sujan_014
Newbie level 6
I am trying to measure distance using LVDT sensor and AD698 IC. I don't have data relating the sensor I am using. I am simply tried to copy the distance measurement with device I already have. I matched the AC input and output of my system with the device that I already have. My input AC excitation is 5 Vp-p and 17 KHz. The output is alright. But I am facing problem in my DC output. The LVDT sensor that I am using is Half bridge type. I found this out after repeatedly checking sensor terminals. Circuit I used is exact one in page 6 of AD698 datasheet.
My DC supply is +/- 15 V. I want my voltage to swing from 0 - 5 V centered at 2.5 V. I tried varying resistors R1, R2 and R3. For this I put variable resistor in place of feedback resistor R2 and offset resistor R3 and AC voltage R1. Adjusting feedback resistor R2 increased/decreased offset voltage but also changed voltage swing accordingly. I managed to get 5 V swing but offset voltage is very high (~10.8 V, voltage swing 13.5 - 8.3 v). Adjusting offset resistor has no effect on the offset voltage. Referring to other forms, I connected 1M across +15 v and -AIN, and 1M across Gnd and -AIN but still did not change. I have tried many resistor values (8K, 3K, 20K) for R3 but offset voltage is unresponsive to R3. How do I change offset voltage ?
My DC supply is +/- 15 V. I want my voltage to swing from 0 - 5 V centered at 2.5 V. I tried varying resistors R1, R2 and R3. For this I put variable resistor in place of feedback resistor R2 and offset resistor R3 and AC voltage R1. Adjusting feedback resistor R2 increased/decreased offset voltage but also changed voltage swing accordingly. I managed to get 5 V swing but offset voltage is very high (~10.8 V, voltage swing 13.5 - 8.3 v). Adjusting offset resistor has no effect on the offset voltage. Referring to other forms, I connected 1M across +15 v and -AIN, and 1M across Gnd and -AIN but still did not change. I have tried many resistor values (8K, 3K, 20K) for R3 but offset voltage is unresponsive to R3. How do I change offset voltage ?