How to configure LEM LA 55-P as a regulator or sensor?

[wqrox]

Hey guys, i need some help on the current transducer LA 55-P. I have been finding examples on it on the net but there was no help at all. I just need to know how to configure it as a regulator or sensor. Is urgent. Thanks.

 

[Mr.Cool]

lem la 55-p

this is a hall effect current sensor. product datasheet found here

**broken link removed**

you supply it with +/- 15V, and you read on the sense wire a proportional current. that current should be directed towards a resistors ("burden" resistor) of ohmage value given in datasheet.

the voltage developed across the resistor (current * resistance) is the proportional voltage which you can use in your circuit easy.

the secondary current, or sense current, has a scaling given in the datasheet. if the primary senses 50 Amps peak, then your secondary sense current is 50/1000 = 0.005Amps peak. when directed to a 100 ohm resistor (of sufficient wattage rating) the voltage is 0.005 * 100 = 0.5V.


Mr.Cool

 

[wqrox]

la 55-p

But regarding the current direction, how do u set the current direction as what u wan? and as a regulator, how do u go about connecting it? sorry, i am new to electronics.

 

[veiledcavalier]

la55-p

HI
I am using the LEM LA 55-P for current sensing
Its conversion ration is 1:1000 i think it means 1(2ry): 1000(1ry) as 1ry nominal current is 50A and 2ry nominal current is 50mA

I am using it now for measuring current in the range of 2A, so if I am using a 68 ohm resistor I will get 0.136V on the Rm. the current I am measuring is low for a lab machine, later on I will turn for the industrial one.

So, How to increase that voltage 0.136V so I can get a good range??
I am thinking of increasing number of turns of the 1ry wire!! ??
Is that true???

Best regards

 

[hakeen]

la 55 p

You cant internally soemthing change to boost M Output value. Moreover, the burden resistors are limited by datasheet specs (60...100Ohm).

You need external circuitry to boost your signal (with sufficient gain). But this will surely result in additional offset/nonlinearity into your circuit. The hall effect sensor component can already have error of 2% considering temperature drift and burden resistor change over temp.

 

[veiledcavalier]

lem la

Thanks for your reply
But I don't mean changing something internally !!
I mean that instead of just passing the 1ry wire inside the hall of the sensor, I can make loops on the core. In other words i want to make turns of the 1ry wire on the upper limb of the LEM 55-p current transducer.

Is this also wrong??
thnx

 

[hakeen]

la 55-p+example

Idea is really good, but I think it is unfrotuntely not possibleto do several loops of wire, as you will definitely disturb the magnetic field causing offsets. Hall effects Components are designed for single wire going through primary hole (you can see notice for single wire in the datasheet remarks).

PS. Several loops of wire might also disturb insulation capabilities of device, but I am not 100% sure.

To me output amplfication seems the only way. Or you can use use something like HCPL-7510 or 7800 etc. They are isolation amplifiers with additonal gain. So the signal is ready to be fed to uC.

Cheers