High current Measuring sensor

Dear all,

I am trying to build string monitor for solar application. There are two ways of doing it. The purpose to measure current from various string of panel.

1)hall sensor
2)Dc shunt basis.

I have succeed with hall sensor based,. Now i am trying to build DC shunt basis. Is there any one can share how to build it.
any other way you can suggest me of doing it

each current string of 1000V , 20A . There are totally 25 string,

There are totally 25 strings , 1 temperature, 1 humidity.

You can use HCPL-7520 linear optoisolator in circuit to isolate the high voltage.

http://people.ece.cornell.edu/land/courses/ece4760/FinalProjects/s2008/cj72_xg37/cj72_xg37/index.html

Why would you not want to use a hall sensor which provides a simple and reliable method of accurate current measurement and effective electrical isolation with minimum number of components (ie 1)

AMPS-N:
I have succeed with hall sensor based,.

Job done.

jackrae:
Why would you not want to use a hall sensor which provides a simple and reliable method of accurate current measurement and effective electrical isolation with minimum number of components (ie 1)

Erm, because they are much noisier than a shunt or transformer sensor? Unliklely
to matter for this application.

MarkT:

jackrae:
Why would you not want to use a hall sensor which provides a simple and reliable method of accurate current measurement and effective electrical isolation with minimum number of components (ie 1)

Erm, because they are much noisier than a shunt or transformer sensor? Unliklely
to matter for this application.

On what basis do you make that statement. Transformer unsuitable for DC current sensing so not relevant to the topic

Have you ever used a hall current sensor? Or looked at a datasheet?

ACS712 +/-5A sensor at full bandwidth is about 0.5A noise (input refered).

Their advantages is that they are small and cheap, single SOIC8 package for
some of them, and have a good overload capability (resistive shunts don't
cope with overload well!)

Yes you can use transformer sensors at DC, they work by adding a hall sensor
or magnetoresistive sensor in a gap and providing closed-loop) feedback to
the secondary to keep its signal at zero.

You can use a much more sensitive hall plate so noise is much less (100's of times
less I think). Lots of sensors use this arrangement and have decent performance.
More expensive and very bulky of course.

Perhaps you are confusing a pure hall sensor and a closed-loop current sensor?

Yes I have used hall sensors and in every case they have provided a perfectly adequate measurement system.

The following is extracted from the ASC712 data sheet :

Noise (VNOISE). The product of the linear IC amplifier gain
(mV/G) and the noise floor for the Allegro Hall effect linear IC
(?1 G). The noise floor is derived from the thermal and shot
noise observed in Hall elements. Dividing the noise (mV) by the
sensitivity (mV/A) provides the smallest current that the device is
able to resolve.

For the subject device with a +/- 20A range the output is specified as 100mV/A with a nominal noise figure of 11mV.
From the above sheet this gives a minimum resolution of 11/100 = 110mA. With a 20A range, this gives a possible resolution of just over 0.5% referenced to FSD.

For non-scientific applications I would have thought this was more than adequate.

But it's up to each to use what they wish

Hi,

each current string of 1000V , 20A . There are totally 25 string,

Is that right?

Please a picture of them.
A circuit diagram of how you have connected them, 1000V at 20A = 20,000 Watts and you have 25 of them.
Is that right?

Tom… :slight_smile:

Hi,
Where is “Ground” in this system??

IF you can put the DC shunt type sensor at the ground end, a simple 0.1 ohm resistor will give you 2 volts at 20 amps. Low noise too…

On exploring lot
http://www.ti.com/lit/ml/slyb194a/slyb194a.pdf
Lot i found that using these kind of amplification network. We can drop the voltage from 1000v in Mv range. can Some suggest me how to use network IC.

http://www.ti.com/lit/ml/slyb194a/slyb194a.pdf

This is a very good source of information on measuring current using “Current Shunts”, which are really just low-resistance resistors.

“Standard” current shunts are usually 50 Millivolts (.05V) drop fullscale. High current ones look like this:

I had one of these on my desk at IBM as a paperweight, when we trying to measure picoamps of semiconductor gate leakage

What accuracy do you need? A standard 0.1 ohm resistor may be enough, especially if you can do a calibration with a good digital meter.