Haasoscope

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Nov 29, 2017

Latest Board Design & Lock in Amplifier Demo

Hi Haasoscope fans!

Thanks to your support we’ve already reached 90% funded, with 2 weeks still left to go! Please post / tweet / share, to spread the word, and help get this project funded.

The prototype is very advanced now - take a look at the latest board I just sent to the fab:

I’ve also spent some time last week working on a quite new use for the Haasoscope - thanks to an idea from a fellow professor here at NYU - a lock in amplifier. The idea is to measure the phase and amplitude of an input signal, with respect to a reference signal. You can read more about lock-in’s here: https://en.wikipedia.org/wiki/Lock-in_amplifier

A standard lock in usually goes for ~$5,000, but the Haasoscope can do a pretty good job of it!

For instance, here’s two 250 kHz sine waves, from ch1 and ch2 of my signal generator, as seen by the Haasoscope:

If you were to shift one of those waves to the right or left, that’s changing the relative phase of the waves. This could happen, for instance, by having a longer path one signal needs to take, by going through a material with a larger index of refraction, or whatever. I’ve implemented the lockin calculation, which basically multiplies the two waves together, like vectors. (It also multiplies it by the reference wave shifted by 90 deg, to get the distance on the imaginary axis.) Here’s a plot from the Haasoscope software of adjusting the phase by just +- 1 degree:

It’s so sensitive I can even tell that one of my BNC cables is 6’ longer than the other! (The phase is offset by ~1 deg. 6’ is about 12 ns, since the signal travels at about c/2 in a BNC cable. And a phase of 1 deg for 250 kHz is 4000 ns / 360 = ~11 ns.)

It also calculates the amplitude of the wave relative to the reference wave - so signals of the same frequency have large amplitude, but those of other frequencies have small amplitude. This is where the “lock in” amplifier gets its name - it only gives large amplitude for signals that have the same frequency as the reference signal (or very close to it). It’s like a very narrow bandpass filter. Here’s a plot from the Haasoscope of varying the signal by just 0.1kHz, vs the 250 kHz reference:

Even frequencies that differ from the reference by just ~0.1% have much lower amplitude. And by 0.5% difference from the reference they have nearly zero amplitude.

Now doing all this offline in python would is easy, but it’s slow! You have to read out all those samples (256kb!) for each measurement, so at most you could measure the phase a few times per second, and you’d burn a hole through your CPU! But the Haasoscope can easily calculate the phase and amplitude in the FPGA, so you just have to read out the calculated phase and amplitude, which is 16 bits. It can thus measure the phase and amplitude about 500 times per second, with no CPU!

The professor I mentioned above is interested in using this to measure an acoustic hologram. I’m not totally sure what that means yet either - but the idea is basically to detect and move 3D objects by measuring with a microphone how the phase of a reference sound from a speaker is modified by an object, due to different speed of sound in the object vs air. And the lock-in will only hear frequencies very close to the reference frequency, so ambient noise will have little effect, since it’s at many frequencies!

Here’s a video of what you can do with these things: https://youtu.be/s5r2nmvxA4s

Neat!

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Dec 14

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Product Choices

$5

Support Us!


$149

The Haasoscope Bundle

Receive 1 Haasoscope + 2 probes + USB-serial adapter + USB blaster + screen


$119

Your very own Haasoscope!

A fully assembled Haasoscope, preloaded with firmware and ready for data-taking! You also might want to grab a USB-serial adapter (for interfacing to a computer) and/or a USB-blaster (for reprogramming the firmware). Haasoscope will retail for $119 after the end of the campaign.


$229

Haasoscopes are happier together - get two!

Two fully assembled Haasoscopes, preloaded with firmware and ready for data-taking! Again you may want a serial adapter and/or USB-blaster, but you just need one of each for both of them. The 2-pack will retail for $229 after the end of the campaign.


$429

Now we're talking about a serious data-acquisition system - 4 Haasoscopes!

Four fully assembled Haasoscopes, preloaded with firmware and ready for data-taking! Again you may want a serial adapter and/or USB-blaster, but you just need one of each for all four of them. The 4-pack will retail for $429 after the end of the campaign.


$5

USB-serial Adapter

This plugs into your computer (USB port) and then connects to the right side of the Haasoscope (serial RX/TX). It also can power the Haasoscope. You need one of these if your computer doesn't have a serial port, which is almost all modern computers. Arduinos and Raspberry Pi's do talk serial though - you can use them to read out the Haasoscope without an adapter!


$9

USB-blaster

This lets you reprogram the Haasoscope FPGA firmware from either Windows or Linux using the free Altera Quartus II software via the JTAG connector.


$9

A Cool Screen!

This is a 0.96" 128X64 pixel white OLED screen. It communicates with the Haasoscope over an SPI interface, and can show ADC data from a selected channel, or whatever you tell it to! It can plug directly into the header above the FPGA.


$16

Oscilloscope Probes

Two passive 100 MHz bandwidth oscilloscope probes for connecting to Haasoscope 100 MHz ADC inputs using BNC.


$26

Opto-isolated USB-serial Adapter

For those of you probing some dangerous stuff, you can now act crazy without killing your laptop. This USB-serial adapter works just like the standard one, but is opto-isolated, for 1500V of protection!


$15

High-speed USB Readout Board

In case 1.5 Mb/s is not enough bandwidth for you, grab one of these boards and have high-speed USB2 output from a Haasoscope! Using just 8+2 digital outputs on the Haasoscope, you can get about 4 MB/s, about 20x faster than serial, and still use the same python readout code. It's supported in the stock firmware too! Using 8+4 digital outputs, you could in theory even get up to 40 MB/s using C++ readout code and the free FTDI USB libraries.


$35

A Haasoscope Mug!

Drink your coffee in style and support the Haasoscope dream.

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Credits

Andy Haas

I teach physics at NYU. I use electronics for research, in teaching, and as a hobby.


Andrew Haas


Seeed Studio

PCBA Manufacturer

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