| Products > Test Equipment |
| Most accurate signal generator |
| << < (25/34) > >> |
| loop123:
--- Quote from: Anthocyanina on March 27, 2024, 02:40:48 am ---for your original 200$ budget, i would get an owon HDS242S. it's a very reasonable oscilloscope, multimeter and generator for the price, here's the owon's generator in yellow, vs a keysight 33212a in blue, both set for the same frequency and amplitude of 1.8vpp. you can see the measured Vpp and frequency for both channels to the right of the waveforms. keep in mind that the output of both generators is going to a high impedance load (the analog discovery's 1Mohm inputs) and will be halved if you connect them to a 50 ohm load. the owon can output 5vpp to high impedance loads and 2.5vpp to 50 ohm loads, so if that doesn't work for you, then yeah, this won't work, but within that voltage range, the generator of the owon is pretty reasonable for the frequency range you want, and you also get an oscilloscope and multimeter. --- End quote --- You said "the owon can output 5vpp to high impedance loads and 2.5vpp to 50 ohm loads". I need the 5vpp voltage bec it would be at least 1.76V rms for the E1DA. How does it calibrate 5vpp for 1Mohm load and 2.5vpp for 50 ohm load? What if my load or amplifier has arbitrary input impedance like 10,000 Megaohm in the case of my BMA-200 (see below) or 640 Ohm for my E1DA ADC? how do you compute the voltage output for those impedances? what if I will use a 1Mega ohm resistor in parallel to the output of the Owon HDS242S to be sure the load would be 1Mega ohm for unknown input impedance like my USBamp? I think the Owon with all in one function would be more useful. The RF attenuator can wait. |
| gf:
--- Quote from: loop123 on April 03, 2024, 02:00:46 am ---Member "gf" told me not make another thread so I post this question here. --- End quote --- I rather meant that all this stuff would better fit into your "Audio ADC" thread which already did exist before. These questions are not related to the topic "Most accurate signal generator". --- Quote ---There is another topic that I've been thinking for over a month. Can you share any software that can demonstrate the power of digital filter especially oversampling that can apply lowpass or bandpass filter with brick wall frequency response. My BMA-200 that uses the AMP01 has 2 order Butterworth filter with -12dB/octave response while my gtec USBamp has no amplifier but only ADC that directly maps the microvolt signal at +- 250mV. I'd like to know if it's oversampling (ability to do moving averages) capability can make me see signal that I can't with the BMA (between 1 to 2400Hz), and worth spending $3000 just to get the software to run it. Here is the spec of the USBamp. Pls share sofware to demonstrate the power of oversampling via digital filter. How much can it beat 2 order Butterworth filter with its almost brick wall response?" Remember that a 2nd order Butterworth filter with less vertical low-pass edge only adds about 7.5% noise compared to the digital brick-wall filter. --- End quote --- You answer the question yourself. The equivalent noise bandwidth of a 2nd order Butterworth is about 1.08 x cut-off frequency, so the difference is not large. If your Butterworth filter is not digital, but resides in the analog frontend, then additional noise may be introduced in the signal path between the filter and the ADC (including ADC noise). Then an additional digital filter may help if you don't need to full 0...sample_rate/2 bandwidth. [ But don't overreact before you have evidence that this is really relevant in your setup -- it could also be negligible. ] --- Quote ---So does digital filter oversampling only remove the noise above the cut-off... --- End quote --- Any filter removes (or better say attenuates) frequencies outside its passband. A filter cannot distinguish useful signal and noise, but only frequencies. Consequently, without attenuating components of the useful signal as well, a filter can only eliminate/reduce noise in a frequency band which is not covered by the useful signal. --- Quote ---https://www.gtec.at/product/gusbamp-research/ "Each of the 16 analog to digital converters operates at 2.4576 MHz. Oversampling 64 times yields the internal sampling rate of 38,400 Hz (per channel and for all channels!). In addition, a powerful floating point Digital Signal Processor performs oversampling and real-time filtering of the biosignal data (between 0 Hz – 2,400 Hz). Therefore, a