LEM hall effect current sensing connections

Hi

I am new to electronics and cannot work out how to connect my three pieces together.
I have a LEM Hais 50-P current sensor to be connected to two inverting amplifiers and then to my converter.
The idea is to take the output voltage from the current sensor and amplify it to a range suitable for the converter which will be preferably 0-10V.
The problem is i have no idea how the reference voltage works and what it is to be connected to and texts i have read confuse me more.
Attached is the data sheet for the current sensor and a simple sketch of the three pieces to be connected.
Please, any advice will help
The pieces are for a data logging setup and i cannot understand what voltage i will get out of the current sensor for a corresponding current.

Thanks

First you should understand LEM sensor in order to design interface for it. Data sheet states that unit has reference 2.5V that can be over driven by external low impedance reference if needed. I don't think you need that. Sensor measures both positive and negative currents and output swings to Vref±0.625*Ip/Ipn. Ip is actual current measured and Ipn is nominal RMS current range of your sensor, which in your case is 50A.
You can look at it as if sensor is powered by ±2.5V and Vref is 0V. So, voltage between Vout and Vref will be your actual output that will be equal to ±0.625*Ip/Ipn
Range that your sensor is capable of measuring is ±150A. Accuracy specifications are stated for values up to 50A and is likely that they degraded above that. So next question is what is your current range that you wish to measure? This will determine gain of your amplifiers to achieve 0-10V range. Next you have to determine what your 0-10V range represents? Is it only positive current or negative current, or something else? What is that you are interested to measure? Peak value, absolute value, RMS,... Explain what 0V is representing and what 10V is representing on output?

I use these sensors mainly with a DMM connected between
the output and the reference. I suggest you look at either
an instrumentation amplifier or a fully differential amplifier,
depending on whether your ADC is differential-in or single
ended, ground referred. There are some intrumentation
amps that have multiple gain settings you access by pin
strapping or signal - which could be used to autorange.

Thanks for the reply

The current range thats going to be measured wouldnt exceed 10A...Im going to use them to measure current over time on motor circuit. so it will be used to measure ac.
Is it that i must find what 1A will represent as a voltage?
I would like 0V to represent 0A if that is possible? I thinks its more the understanding of what output voltage i will get from the sensor when a current is passed through it thats confusing me and how it is put together.
Can Vref from the sensor be connected to R3 on the first amplifier and manipulated to cancel it out?

Thanks again

Yes, connecting R3 to Vref and R6 to Vout would give zero output volatge with zero current (if R1 is connected to ground and the resistor values are selected according to the text book). This would however require dual supply for the OP to reproduce values around zero correctly.

Hi again

I still cant seem to grasp this basic electronic setup
I have attached a drawing showing how i connected the circuit up but do not know where to place the Vref connection

The output from the hall sensor with no Ip or input current can be seen from the data sheets.

What should the output from the amplifier be approximatly? And where to connect Vref?

Thanks

To convert the sensor output to a ground referenced bipolar signal, as suggested by the dual supply of your circuit, you would want to use a differential amplifier configuration. The simple single OP, four resistor circuit will do. In this case, the reference terminal would be used as an output. The resistors in your circuit are unreasonable low values, I would choose at least factor 10 higher.

Hi guys,

My application is sensing of charging and discharging of battery and giving the hall sensor output to controller which senses only positive voltages. so i need to level shift the output voltage of hall sensor. hall sensor used is LA55-P.

Anyone please give me the circuit for interfacing hall sensor voltage and controller. also do we need an isolated supply +/- 12v supply for this application.

Go through my attachment also.

--Om

You can e.g. use a LEM HAIS-50, as mentioned above, that connects seemlessly to a 5V processor.

Hi ,
Thanks for the reply.
Are you saying that the circuit attached gives the level shifted voltage output to controller?

Are you saying that the circuit attached gives the level shifted voltage output to controller?

Click to expand...

I'm saying, HAIS55 can connect to a controller without an additional amplifier. With LA55, you need a bipolar supply, a shunt resistor, and a level shift circuit.

Oh thats great..thank you very much for your support.
by the way, which type of industry you are working.

Om

---------- Post added at 16:54 ---------- Previous post was at 16:53 ----------

Hi
Thanks for the reply. But what about the price difference of both.

But what about the price difference of both.

Click to expand...

As far as I know, the single supply, voltage output sensors like HAIS or HTFS are considerably lower priced than the classical dual supply, current output sensors. The absolute measurement accuracy is somewhat lower, but still better than a 10-Bit ADC provides.

Hi ,
I have one more query.
Do we need isolated +/- 12V power supply for LA-55P.

Thanks