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What is your interest in the Hantek DDS 3x25?

I own one
36 (27.1%)
I am considering getting one
40 (30.1%)
Curious about the hack
16 (12%)
Just passing through
41 (30.8%)

Total Members Voted: 111

Author Topic: Review: Hantek DDS 3X25. Anyone own one?  (Read 289923 times)

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Offline Mechatrommer

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #325 on: September 01, 2011, 12:07:25 am »
Sorry for a "thank you" only post.
apologize accepted :D

at msraya, do you really need 4 channel? and hence opt for usb dso (3064)? why dont get a proper dso with screen and control. or at least Hantek DSO8060 60MHz Five-in-one Handheld Oscilloscope. it got 3x25 generator (i believe), dso, multimeter (not to mention monitor and controls and handheld"ness") in one package for the price just a little bit higher than a proper low end dso alone or your suggested usb hantek 3064 oscilloscope. but if you split the price, you can average about $100+ only for each functionality. which is what i pay for the hantek 3x25 alone. if i'm looking for a generator and a scope, (with multimeter as a bonus) i may want to look at this unit. i've made a post on this sometime ago but i believe its lost in space. and since you are educating young people, in my opinion, its better not just teach the functionality, but the working with the real device interface (monitor or graticule, buttons, knobs, cabling etc), usb device only for budget limited or another alternative for people/hobbiest (or Uni?), recommending (promoting) it as real device is not a good idea... in my humble opinion.

http://cgi.ebay.com.my/Hantek-5in1-Handheld-Scopemeter-DMM-DSO-AWG-DSO8060-60M-/260839953809?pt=BI_Oscilloscopes&hash=item3cbb45d591
« Last Edit: September 01, 2011, 12:23:43 am by Mechatrommer »
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline msraya

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #326 on: September 01, 2011, 07:24:21 am »
Thank You Again, Mechatrommer. I dont know all chinese oscilloscope, I am getting the picture, HI.

In my desk, I have a old Instek GDS-820C, 150MHz wich I use all day and I want to replace. For my home and my project I  need more chanels more depth memory and MATLAB conection, then I think in the Hantek 3064A, but then I re-think than I could need more bandwith in lieu of more channels... The new OWON SDS8202 atract my attention at twice 3064A cost, 650eur, but I not find review of the more interesting OWON MSO8202T wich is also expensive for my hobby work.

Yes, the Instek has SCP Language and MATLAB conection, that Hantek does not has, then..  In the univ lab we have lots of GDS-810 with serial interface. I also have a Agilent MSO6052A in the univ lab wich I use in MATLAB via GPIB, but it is in another ligue, HI.

In the other hand, I want my students can abbord a AWG and Oscilloscope at home to practice himself. I want to build a basic electronics and DSP practice tour based in MATLAB and SCP (hantek or other). I dont know the hantek 8060. Can be the solution, but it is more expensive at aprox 370eur, vs Hantek DDS 3X25 + Hantek DSO2090 = 250eur. It has more capabilities, too..

Sorry for the OFF-TOPIC!
Greetins
Manuel

« Last Edit: September 01, 2011, 07:29:40 am by msraya »
 

Offline Kozmyk

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #327 on: September 03, 2011, 04:25:59 pm »
I'm that impressed by the GOLTEK software that I've gone and bought a Hantek 3x25.
Excellent work.
Thank you.

 

Offline Kozmyk

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #328 on: September 14, 2011, 03:37:03 pm »
3x25 arrived today.
The GolTek Controller makes it infinitely more useable.
No more stability problems.

Thanks for all your efforts. 
 

Offline saturationTopic starter

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #329 on: September 14, 2011, 04:02:34 pm »
Glad you like it Kozmyk, give us a review if you can; I know you recently had issues with the Siglent but your impression with your Kikusui, your upcoming new scope, comparing it to your current FG and any photos you can share would be nice.

3x25 arrived today.
The GolTek Controller makes it infinitely more useable.
No more stability problems.

Thanks for all your efforts. 

Best Wishes,

 Saturation
 

Offline Mechatrommer

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #330 on: October 22, 2011, 07:57:54 pm »
i've made some simple note while i'm at it. FWIW. DDS3X25 as Digital Generator
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline saturationTopic starter

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #331 on: October 26, 2011, 03:12:55 pm »
Nice!  Thanks for that mecha. 

i've made some simple note while i'm at it. FWIW. DDS3X25 as Digital Generator

Best Wishes,

 Saturation
 

Offline Tectonic

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #332 on: November 24, 2011, 07:17:21 pm »
You can add me to the list of 3x25 owners. Praises to you Mechatrommer, for your GolTek Controller. Also thanks to all the helpful contributions from other members.

