isolated power supplies

[jtm]

I'm looking for an isolated 5V power supply and I don't see many available.
(my application involves thermocouples)

Are all "medical" supplies isolated? I saw one at Jameco (Mean Well
MPS-30-5) that is listed as isolated but I checked the spec sheet and
isolation wasn't even mentioned. The exact same thing with another
"isolated" supply at Jameco: Phihong PSA15LN3-050, the specs say nothing of
isolation.

what am I missing?
jtm

 

[Johnboy]

Isolated usually means that the bobbin has 2 sections,
one for the mains and the other for the low voltage. If the
mains or the secondary short out, there will be no transfer
of voltage to the other winding. Most metal canned xformers
are compound wound with the primary wound first and then
overlaid with the low voltage winding. Fish paper is between
the windings but not always between each wind layer. I might
be way off base with my explanation, but this is what I see
when I have taken xformers apart to assay failures.

 

[Art]

You actually could use a PC power supply with proper terminations to supply
the isplated +5VDC source. They have available outputs of both 12VDC, 5VDC
and many also have 3.3VDC taps. May be an inexpensive source for a isolated,
regulated source for your tests.

 

[Jan-Erik Söderholm]

You actually could use a PC power supply with proper terminations to supply
the isplated +5VDC source. They have available outputs of both 12VDC, 5VDC
and many also have 3.3VDC taps. May be an inexpensive source for a isolated,
regulated source for your tests.

Hi.
I have read somwhare that standard run-of-the-mill PC
PSU's doesn'r work very well if not loaded properly.

Jan-Erik.

 

[jtm]

That will be a problem...I'll be loading from a few mA up to an amp or two.
I eventually want to go to production so I'll need a cheap compact unit.

Since isolation isn't even mentioned in the spec sheets I (a relative
newbie) figured I'm missing 'something' about isolated supplies.

jtm

 

[legg]

I'm looking for an isolated 5V power supply and I don't see many available.
(my application involves thermocouples)

Are all "medical" supplies isolated? I saw one at Jameco (Mean Well
MPS-30-5) that is listed as isolated but I checked the spec sheet and
isolation wasn't even mentioned. The exact same thing with another
"isolated" supply at Jameco: Phihong PSA15LN3-050, the specs say nothing of
isolation.

In the spec,

http://www.phihong.com/assets/pdf/PSA15LN.pdf

the line; "Dielectric Withstand (Hipot) Input to Output 3000VAC, 1
min., 10mA" indicates isolation test limits.

The isolation requirements of the labelled safety standards are what
the product is designed to comply to.

RL

 

[Art]

Strange, seems that I did mention the PC supply being terminated properly,
presuming you would understand that is indicative of proper loading of the
item to regulate and operate correctly. But you apparently love a chase so
go for it, I'm confident that you will find a commercially developed 5VDC
regulated and isolated supply eventually, and pay a fair price for it.<

 

[Eric Smith]

I'm looking for an isolated 5V power supply and I don't see many available.
(my application involves thermocouples)

Are all "medical" supplies isolated?

Any AC-mains-input DC-output power supply you would buy from normal
sources, switching or linear, is isolated. However, there is still some
leakage current. Medical supplies have a lower maximum leakage current
specification.