PI 1234567890 PI

[liudengyuan]

The analog circuit is outdated. The analog circuit is too complicated and noisy to make an excellent detector, so I hope you can do digital pi together, so that the circuit is simple and the performance will be better

[liudengyuan]

Can we directly sample the coil with a 24-bit ADC chip without using an operational amplifier?

[waltr]

Can your ADC handle 400V coil kick-back spike???

[Carl-NC]

Can we directly sample the coil with a 24-bit ADC chip without using an operational amplifier?

Have you done a noise analysis for each design, with a preamp and without a preamp?

[liudengyuan]

Have you done a noise analysis for each design, with a preamp and without a preamp?

I have measured the waveforms at both ends of the coil. In the absence of a preamplifier, the noise is very small. Of course, the voltage at both ends of the coil I am referring to is limited by a damping resistor and a diode.

[green]

I have measured the waveforms at both ends of the coil. In the absence of a preamplifier, the noise is very small. Of course, the voltage at both ends of the coil I am referring to is limited by a damping resistor and a diode.

Don't know if there is a better way. I look at amplifier out with Rx coil connected(coil pickup noise with amplifier noise) and with a jumper across Rx input(amplifier noise only). If amplifier noise is less than coil pickup noise, sampling coil with an A-D won't be better?

[KingJL]

Can we directly sample the coil with a 24-bit ADC chip without using an operational amplifier?

Not really... for a few basic reasons. At a minimum you need to buffer the input to the ADC to (1) provide the drive needed to drive the T/H switched capacitor(s), (2) limit the bandwidth of the ADC input to the scope of desired frequency response. Also the voltage issue addressed by @waltr needs to be considered to prevent damage to the ADC (good 24 bit ADC's are not cheap). The design parameters (gain / bandwidth ) of the input buffer will be dictated by the analysis referenced by @Carl-NC.

[Carl-NC]

I have measured the waveforms at both ends of the coil. In the absence of a preamplifier, the noise is very small. Of course, the voltage at both ends of the coil I am referring to is limited by a damping resistor and a diode.

In the absence of a preamplifier, a target response is also very small. You can't tell much by looking at the raw coil signal on a scope.

A preamp introduces noise to the overall response but so does an ADC. You need to do a noise analysis to determine whether the ADC alone (no preamp) is better than a preamp+ADC. My bet is overwhelmingly on the preamp+ADC. And if I wanted the absolute maximum depth, then my bet would be on preamp+demod+ADC.

I think you are looking for a quick easy solution (with people telling you how to do it) and there is none. Build one of the projects on the forum and experiment. You will quickly see how hard the problem is.

[liudengyuan]

In the absence of a preamplifier, a target response is also very small. You can't tell much by looking at the raw coil signal on a scope.

A preamp introduces noise to the overall response but so does an ADC. You need to do a noise analysis to determine whether the ADC alone (no preamp) is better than a preamp+ADC. My bet is overwhelmingly on the preamp+ADC. And if I wanted the absolute maximum depth, then my bet would be on preamp+demod+ADC.

I think you are looking for a quick easy solution (with people telling you how to do it) and there is none. Build one of the projects on the forum and experiment. You will quickly see how hard the problem is.

So I want to call on everyone to work together to solve many problems,