So far the 3x25 is exceeding all my expectations. I've been searching for a decent function generator to play with while I'm learning Robotics and this is a true gem in its price range. I searched for affordable used bench top models as well as new devices at entry level pricing. This proved to be more complicated than I had anticipated by a few orders of magnitude!

I do have a few questions for you guys in regards to the signal output I see on my scope. The first Picture is of a 5MHz square wave. Output impedance from the GolTek Controller is set to 50ohm. The oscilloscope is an 400MHz analog Tektronix 2465B calibrated about 3 years ago.





This second picture is of the same square 5MHz wave. This time I'm using a P6139A probe connected to a Pomona BNC to minigrabber test clip, which is plugged in directly to the 3x25. Impedance is still set to 50ohm.




And now the same signal using the probe but reducing impedance to 1ohm.











In the first picture, what I think I'm seeing is over input impedance. I believe I'm seeing something similar to what's noted in Linear Technology's AN47-14 (pdf). The third picture using the probe and the impedance set to 1ohm also shows the curve at the top of the rising edge and bottom of the fall.

If this is indeed caused by over input impedance, is there a way to compensate even further via software? Also of note is the amount of ringing.
 

alm

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #333 on: November 24, 2011, 10:31:55 pm »
I do have a few questions for you guys in regards to the signal output I see on my scope. The first Picture is of a 5MHz square wave. Output impedance from the GolTek Controller is set to 50ohm. The oscilloscope is an 400MHz analog Tektronix 2465B calibrated about 3 years ago.
Rise time of about 5ns, seems reasonable (not sure what the rise time spec is). Is the scope set to 1 Mohm or 50 ohm? A 50 ohm input impedance should give the best performance. The impedance setting in the generator will probably only change the amplitude calibration. Eg. if the output impedance is 50 ohm, you expect half the amplitude with 50 ohm load, and the full amplitude with 1 Mohm load.

This second picture is of the same square 5MHz wave. This time I'm using a P6139A probe connected to a Pomona BNC to minigrabber test clip, which is plugged in directly to the 3x25. Impedance is still set to 50ohm.
I wouldn't expect a great signal when using some flying leads, I would only use coaxial connections. If you don't have a probe tip to BNC adapter, try putting the probe tip directly in the BNC socket and make a short ground connection (not the alligator clip) between the probe sleeve (unscrew the plastic part) and BNC shell. Twisting a cut off resistor lead around the ground sleeve might work. The less inductance, the better.

And now the same signal using the probe but reducing impedance to 1ohm.
Reducing impedance to 1 ohm? You mean putting a 1 ohm resistor in parallel with the probe? Or some setting in the software?
 

Offline Tectonic

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #334 on: November 24, 2011, 10:42:57 pm »
With the BNC cable, the scope is set to 50ohm. With the probe the scope is at 1Mohm. I reduced it to 1ohm via software.

Edit: The adapter was the problem as you suggested. I used the probe directly on the 3x25 and the wave looks similar to the one I get in the first picture with the BNC cable.
« Last Edit: November 24, 2011, 11:01:33 pm by Tectonic »
 

alm

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #335 on: November 24, 2011, 10:55:55 pm »
Shafri would know for sure, but I would expect the only result to be that the software does some mathematics to convert the amplitude display. 1 ohm output impedance sounds unlikely, that would suggest a huge short circuit current. It's also very uncommon for generators to actually have a variable output impedance.
 

Offline Tectonic

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #336 on: November 24, 2011, 11:11:20 pm »
As far as I know the Spartan 3 has digitally controlled impedance functionality. I can't be certain if this is how the GolTek Controller varies output impedance though.
 

Offline Mechatrommer

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #337 on: November 25, 2011, 12:03:44 am »
With the BNC cable, the scope is set to 50ohm. With the probe the scope is at 1Mohm. I reduced it to 1ohm via software.

preface:
software is a software, it got nothing to do with hardware. goltek cannot control the hardware impedance, there's no API for that. if you look at teardown in the early page, dds3x25 only has fixed 50ohm output impedance, ie small resistor just before the bnc connector output. by changing impedance in software, it will not affect anything in the hardware.

