Ac current sensing methods

[Bjtpower]

Hi Techies

Looking for the Isolated and non isolated sensing techniques..??

I want to measure a ac current and provide it to the Controller adc for further calculations.?

Any links or articles pls suggest.

 

[zofz]

non-isolated, from high side? How high voltage?
Sampling ac signal (what frequency range) or for power 50/60Hz rms/peak analog processed and presented to the uC ADC?
For example there are cases where a bulb and photo-resistor or resistor and temp. sensing would do.
There are current sensing transformers too : **broken link removed**

 

[Bjtpower]

Isolation verses Non Isolation

Can anyone tell me what is ISOLATION? why it is necessary.

will the Differencial amplifier (Mainly used for current Measurements ) is isolated or non isolated..??

Too much Confusions in isolated and non isolated..??

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is above circuit is isolated or non isolated..??

I know the little difference of isolated and non isolated where the Grounds are different of each circuit to avoid the Stray current passing through any circuits and to avoid the Electrical damages.

In the above circuit, i am seeing Neutral and GND are not connected anyhow..

pls explain... confused.

 

[FvM]

Two circuits are isolated against each other if there's no current path between them.

Clearly the measurement circuit is not isolated from mains. We can also assume that N is earthed at the switchboard or distribution transformer.

The shown circuit doesn't work reliably without a short between and +5V ground, even if the +5V supply itself is isolated and the circuit has no external connections, due to the small common mode range of the differential amplifier.

 

[D.A.(Tony)Stewart]

The problem is Neutral may have up to 5% line voltage on it with line drop which exceeds CM input range.

You could have it connected to line and floating from earth with CM chokes on sense wires and output thru IR isolated UART

 

[schmitt trigger]

Very simple explanation:
A non-isolated circuit has the capability to electrocute you.

If you're unsure of which one to use, then -for your own safety-always use an isolated solution.

 

[D.A.(Tony)Stewart]

Power lines carry environmental transients from lightning which may be common to both line and neutral from induced currents. Typical good consumer products are rated for immunity of 3kV 10us transients.

Therefore optical and transformer isolation is the most common method of isolation to local circuits that may or may not be grounded. Components with these insulation breakdown protection are available for use according to signals or power being transferred.

 

[Bjtpower]

Probably i think the the +5v and gnd is from the Power supply which is already isolated by mean of step down transformers..??

What are the Criteria for the isolations..??
only Galvanic or using Transformer are only two ways to isolate it.

 

[D.A.(Tony)Stewart]

It depends on regional standards, application.

Above or below ground AC power distribution makes a difference for local stress factors.

Lightning frequency in Florida is 240 strokes per minute in a region during peak of a storm , so probability is high.

For commercial /industrial use 6kV protection is optional by design.

AC power meters have arc contacts rated for 6kV or 100kA