Other Parts Discussed in Thread: LDC1612
Hello TI Team,
We are a company from India using LDC1612 for detection of a moving metal wheel. We had used LDC1000 for same application and had faced lot of problems in reading Rp values at different temperatures. Hence we have developed our product using LDC1612. We had already sent queries to this blog and received some input also. However currently we are facing the same problem of drift in inductance values received by LDC1612 in outside environmental conditions. The environmental conditions are as follows
Temperature - (20 degree celsius - 35 degree celcius).
*Interference of Railway Electrified area(25kVA) .
We are using the recommended c0g capacitors for LC circuit. The configuration of our device is as follows
LDC1 - Capacitor - 220pf(c0G, 1% Tolerance) , Inductance - 127uH - Spiral PCB Wound Coil, fRef - External Oscillator of 40 Mhz. Fref Divider Value - 2 , Sensor Drive Configuration(Reg - 0x1e) - 0x5500, `
LDC2 - Capacitor - 330pf(c0G, 1% Tolerance) , Inductance - 121uH - Spiral PCB Wound Coil, fRef - External Oscillator of 40 Mhz. Fref Divider Value - 2 , Sensor Drive Configuration(Reg - 0x1e) - 0x5500,
I have attached the Data Log Excel Sheet for a period of almost 24 hours in the same field condition. According to your last input given to us there should very less change in frequency . But as you can see there is a lot of change in the resultant data. What are the route causes which may resultant in this much changes. Since we are using two sensors at a distance of 140mm from each other, is there chances of interference? We have not imparted any EMI considerations into our design, can it be a resultant of the same? Kindly confirm what is the drift in temperature of LDC1612 over the same range mentioned in this message. We also request you to guide us through the mistakes in the configurations that we have implemented. Is there any special requirement to avoid these results?
We also have a doubt as to why our both the LDC Data0 are similar although there is a large change in capacitor value between each other. LDC_DEFAULT_CTR_CAP_FOR_TI.xlsx
Note - In file attached Column A, is the LDC1 Data0 and Column B is the LDC2 Data0 as received through I2C. Column C and Column D are the differences in the consecutive values in Data0 of the LDC0 and LDC1 respectively. The frequencies of the respective devices are also logged in the next column which is directly derived from the Data received. ( Ref Formula used - (Fref * Data0/ 2 ^28). We are in a critical situation where our product is developed after investment from the company and the application design is through. However we are facing a big challenge in clearing the above issue. I hope you reply to this message and guide us through future development.