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LDC1612: ldc1612 data unstable

daohai wang
Prodigy 70 points
Part Number: LDC1612

Hi Ti, I'm testing LDC1612 and now I found a problem, when the target is in steady state, the output data of LDC1612 is not a straight line. I want to know why and how to improve my design.Help me please~~~

L：Ferrite Magnetic Can(shield)+ PCB coil 

C:1000pF /np0/1%

target : 90mm*90mm steel

distance：1~3mm


config @1mm

config @3mm

Idrive settings

   The target has been stationary, why is the data still rising?

  Action 10μm, sampling 7000 data

@1mm the LC

@3mm the LC

 my test device

  • 0
    TI__Mastermind 18545 points

    Hello, 

    I have a couple follow up questions for you in regards to this issue: 

    • If you continue taking data, does the measurement ever get to a steady state or does it always continue to move? 
    • What is the time frame for the data plot you shared? It says 7000 samples, but is this at the device sample rate or are you saving data at a different rate in the data streaming tab? 
    • Do you have a second test device to test with and if so, does it also show the same data response?

    With the LDC devices, you can get slight data drift over temperature even with the use an np0 grade capacitor. This may be what is happening but taking a look at a longer data set would be helpful in determining this. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    Prodigy 70 points

    hello.

    A1: No,target is still,data will keep move, just like curve(change small but slow),not straight. I'm test many time.

    A2: Long time, maybe 5-10 min

    A3: Yes, I have my PCB board(1 pcs). And same L,same target, same program code settings.

    It's a big problem, last week it's work good(the data like straight), today it's not good.I don't know what's going on, I don't have any clue..

    Power on, register set, then data streaming, the data(uH) starts decline immediately.

  • 0 in reply to Justin Beigel
    Prodigy 70 points

    This is my plan: use my PCB board, put NTC close to L, sample data (uH) by rs485 24h+, I'll see if it's caused by temperature drift, is there any better suggestion for me?

  • 0 in reply to daohai wang
    TI__Mastermind 18545 points

    Hello, 

    Based on the oscilloscope captures you provided, you can also increase the IDRIVE setting to 27 to increase the sensor amplitude when the target is 1mm away from the sensor. 

    I have an additional question for you. Your data is drifting at the 1mm end, but does the same issue occur when the target is 3mm away from the sensor? 

    Thank you, 

    Justin Beigel