the overall power calculation and is in range.

Do let me know for any specific query.

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  • \$\begingroup\$ Im not sure whether your Galvanic isolation understanding is true. I thought it is isolation between input power lines and output power lines.. \$\endgroup\$ – user16307 Apr 20 '16 at 7:43

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