LEM current transducer 2.5 V internal reference

Question

I am testing a LEM LTSR-25-NP current transducer. According to the datasheet, the current transducer should be outputting 2.5 V +/- 0.025 V when the input current is 0 A, but this is not what I am experiencing.

It seems that every time I set up the current transducer using a breadboard, jumper cables, an STM32 MCU, and thd necessary power supplies, I get a different output voltage at 0 A. I got output voltage ranging from 2.6 V all the way up to 3.2 V.

I have also noticed that by moving the jumper cables that are near the transducer, the output voltage changes.

Yesterday I decided to ground the reference pin for a second and see what happens and it actually managed to fix the issue; the output was exactly 2.5 V, but today I tried it again and it doesn't work.

Does anybody have an idea of what may be going on here?

Answer 1

The LTS, LTSR, LTSP Series are intended to be mounted on the printed wiring board of the end-use equipment (with a minimum CTI of 100)

From: https://www.lem.com/sites/default/files/products_datasheets/ltsr_25-np.pdf

These transducers use a current transformer to read the current, changes in the magnetic field next to the device could change the measurement of the device. In addition the device needs to be mounted on a PCB for best results. I would make a PCB for it and keep it away from other wires and components.

Breadboards are also notoriously bad for signals, because of parasitic capacitance and contact resistance.