CCS: MSP430FR5887 Non-magnetic sensor

Hello,

I'll need to check with our ESI team and get back to you. The recent holidays may delay their response, so we appreciate your patience.

In the meantime, please check that the ESI2 errata is not causing this behavior. Also, when you mention the consistency of the inductance value, are there multiple sensors in the same system or are the inductor variations across each system? What's the expected variation?

Also, Section 37.2.1.7 Optional Comparator Offset Cancellation in the MSP430FR58xx, MSP430FR59xx, and MSP430FR6xx Family User's Guide mentions the following:

The ESI's comparator has an offset that drifts over temperature and supply voltage. For some applications the specified offset error and offset drift may be acceptable - see device-specific data sheet. If the offset error is not acceptable, adding a comparator autozero cycle within the TSM sequence can minimize the offset error. After the inserted autozero TSM cycle, the comparator operates effectively with a zeroed offset.

I suspect that this has something to do with the count loss as the temperature increases.

Regards,

James

hello,

        I'm glad to hear from you,Here's the situation.The sensor has three inductors, each of which will have a different value. If the difference is large (10uH), the high temperature count will be inaccurate.You said ESI2 errata I saw is the possibility, but where can I download the device - specific data shee, and Optional Comparator Offset Cancellation sample program

Hello,

Would you be able to share your schematics? If so, please don't post them here in case they are proprietary but instead, request my friendship and after I accept, you'll be able to send them to me privately. Our ESI team will be available on Thursday, so the schematic will help them in this investigation.

Thanks,

James

I don't know why, my email can't go out

hello,

     When will you know the result.I'm in a hurry here.

thanks

Hello,

I'm sorry about the delay. I will ping that team for an update and let you know early next week.

Regards,

James

Hello,Johann

    Sorry I'm late. It's Chinese New Year.

    I'll try it your way.               

    mine has 160...(Do you have 160 laps of inductance?) Have you sent any photos to see？ how many uH? Mine is 470uH and 220pF)

Hello,Johann

     Can you provide a brand and model of inductance that you think is ok, so that we can continue the experiment.

thanks

Hi,

I cannot propose a specific brand, but I can explain how I would select a coil that is suitable.

The inductance of a coil is influences by the # of turns and the AL-value of the core. The equation is : L=AL*n^2.

n are the # of turns ; AL is usually given in nHy. it is determines by the for of the core and the the material property "u_r".

The "u_r"-value of the core influences how the magnetic field is formed by the coil; it also influences the inductance as shown above.

As you can see above high "u_r" ties the fiels into the core. But we do not want this because wee need an external field to sense the presence of an metal.

Therefore a coil with low "AL" id better.

If you have a coil with 160 turns to get to 470uHy  => "AL"=470u/160^2=18.35nHy.

A coil that only has 50 turns has an "AL" of 188nHy  => here the first coil is better since a larger external field can be expected.

The other way to test is is simulating the geometry of simply measuring it. Here the "Dip-Meter" is helpful. You can see the impact of the "Dip" in dependency of the distance of the tans circuit.

Hi,

I cannot propose a specific brand, but I can explain how I would select a coil that is suitable.

The inductance of a coil is influences by the # of turns and the AL-value of the core. The equation is : L=AL*n^2.

n are the # of turns ; AL is usually given in nHy. it is determines by the for of the core and the the material property "u_r".

The "u_r"-value of the core influences how the magnetic field is formed by the coil; it also influences the inductance as shown above.

As you can see above high "u_r" ties the fiels into the core. But we do not want this because wee need an external field to sense the presence of an metal.

Therefore a coil with low "AL" id better.

If you have a coil with 160 turns to get to 470uHy  => "AL"=470u/160^2=18.35nHy.

A coil that only has 50 turns has an "AL" of 188nHy  => here the first coil is better since a larger external field can be expected.

The other way to test is is simulating the geometry of simply measuring it. Here the "Dip-Meter" is helpful. You can see the impact of the "Dip" in dependency of the distance of the tans circuit.

So it seems that the current inductive material used is no problem.Should I change the circuit? My circuit looks like figure 1-3, ESIVDCC=3V.I want him to use it for 16 years. Should I change it to figure 1-6?Should I change the parameters of LC?

Can you say what state the inductance of the sensor should be in when these three functions are run?for example :1.2. The sensor is placed on the 180-degree metalpointer of the water meter, and the pointer does not rotate;3. The sensor is placed on the 180-degree metal pointer of the water meter and the pointer turns;Or some other state.

TMS_Auto_cal ();

Find_Noise_level ();

Set_DAC ();

I saw that in SLAA639, but I didn't quite get it.

TMS_Auto_cal ();It doesn't say what state it's running in.

Find_Noise_level ();What is the state of the inductance when the pointer is not moving?1. One of the inductors is above the metal and the other two are above the nonmetal;2. One of them is above the non-metal and the other two are above the metal;One of them is above the metal, the other two are at the critical point between the metal and the non-metal.

In addition, it is stated in 1.2.3.2 of swp140528.pdf that the service life of the chip is 10. Is there any way to extend it to 15 years.

… some stuff got stuck in the message cache...  issue will be addressed..   Johann