AC current measurment problem using LTS 25-NP Current Sensor

[anoman]

I use LTS 25-NP current sensor to measure ac current grid. I just built it. I tried to calibrate it using simple circuit consists of a single phase source and high power resistor. The current is flowing when I change the source voltage as appearing in the Ammeter but the output voltage from the sensor still 2.5 V ( 2.5 V means zero current flowing). The current sensor is then connected to a simple DC circuit to check it. The sensors worked accurately. I didn't know what is the problem with measuring AC current using this sensor.
Can you please help me.

 

[schmitt trigger]

A couple of things first:
-LTS 25-NP datasheet
-Your schematic, exactly as you built the unit.

 

[KlausST]

Hi,

the output is still AC, but biased by 2.5V DC.
This means if you connect a DVM to the output you will see 2.5V regardless of AC current.

Use a scope and see the waveform.

To see the current with a DVM you need to rectify and average the AC part or do some RMS calculations.

Klaus

 

[anoman]

Data sheet: **broken link removed**
schematic:

 

[schmitt trigger]

Your circuit is wired correctly. And as Klaus mentions, if your DMM is set in the DC range, you will only read the average voltage of the sinusoid, which still is 2.5 volt.

What you need to do, if you don't have a oscilloscope, is to add a 0.01uf capacitor in series with the output, and read it with your DMM set to AC VOLTAGE.

If you don't have a 0.01 uF, you can use a 0.1 uF, but because a DMM's impedance is 10 Meg, the output will take many seconds to settle.