"postface":
what impedance means in goltek is that... in reality, at what impedance you are loading the generator? (a resistor between the 3x25 output and the ground, it also called termination) if you set your scope to 50ohm (scope's input impedance), then you are loading the 3x25 with 50ohm, then you should put 50ohm value in software. if you put a 1 ohm termination at the probe, then put 1ohm in goltek, not the other way around, dont expect by putting 1ohm in software, there will be a 1 ohm resistor popped out somewhere in reality.

impedance value in software is only try to display/simulate/predict the signal magnitude correctly... you have to match the impedance in real world, with the impedance value in software so that the little "monitor like" figure simulating output signal in your PC, will show you the closest thing with the real signal out of the 3x25. i hope i understand your problem correctly and answered it. ;)
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline Mechatrommer

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #338 on: November 25, 2011, 12:27:34 am »
as of your picture. the 1st picture is scope impedance set to 50ohm (software at full magnitude), the 3rd picture the scope is set to 1MOhm impedance (and again software at full magnitude), and the 2nd picture is some reflection from the pomona lose wires probe or else the goltek already change amplitude setting to lower value due to you are playing around with "software impedance". am i right? i suggest you redo test in 2nd picture, but make sure magnitude setting in goltek is set at maximum, if the pomona+scope impedance = 1MOhm, you should see 6Vpp (similar to 3rd picture, or 3Vpp like in 1st picture if your probe+scope "real" impedance is 50ohm) but noisy wave (noise due to improper probe setup, ie lose wires), hint: to get max magnitude in goltek, just type crazy large value such as 1000V and hit enter, goltek will automatically set to max magnitude sensible by the API (hence DDS hardware). and make sure Flat Ctrl is turned OFF if you want max 6Vpp out of 3x25 (Hi-Z output)
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline rev0

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #339 on: November 28, 2011, 07:18:34 am »
as of your picture. the 1st picture is scope impedance set to 50ohm (software at full magnitude), the 3rd picture the scope is set to 1MOhm impedance (and again software at full magnitude), and the 2nd picture is some reflection from the pomona lose wires probe or else the goltek already change amplitude setting to lower value due to you are playing around with "software impedance". am i right? i suggest you redo test in 2nd picture, but make sure magnitude setting in goltek is set at maximum, if the pomona+scope impedance = 1MOhm, you should see 6Vpp (similar to 3rd picture, or 3Vpp like in 1st picture if your probe+scope "real" impedance is 50ohm) but noisy wave (noise due to improper probe setup, ie lose wires), hint: to get max magnitude in goltek, just type crazy large value such as 1000V and hit enter, goltek will automatically set to max magnitude sensible by the API (hence DDS hardware). and make sure Flat Ctrl is turned OFF if you want max 6Vpp out of 3x25 (Hi-Z output)

I'd like to suggest the addition of a PWM waveform option on your Goltek program. I don't yet own a 3x25, but just ordered one, and I think that a variable frequency and duty cycle PWM output would be extremely useful (I usually end up programming an AVR to do this, but I waste a lot of time hooking one up and digging out the right config register values).
 

Offline Mechatrommer

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #340 on: November 28, 2011, 02:38:57 pm »
I'd like to suggest the addition of a PWM waveform option on your Goltek program.
very good idea! i'll see what can i do and how to fit it in the program.
edit: about the AVR, i think you can program it with one adc input (trimpot) and the pwm output duty cycle will change based on the trimpot value.
« Last Edit: November 28, 2011, 02:52:23 pm by Mechatrommer »
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline RJSC

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #341 on: December 04, 2011, 11:53:31 pm »
This topic is getting a bit long to read straight from the beginning, but I understand that with the GolTek software, the jitter and sync issues are resolved, right?

Has anyone designed an amplifier so that we can use the DDS 3X25 over an wider amplitude and offset range?

Maybe we can design an amplifier that can be connected to the pattern generator port and be controlled by the Goltek software.
Hows that?
 

Offline Mechatrommer

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #342 on: December 05, 2011, 10:10:53 am »
but I understand that with the GolTek software, the jitter and sync issues are resolved, right?
synch issue solved, with limitation (freq res/step). jitter? no, its inherent in fpga dds hardware.

