Lock in amplifer

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JaRa_1183061
Level 2
Level 2
10 replies posted 10 sign-ins 5 replies posted

Hi, is it possible to design a Lock in amplifer in PSoC5. I want to work in operation range from 100-500kHz. One limit which I already have discovered is that I only have access to one filter block (for lowpass filtering). The main concept is shown below.

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Best regards

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lock attach
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JaRa,

Please note that PSoC analog Modulator only inverts signal amplitude (+A/-A), it is not an analog multiplier.

Also Analog Devices recently ran advertisements here for their Zero-IF radios. These are essentially high-frequency lock-in amplifiers.

I recommend reading this paper re lock-in detection first (copy attached)

Synchronous Detectors Facilitate Precision Low-Level Measurements | Analog Devices

https://www.edn.com/design-a-dsp-lock-in-amplifier-part-2-design-methodology/

The impedance analyzer project by Chris Keeser was posted on the forum long time ago. It basically used 1kHz sine for excitation, and DelSig_ADC built-in modulator to demodulate the feedback signal. Since only one DelSig_ADC is available on PSoC5, the in-phase and quadrature measurements were taken separately.

Re: Impedance Meter

You can find basic lock-in detector project using DelSig_ADC below. I am not sure how much up in frequency it can go. I tested it up to 10kHz, but the modulator "might" work at 100-500k.

Re: PSoC Today! - Synchronous Detection Detail

/odissey1

View solution in original post

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odissey1
Level 9
Level 9
First comment on KBA 1000 replies posted 750 replies posted

JaRa,

PSoC5 was designed with audio frequency operation in mind, so F <100kHz is where it operates best. It doesn't preclude from using it at higher frequencies, with some performance penalties.

If you consider a general purpose lock-in, you might noticed, that commercial systems are divided into two distinct groups: 0-100kHz, and 1-100MHz based on operation principle. That gives an idea that implementing 100-500 kHz range won't be a snap. It doesn't mean it's impossible, but haven't seen such solution on this forum.

May I ask what is application for such lock-in? Maybe other solutions using PSoC are available.

/odissey1

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I want to built an impedance analyzer. I can see that the mixer, can take frequency up to 500kHz.

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lock attach
Attachments are accessible only for community members.

JaRa,

Please note that PSoC analog Modulator only inverts signal amplitude (+A/-A), it is not an analog multiplier.

Also Analog Devices recently ran advertisements here for their Zero-IF radios. These are essentially high-frequency lock-in amplifiers.

I recommend reading this paper re lock-in detection first (copy attached)

Synchronous Detectors Facilitate Precision Low-Level Measurements | Analog Devices

https://www.edn.com/design-a-dsp-lock-in-amplifier-part-2-design-methodology/

The impedance analyzer project by Chris Keeser was posted on the forum long time ago. It basically used 1kHz sine for excitation, and DelSig_ADC built-in modulator to demodulate the feedback signal. Since only one DelSig_ADC is available on PSoC5, the in-phase and quadrature measurements were taken separately.

Re: Impedance Meter

You can find basic lock-in detector project using DelSig_ADC below. I am not sure how much up in frequency it can go. I tested it up to 10kHz, but the modulator "might" work at 100-500k.

Re: PSoC Today! - Synchronous Detection Detail

/odissey1

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