Page 15/18

11July2018/Version 1

LEM reserves the right to carry out modifications on its transducers, in order to improve them, without prior notice

www.lem.com

LES series

Application information

Filtering and decoupling

Supply voltage U

C

The transducer has internal decoupling capacitors, but in

the case of a power supply with high impedance, it is highly

recommended to provide local decoupling (100 nF or more,

located close to the transducer) as it may reduce disturbance

on transducer output V

out and reference Vref due to high varying

primary current. The transducer power supply rejection ratio is

low at high frequency.

Output V

out

The output V

out has a very low output impedance of typically

1 Ohm; it can drive capacitive loads of up to 100 nF directly.

Adding series resistance Rf of several tenths of Ohms allows

much larger capacitive loads Cf (higher than 1 µF). Empirical

evaluation may be necessary to obtain optimum results. The

minimum load resistance on V

out is 1 kOhm.

Figure 29: filtered V

out connection

Total Primary Resistance

The primary resistance is 0.72 mΩ per conductor.

In the following table, examples of primary resistance according

to the number of primary turns.

Number

of

primary

turns

Primary

Nominal

RMS

current

Output

voltage

V

out

Primary

resistance

R

P [mΩ]

Recommended

connections

1

±

I

P N

2.5 ±0.625

0.24

10

9

8 OUT

IN 1

2

3

2

±

I

P N/2

2.5 ±0.625

1.08

10

9

8 OUT

IN 1

2

3

3

±

I

P N/3

2.5 ±0.625

2.16

10

9

8 OUT

IN 1

2

3