typical sampling frequency of 256 Hz yields an oversampling rate of 9,600. This results in a very high signal to noise ratio, which is especially critical when recording evoked potentials (EP) in the EEG or identifying small amplitude changes in high-resolution ECG recordings. You are measuring far below the noise-range of conventional amplifiers." --- End quote --- Any delta-sigma ADC is based on oversampling and subsequent decimation to the output sample rate (which implies digital filtering), and that includes all today's audio ADCs. That's not special, but that's simply how a delta-sigma ADC works. And the mentioned "typical sampling frequency of 256 Hz" is not suitable for you, as it would limit the bandwidth to 128Hz (theoretically, and in practice even less, say 100...120Hz), but you want 1000Hz bandwidth for the useful signal. The low sample rate is not relevantt anyway for the noise consideration, but only filtering matters, and filtering can be done at a higher sample rate, too [although it requires more processing resources then]. |
| gf:
--- Quote from: loop123 on April 03, 2024, 07:31:17 am --- --- Quote from: Anthocyanina on March 27, 2024, 02:40:48 am ---for your original 200$ budget, i would get an owon HDS242S. it's a very reasonable oscilloscope, multimeter and generator for the price, here's the owon's generator in yellow, vs a keysight 33212a in blue, both set for the same frequency and amplitude of 1.8vpp. you can see the measured Vpp and frequency for both channels to the right of the waveforms. keep in mind that the output of both generators is going to a high impedance load (the analog discovery's 1Mohm inputs) and will be halved if you connect them to a 50 ohm load. the owon can output 5vpp to high impedance loads and 2.5vpp to 50 ohm loads, so if that doesn't work for you, then yeah, this won't work, but within that voltage range, the generator of the owon is pretty reasonable for the frequency range you want, and you also get an oscilloscope and multimeter. --- End quote --- You said "the owon can output 5vpp to high impedance loads and 2.5vpp to 50 ohm loads". I need the 5vpp voltage bec it would be at least 1.76V rms for the E1DA. How does it calibrate 5vpp for 1Mohm load and 2.5vpp for 50 ohm load? What if my load or amplifier has arbitrary input impedance like 10,000 Megaohm in the case of my BMA-200 (see below) or 640 Ohm for my E1DA ADC? how do you compute the voltage output for those impedances? --- End quote --- Consider the generator as a voltage source (which supplies the no-load voltage up to 5Vpp) in series with a 50 Ohm resistor. The 50 Ohm source resistance and the load resistance form a voltage divider. Example: If the load is 50 Ohm, then you get a 50 Ohm : 50 Ohm divider, and the voltage across the load is (50 / (50 + 50)) times the generator's no-load voltage. For 640 Ohm load, the voltage across the load will be (640 / (50 + 640)) times the no-load voltage. --- Quote ---what if I will use a 1Mega ohm resistor in parallel to the output of the Owon HDS242S to be sure the load would be 1Mega ohm for unknown input impedance like my USBamp? --- End quote --- Any load greater than 10 kOhms can be considered to be virtually "no load" and the error will be less than 0.5%. So don't worry when you connect high impedance loads. |
| loop123:
Is the Owon HDS242S the best 3 in 1 there is (Oscilloscope, Multimeter, Signal Generator combined) in the $200 price range? Any other alternative? Once I get it. I'll use it for the next 20 years. My multimeter is 20 years old. My pocket Oscilloscope f-NiRSi DSO-TC3 is not working, and I need Signal generator for occasional calibration. Can its oscilloscope mode be even better than my E1DA Cosmos ADC + Audacity combo or inferior? My amp output is between 0.3V to 2V peak to peak. |
| Aldo22:
--- Quote from: loop123 on April 03, 2024, 10:39:16 am ---Is the Owon HDS242S the best 3 in 1 there is (...) in the $200 price range? --- End quote --- Do you mean USD or CAD? The HDS242S does not cost USD 200. https://www.aliexpress.com/item/1005006068203110.html Whether something is "the best" depends on what you need it for. For example, it has a 14bit / 8 kpts signal generator (good), but only max 2.5Vpp (maybe a bit low). --- Quote from: loop123 on April 03, 2024, 10:39:16 am ---Once I get it. I'll use it for the next 20 years --- End quote --- Are you sure about that? A lot happens in 20 years... ;) |
| Navigation |
| Message Index |
| Next page |
| Previous page |