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WEBENCH® Tools/LDC1614-Q1: Target material selection

Gabriele Sereni33
Prodigy 10 points
Part Number: LDC1614-Q1
Other Parts Discussed in Thread: LDC1614

Tool/software: WEBENCH® Design Tools

Dear all,

We are developing a position sensor using LDC1614, one of the most strict specifications is the high accuracy level required, thus we are searching for the target material which allows to reach the maximum sensitivity. Following the design notes reported in SNOA957A ("LDC Target Design") we noticed that copper and aluminum show the highest frequency shift as a function of the normalized distance (coil - target). 

The questions are the following:

1)Does someone investigated the effect of additional thermal or thermochemical treatments like tempering and cementation on the electromagnetic characteristics (i.e. conductivity and magnetic permeability)?

2) Is there a comparison in terms of the frequency shift per normalized distance between copper and aluminum and other stainless steels (e.g. the AISI 416 and others)? Where it places compared to the other alloys reported in Fig. 12 (see below).

3)Taking as reference the Fig 13 of the SNOA957A  (reported below), is it correct to consider the frequency range above 2MHz as the correct operating area for AISI 416 SS? 

4) Are the three curves reported in Fig 13 obtained with a target positioned at a fixed distance, varying the sensor frequency ?

5) Since the slope of the SS416 curve is steeper compared to aluminum and copper does it means that the sensitivity is higher 

compared to those obtained with the latter? 

6) Does the steeper characteristic has a detrimental effect on the level of frequency noise (i.e. a variation of the sensor frequency  reflects in a variation of the inductance)? 

7) Which are the best operative point  for the different materials reported?

Thank you in advance  for your cooperation

Regards

Gabriele

  • 0
    TI__Genius 11340 points

    Hi Gabriele,

    Here are our answers to your questions:

    1 and 2. Unfortunately, we do not have the data.

    3. You can operate anywhere along the curve; however, operating at frequencies above 2MHz would give you the best performance.

    4. Correct. We used a fixed distance and varied the LC tank capacitance to obtain different frequency values.

    5. Figure 13 is showing maximum inductance (frequency) shift. Sensitivity is not determined by the slope but rather how far it is from 0%. Either a very large positive shift or a very large negative shift is good. If you are operating at the 0 crossing you would not see inductance shift when you move the metal.

    6. It does not

    7. Higher frequencies allow you to operate in a region where conductivity is more dominant than permeability effects. At a frequency of >5MHz, most metals start to have a smaller and smaller difference.