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8March2012/version 7

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

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CASR series

1 2 3

10 9 8

Filtering and decoupling

Supply voltage V

C

The fluxgate oscillator draws current pulses of up to 30 mA at

a rate of ca. 900 kHz. Significant 900 kHz voltage ripple on

V

frequencies the power supply rejection ratio is low, and the

ripple may appear on the transducer output

V

V

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

to provide local decoupling (100 nF or more, located close to

the transducer)

Output V

OUT

The output

V

typically 2 Ohms; it can drive 100 pF directly. Adding series

Rf = 100 Ohms allows much larger capacitive loads. Empirical

evaluation may be necessary to obtain optimum results.

The minimum load resistance on

V

Total Primary Resistance

In the following table, examples of primary resistance

according to the number of primary turns.

Reference V

REF

Ripple present on the reference output can be filtered with a

low value of capacitance because of the internal 680 Ohm

series resistance. The maximum filter capacitance value is

1 µF.Application information

Application information

Number of

primary turns

Primary

resistance

R

Recommended

connections

1

0.24

10

9

8

OUT

IN

1

2

3

2

1.08

10

9

8

OUT

IN

1

2

3

3

2.16

10

9

8

OUT

IN

1

2

3