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Velleman PCSU1000 teardown and review

September 29th, 2015

I purchased Velleman PCSU1000 at "Electronics For You" shop when I had a sudden need resulted from the death of my 100 MHz Tektronix Oscilloscope. That was few years ago and the scope has been useful for debug of many of my digital problems. The scope is priced decent at $277 at amazon , and I think I purchased it for $300.

The Oscilloscope hooks to your computer on USB Port and you need to run a software to start acquiring the waveforms. It is advertised as a 60 MHz scope - but what is the reality ? Today, I took apart the scope to find the details.

Velleman_PCSU1000_compressed

A/D Converter ADC08L060

The ADC08L060 is an 8-bit 60 Mega Samples/sec A/D Converter from Texas Instruments and the scope uses two of these for each of these two channels. Now Velleman advertises its bandwidth as DC to 60 MHz +/3 dB. Even if we assume that the bandwidth of its front and is 60 Hz, can we accurately generate 60 MHz waveform by capturing at 60 Mega Samples per seconds ? Obviously not. So the first thing you need to keep in mind is that it is NOT and high frequency analog Oscilloscope. Yes - it may be ok to capture Digital 1 and 0 at high bit rate. That being said, I have used this scope to debug my analog sections of production boards ( like Microphone Audio etc). But I will not rely upon it for measurement of my power supply noise and Microphone noice etc.

ADC08L060

Xilinx Spartan XC3S50

When I looked at Spartan XC3S50 I remembered the P. Chug's FPGA Prototyping By Verilog Examples . It has the Spartan 3 FPGA - and is not even a BGA. A 50 MHz Oscillator clock the FPGA, but what surprised me was absence of any Memory hooked with the FPGA. Obviously, you can not sample faster without missing the data in the FIFO bus to USB transmission path.

Xilinx-Spartan-XC3S50

FTD FT245BL

The communication on the USB is through the FT245BL chip ( look at the top left in the picture above). It basically transfers the data from and to USB using 8 bit wide data bus.

PIC16F630

The FPGA sees to load its code through the PIC Microcontroller. But the Microcontroller could also be doing some other things in addition to loading and configuring the FPGA. Most designs have a dedicated Flash for this purpose.

PIC-microcontroller

In addition, there are a bunch of OP AMPs at the front end, some reed relays ( there are 7 of them for each channel), few buffers and of course power supply regulators. In overall, it is not bad design, considering that they have been able to come up with something that a hobby designer can use for his projects. But any serious scope ( even for 60 MHz), you will need faster A/D, and FPGA that has integrated memory - to make it useful. This is where the Sigilent's Entry level oscilloscopes come in picture .

By

Vikas Shukla

Uncategorized

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