Bharanidharan
- Jul 22, 2014
- 25
- Joined
- Jul 22, 2014
- Messages
- 25
Hi guys,
Summary:
I am trying to make a product that can identify defects in a metal sample using Eddy current.
For this, i am using inductor coil transducers (8 of them) of value 135uH. 4 of them are transmitters and the remaining four are receivers.
The transducers are being switched by two multiplexers ADG508. one of them for transmitters and another for receivers. I am using this so that i can increase the number of coils.
These multiplexers are controlled using Arduino UNO. Inbetween the multiplexers and the transmitters I added a Voltage to current converter circuit to increase the current flow which is upto 1 Amp. This is done using OPA552 in parallel connection.
The received signal is then precision rectified and filtered and sent to arduino.
Then the signal is processed using a software.
Problems:
1. Since I started using Voltage to current converter (transmitter) the load resistor keeps on burning out. So, i changed it to a 5W resistor of value 22 ohm (previously 22ohm with 0.2W) which now gets incredibly hot. how do i reduce this heat?
2. I am using a tank circuit with cap 470nF in parallel with the inductor. This capacitor is in series connection with the Resistor of 22 ohms. The voltage capability of this capacitor is 50V. But this also gets burned. I am not sure why?
My power supply is +/-15V and the output voltage is about 10 V or less. please some one explain why it is burning.
3. After i changed to 5W resistor, my power supply (-15V is dropping to -13V) and the (+15V remains the same). If i change both of them to 13 V then it is not dropping anymore. Can anyone explain why is it dropping? is it because of the resistor?
4. The received signals are of different voltages, after rectification and filtering i measured their voltages using the multimeter since the value will be a DC. This was working until I connected the ADC pin to the filter end which makes all the values to be constant.
The filter is RC low pass, with 470nF cap and 15 ohm resistor. the values i obtain before connecting adc are 600mv, 300mv, 200mV, 500mV and after adc is 300mV constant for all the receivers. I tried to use a 1k resistor in parallel to the filter and then send the signal to the adc, but that failed as well. Please explain why it is acting like this.
Thank you.
Summary:
I am trying to make a product that can identify defects in a metal sample using Eddy current.
For this, i am using inductor coil transducers (8 of them) of value 135uH. 4 of them are transmitters and the remaining four are receivers.
The transducers are being switched by two multiplexers ADG508. one of them for transmitters and another for receivers. I am using this so that i can increase the number of coils.
These multiplexers are controlled using Arduino UNO. Inbetween the multiplexers and the transmitters I added a Voltage to current converter circuit to increase the current flow which is upto 1 Amp. This is done using OPA552 in parallel connection.
The received signal is then precision rectified and filtered and sent to arduino.
Then the signal is processed using a software.
Problems:
1. Since I started using Voltage to current converter (transmitter) the load resistor keeps on burning out. So, i changed it to a 5W resistor of value 22 ohm (previously 22ohm with 0.2W) which now gets incredibly hot. how do i reduce this heat?
2. I am using a tank circuit with cap 470nF in parallel with the inductor. This capacitor is in series connection with the Resistor of 22 ohms. The voltage capability of this capacitor is 50V. But this also gets burned. I am not sure why?
My power supply is +/-15V and the output voltage is about 10 V or less. please some one explain why it is burning.
3. After i changed to 5W resistor, my power supply (-15V is dropping to -13V) and the (+15V remains the same). If i change both of them to 13 V then it is not dropping anymore. Can anyone explain why is it dropping? is it because of the resistor?
4. The received signals are of different voltages, after rectification and filtering i measured their voltages using the multimeter since the value will be a DC. This was working until I connected the ADC pin to the filter end which makes all the values to be constant.
The filter is RC low pass, with 470nF cap and 15 ohm resistor. the values i obtain before connecting adc are 600mv, 300mv, 200mV, 500mV and after adc is 300mV constant for all the receivers. I tried to use a 1k resistor in parallel to the filter and then send the signal to the adc, but that failed as well. Please explain why it is acting like this.
Thank you.