Page 8/12

www.lem.com

070213/7

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

The schematic used to measure all electrical parameters is:

(C

Figure 17 : standard characterization schematics

Ampere-turns and amperes

The LAX transducer is sensitive to the primary current linkage

Θ

Θ

(At)

With N

depending on the connection of the primary jumpers)

Warning : As most LAX user will use it with only one single

primary turn (N

primary currents instead of current linkages. The unit is kept as

ampere-turn (At) to make clear that ampere-turns are meant.

Transducer simplified model

The static model of the transducer at temperature T

I

+ error

In which

error = I

ε

ε

With :

Θ

Please read above warning.

Θ

Pmaxi

: the maxi input ampere-turns that have

been applied to the transducer (At)

I

S

: the secondary current (A)

T

A

: the ambient temperature (°C)

I

OE

: the electrical offset current (A)

I

: the temperature variation of I

O

at

temperature T

G

: the sensitivity of the transducer (A/At)

ε

G

: the sensitivity error

ε

This model is valid for primary ampere-turns

Θ

-

Θ

At zero input current, the model for the offset is reduced to:

I

In which I

maximum input ampere-turns that have been applied to the

transducer.

Sensitivity and linearity

To measure sensitivity and linearity, the primary current (DC) is

cycled from 0 to I

10 steps).

The sensitivity G is defined as the slope of the linear regression

line for a cycle between ± I

The linearity error

ε

the maximum positive or negative

difference between the measured points and the linear regression

line, expressed in % of the maximum measured value.

Magnetic offset

The magnetic offset current I

on the primary side ("memory effect" of the transducer's ferro-

magnetic parts). It is included in the linearity figure but can be

measured individually.

It is measured using the following primary current cycle.

I

Figure 18: current cycle used to measure magnetic and

electrical offset (transducer supplied)

0 V

+

-

M

0 A

t

t

Ip(3)

2

)

(

)

(

2

1

t

Is

t

Is

OM

I

−

=

Performance parameters definition

LAX series 16-100 A