need help: gear tooth counting

Madhu Rajakrishnan

Prodigy 80 points

can you give the expression of the coil diameter and number of turns which can be used as sensor coil in ldc1000???????

over 11 years ago

0 Ben Kasemsadeh over 11 years ago

TI__Genius 13650 points

Hello Madhu,

please refer to "Q2. What is the min/max inductance or min/max coil diameter which the LDC1000 can drive?" in the FAQ of the inductive sensing forum: http://e2e.ti.com/support/data_converters/inductive-sensing/f/938/t/295036.aspx

0 Evgeny Fomin over 11 years ago

TI__Genius 9300 points

Please also look at automated coil design tool at http://webench.ti.com/webench5/ldc/?lang_chosen=en_US

0 Madhu Rajakrishnan over 11 years ago

Prodigy 80 points

thank you sir for quick reply...I'm currently doing my mini project work on gear tooth counting...instead of using pcb coil im trying to use air core coil...for designning this coil i need the formulae of diameter and no of turns which should be taken such that i may work on different possibilities of coil

0 Madhu Rajakrishnan over 11 years ago in reply to Evgeny Fomin

Prodigy 80 points

sir this gives the direct design of coil in pcb....can you which suggest which one is ideal coil for gear tooth counting...pcb coil 8,18,13 for target diameter of 10cm,,distance between them of 1.5 cm

0 Ben Kasemsadeh over 11 years ago in reply to Madhu Rajakrishnan

TI__Genius 13650 points

Hello Madhu,

for gear tooth counting, there are two rules of thumb to achieve best performance:

To detect the conductive target reliably, the physical size of the inductor should not exceed the size of the target (ie the gear tooth).
The distance from coil to teeth should be less than 50% of the coil diameter.

Therefore, a physically small inductor close to the gear teeth will provide better performance than a large inductor at far distance.

0 Madhu Rajakrishnan over 11 years ago in reply to Ben Kasemsadeh

Prodigy 80 points

hello sir,

thanks for reply,,, noted with thanks.. on what basis you are saying teeth should be less than 50%.. is there any relation or expression....

0 Madhu Rajakrishnan over 11 years ago in reply to Madhu Rajakrishnan

Prodigy 80 points

on what basis you are saying teeth should be less than 50%.. is there any relation or expression....

0 Ben Kasemsadeh over 11 years ago in reply to Madhu Rajakrishnan

TI__Genius 13650 points

The reason is that beyond 50% of the coil diameter, the density of magnetic field lines decreases. This results in a decrease of sensitivity for inductive measurements beyond this point. It is possible to use a larger sensing distance, especially if a ferrite is used, but measurement performance will drop off. Note that the length of the EM field is proportional to the physical size of the coil.

0 Madhu Rajakrishnan over 11 years ago in reply to Ben Kasemsadeh

Prodigy 80 points

hello sir,

thanks for your kind notice of my question and i got my answer.....sir according to principle "there will change in inductance when a metal plates cuts the coil" this is due to magnetic couplings between the metal and coil....having a doubt sir!!!!! Is there any relation between the frequency applied to coil and the eddy current produced in the metal plate?????

thank you sir

0 Evgeny Fomin over 11 years ago in reply to Madhu Rajakrishnan

TI__Genius 9300 points

The LC tank always oscillate at the resonant frequency. Eddy currents will change the inductance of the system, and thus, resonant frequency.

0 Madhu Rajakrishnan over 11 years ago in reply to Evgeny Fomin

Prodigy 80 points

Hello Sir,

I am lucky to get support from you sir...Is that coil should be energized with alternating current sir but ldc1000 is of working with dc supply...can you explain sir????

0 Evgeny Fomin over 11 years ago in reply to Madhu Rajakrishnan

TI__Genius 9300 points

While LDC1000 power supply is indeed DC, it drives the LC tank (snesing coil and a cap) at its native resonant frequency.

0 Madhu Rajakrishnan over 11 years ago in reply to Evgeny Fomin

Prodigy 80 points

hello sir,

In the interfacing of ldc1000 with the msp430g2 launchpad,,,what is the requirement of placing 38.768KHz...can you elaborate in brief manner????

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need help: gear tooth counting