| Products > Test Equipment |
| MHS-5200A function generator teardown / review / reverse engineering |
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| PoV:
Ah crap! I just bought one of these (newer 12bit model), but didn't realize I was buying the 6 MHz version instead of the 25 MHz version (was $1 cheaper). Doh! |O According to this manual I stumbled across, the only difference between models is the Sine way frequencies (all other generators seem capped at 6 MHz). Has anyone looked in to dumping/reprogramming the firmware yet? I would imagine they're exactly the same, just different firmwares. |
| BugCatcher:
I bought a MHS-5225A release R5.04 started to play with and found following "challenges": 1) Frequency Error - connect "In ext." with "ch 1" - set frequency to 20.000 000 00 MHz - run the internal frequency counter with 10s gate time -> my result is 20.000 146 3 MHz (7.3ppm deviation) Interpretation: - crystal frequency error is factory calibrated (my 7.3ppm are a device specific value) - DDS-generator is frequency corrected, frequency counter is not corrected 2) Frequency Resolution - expected 10mHz resolution at any frequency - use the setup for "Frequency Error" and try to set the frequency in a way that the counter is showing 20.000 000 0 MHz -> you will find that the frequency resolution is in the range of 1...5Hz (in an irregular fashion) Interpretation: - frequency correction is running into numerical issues - required number of discrete frequencies is 25MHz/10mHz = 2.5 x 10e9 would nicely fit into 32bit unsigned integer - my gut feeling frequency correction is using 32bit floating point format (with 25bit mantissa) -> missing 7bit -> 10mHz x 128 = 1.3Hz b.c. resolution @ max. frequency 3) deterministic square wave distortion - set generator to 1kHz square wave - connect a scope, trigger on falling edge - zoom in (e.g. 1us/div) -> you will observe a very surprising distortion! a small "bonus step" 1us in front of final falling edge height of step is approx. 12% of pp signal amplitude length of distortion is a function of frequency (approx. 0.001 * 1/f) Interpretation: I have no glue !!! 4) temperature of output driver ICs (at least for the replacement type) - they are really hot! -> strongly recomment to invest in a bigger heat sink and a small amount of thermally conductive paste My general impression: good enough entry level product at an attractive price point (even with the known impairments) Have Fun ! |
| Kleinstein:
With just R2R resistors at the FPGA output, is there a really improvement going from 8 to 12 bit - even the 8 Bit are difficult to get right. So how does a lower frequency triangle look like ? The slew rate limit is not that bad for a sine wave. Reducing the amplitude at the highest frequencies is not such a bad restriction. It is more a problem to the square wave, but here using just an NCO there is a lot of jitter anyway. So not a good square wave anyway. A good square wave would need a filter and comparator. Wondering why the use the extra AD8017 and still the AD812 for the output. They could have used the same OPs for both function. Likely the AD8017 would be slightly better for the output stage as well. |
| nickcres13:
I posted this same reply on the other relevant MHS5200A teardown/hack thread, but thought I would post here for those not in the other thread...sorry for the spamming haha. I know im late, but thought I would put in a word about some scripts im developing to further gain access to the MHS5200A device via serial commands. Namely, I have started with a dumb script that asks it for the frequency (on "EXT_IN") once a second and plots it in gnuplot. Links to the github repo and a boring video of me using it below. Let me know what needs fixed! NOTE: I compile and run on Ubuntu, should work on other Linux distros, as for Windows and hackcoughblechApple there is work to do still obviously... https://github.com/electricsheeplabs/mhs5200aDataLogger |
| techfan:
Hi, I have a question, what is the maximum continuous current (square wave 100%) that supports the equipment ?? Can be used as DC source for Arduino or Raspberry Pi 3 ?? Thanks |
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