My Agilent 33220A function generator (bought in 2004) died yesterday, so I need a replacement. (It's too old to bother with repair, and it's time for a big upgrade anyway.)
I'm looking at a Rigol model DG1062Z. Any opinions and experience?
I was looking at that one too. It's very attractive.
But the arbitrary waveform memory is only 16 Kbytes (or samples?), which won't last long at 500 Msamps/sec. Do they really mean 16 K, or is the data sheet wrong?
The DG106Z samples at 200 or 25o Msamps/sec, and comes with 8 Mbytes (or samples?) of memory.
It's correct but you can spread the (up to) 16K points over just about any period of time up to 10^6s and it will linearly interpolate between points if desired.
I have 32 GB of DDR3 running at 1600MHz. Real cheap. Around CAD $196 on Amazon.ca That's about 196/32e3 = CAD $0.006125 per megabyte, or 163.26 megabytes per dollar.
DDR4 is even faster. 3000MHz, ~CAD $248 on Amazon.
1 GB DDR3 running at 1066 MHz is around CAD $22.
These are all overkill for the application. Slower is cheaper.
1GB DDR at 400MHz is CAD $9.59 on Amazon. I can't find anything smaller.
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Newegg is probably cheaper.
The DG4000 is 14 bits at 500MSa/s sample rate:
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PC ram is probably 32 or 64 bits, but I think memory addressing may return larger chunks. So plain 400 MHz DDR ram may deliver much higher performance than is needed for this application.
FPGA SRAM has got to be expensive. Kill the RAM and use a smaller FPGA.
More memory gives more data points and more waveforms. They can probably use an existing IC to manage the memory. A complete motherboard is probably available for under $100, so the memory management portion has got to be inexpensive.
A complete Raspberry Pi with 2 GB RAM is only CAD$47.75:
The Raspberry Pi 4 Model B is the latest product in the Raspberry Pi range, boasting a 64-bit quad core processor running at 1.5GHz, dual-band 2.4GHz and 5GHz wireless LAN, Bluetooth 5.0/BLE, true Gigabit Ethernet, and PoE capability via a separate PoE HAT.
The dual-band wireless LAN comes with modular compliance certification, allowing the board to be designed into end products with significantly reduced wireless LAN compliance testing, improving both cost and time to market.
Specifications:
1.5GHz 64-bit quad-core ARM Cortex-A72 CPU (Broadcom 2711) 2GB RAM (LPDDR4 SDRAM) - also available in 1GB and 4GB versions! On-board wireless LAN - dual-band 802.11 b/g/n/ac On-board Bluetooth 5.0 HS low-energy (BLE) 2 x USB 2.0 ports 2 x USB 3.0 ports True Gigabit Ethernet Extended 40-pin GPIO header 2x micro HDMI, 4k video 4 Pole stereo output and composite video port MIPI Camera port (CSI) MIPI Display port (DSI) microSD format for loading OS & data storage 5V/3A DC via USB type C connector 5V DC via GPIO PoE Enabled Multimedia H.265 decode (4kp60), H.264 decode (1080p60), H.264 encode (1080p30), OpenGL ES 1.1, 2.0, 3.0 graphics
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The extra RAM could be used to add new functions as well as for more data.
They could wipe the competition for not much cost.
Dynamic RAM loses data when powered off, but a cheap flash memory could be used to save the data and restore it at power on.
They won't be buying RAM from Amazon or Newegg, instead from their own sources. But the Amazon prices give an indication how cheap memory has become.
You would need a fast FIFO that can supply data for about 10 microseconds (IIRC) while the SDRAM refreshes, so about 80K bits. Plus the DDR interface logic - And a Spartan 3A FPGA with 300k bits of RAM is not expensives. Not sure if it's fast enough though, prob not.
Still if someone did an open-source RPi-based dual output function generator using one of those cheap 240 x 320 TFT displays and a PCB with the FPGA, DAC(s) etc on it, I bet it would be popular even if it didn't quite measure up to the professional product in one way or another. There is probably public domain code for the LXI functionality. Maybe it's usable. There are DDR3 interfaces on Opencores that claim to be finished.
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That's about a $50 Spartan 6 FPGA with 1M bits of RAM, and it is fast enough.
The gorgeous 7" color display, backlit buttons, rugged beautifully molded case and so on definitely don't come for free.
AFAIK, I have not tested out the output protection, probably it's no worse (or better) than the Agilent products (which use multiple paralleled power op-amps on each output - giving off significant heat at the best of times).
I actually built something sort of like this for a specialized task, using a Raspberry Pi to handle the offline tasks like loading the data. Bandwidth was << 25MHz though, so pretty lethargic.
Things have changed. RPi is now running 1.5GHz 64 bit quad core with LPDDR4 SDRAM for CAD $47.75. You can even get a compiler for Python that runs much faster.
Cases are cheap. It's the design that is expensive. The spectacular FNIRSI-
1013D dual channel 100 MHz scope is an example. It is only US $149.68 on eBay. The item number is 143879446906.
It has a 6" X 3 1/2" color touch display and blows most other scopes out of the water. Unfortunately the only manual available is for the FNIRSI-5012H, which is an older version that is not as good. I asked them yesterday for the updated manual but have not received a reply yet. When I do, I will post the link.
This scope is astonishing. It is a combination of all the best features of other scopes, plus a bunch of new things. After reading the brief manual that came with it, I was dumbfounded. Then I discovered it has an internal battery good for 10 hours of running. No more ground loop problems! I think everyone should get it. It is small enough to sit on the bench and not take up much space, yet the screen is large enough to clearly display the waveforms and measurement data.
It is so convenient to use that you will probably give up your large mainframe scope for most low frequency work under 100 MHz. As an old user of the TEK 7704 and 7904 scopes that needed a scope cart, this unit is simply amazing.
With the plethora of inexpensive high quality equipment available, now is the time to be alive if you are interested in electronics!
There are a couple of known brand combo 3-in-1 battery powered waveform gen + small screen 2-channel 70MHz oscilloscope + true-RMS DMM in a bloated DMM form factor for < $200.
Might be worth throwing in the luggage if we ever get to travel again. For fiddling around with development boards and such like it would be enough a lot of the time. They even have replacable 18650 cells in a holder.
I have a DG1032Z. There is an amplitude step (on sine wave output) of about 0.25dB at 100kHz (exactly 100kHz). If that kind of rough edge is OK - then its good value for money.
I also have a Keysight 33600A, much nicer, no rough edges - about 10x the price :-)
Some of the generators has a glitch when you change duty cycle, in which the signal disappears when the SRAM is reloaded. I do not know if it is a problem for your device
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