Has anyone designed an amplifier so that we can use the DDS 3X25 over an wider amplitude and offset range?
if you have a taste for it, you may ask me for schematics... http://soasystem.com/eng/goltek/amplifier.htm its just normal 3-5X gain opamp using ths3095

Maybe we can design an amplifier that can be connected to the pattern generator port and be controlled by the Goltek software.
already has, in the dds3x25 hardware. whats the point building what you already have? the only sensible to me is for digital generator (bus, spi or such). but i have a hardtime finding time for sw dev for it sorry :P
« Last Edit: December 05, 2011, 10:14:15 am by Mechatrommer »
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline Amerlock

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #343 on: January 14, 2012, 06:57:14 am »
Hello everyone,

First off I would like to say what a great Forum. Now a little about myself.. I am doing a double major in Engineering (computer and Electronic).. And I have decided to build my own lab at home so that I may be close to my kids while I am doing my homework.

Anyways, within the last couple of weeks I have purchased all of my equipment and everything seems to work fine except the DDS 3x25.. I have realized that we cannot regulate the impedance. The equipment at school lets us put a HIGH Z function on route for the impedance control. And it is too late for me to return my function generator. So my question is this..

Would it be possible for you to incorporate a similar HIGH Z function into your Goltek program?  And if not could someone recomend some way of getting around this problem with the DDS 3x25. If I cannot find a solution for this I might as well resell this piece of equipment because it will be useless to me and find another one that suits more my needs..

Thanks for any help..
 

alm

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #344 on: January 14, 2012, 07:41:05 am »
Anyways, within the last couple of weeks I have purchased all of my equipment and everything seems to work fine except the DDS 3x25.. I have realized that we cannot regulate the impedance. The equipment at school lets us put a HIGH Z function on route for the impedance control. And it is too late for me to return my function generator.
Did that actually change the output impedance, or did it just scale the displayed voltages to be correct for an unloaded output, like most of the function generators? I find it hard to understand how this can be a critical feature, didn't they teach Ohm's law in school?
 

Offline saturationTopic starter

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #345 on: January 14, 2012, 01:11:03 pm »
Typically a Hi-Z switch on a FG, effectively replaces the 50 ohms in series with 1 megaohm resistance.  To emulate the same simply put a 1 megaohm resistor in series with the Hantek 3x25 output.  The only reason to have this is so the function generator output voltage matches the output scale of the FG, otherwise, it typically 2x larger than the FG scale.  It uses 1 megaohm to match what its commonly used for; to see on a scope.

In theory, Hi-Z can mean infinite impedance such as in tristate buffer ICs.  But if that were so, anything in series with it will see zero output. 

The 3x25 is best used by someone who enjoys hacking and exploring how to stretch gear without fear.  Its not the ideal instrument for teaching, because it does peculiar things that had to be hacked around.
Best Wishes,

 Saturation
 

alm

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #346 on: January 14, 2012, 01:38:28 pm »
Typically a Hi-Z switch on a FG, effectively replaces the 50 ohms in series with 1 megaohm resistance.  To emulate the same simply put a 1 megaohm resistor in series with the Hantek 3x25 output.  The only reason to have this is so the function generator output voltage matches the output scale of the FG, otherwise, it typically 2x larger than the FG scale.  It uses 1 megaohm to match what its commonly used for; to see on a scope.
Do you have an example of a function generator that actually does this, preferably with schematic? This sounds like a dumb thing to do. Where do I buy the 1 Mohm coax cable that matches the impedance of this supposed 1 Mohm output impedance? Assume I use a 1 meter RG-58C cable to connect the function gen to the scope, and the function generator is set to its max (3.5V) amplitude. This unterminated piece of coax will have a capacitance of about 100 pF, so the impedance at 75 MHz will be about 20 ohms. This will load the function gen and will reduce the amplitude at the output of the function generator from 3.5 Vp-p to about 70 uVp-p.

Plenty of function gens have the ability to switch between 50 ohm and 'hi-Z' load, the only thing it usually does is multiply the displayed voltage by two, since it was calibrated for a 50 ohm load. The output impedance is usually a constant 50 ohms. Some may be able to switch to 600 ohms for audio applications, but not 1 Mohm.
 

Offline Mechatrommer

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #347 on: January 14, 2012, 02:04:02 pm »
novel construction.
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline saturationTopic starter

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #348 on: January 15, 2012, 02:04:59 pm »
Sorry alm and mecha, brain faxt on my part, although it was partly factious in that the Hantek hack was made for people to play with, and get more value from it, not getting something very basic spoon fed to everyone. 

What I meant effectively is it forms a 1:1 voltage divider with the scopes impedance, fixing the voltage but not its effect as a transmission line.

Adding 1 megaohm could work at low frequencies, but it will play havoc as frequencies rise for all the reasons alm already makes clear, the impedance is still mismatched at least for the cable and the connectors.

Hi-Z as an abbreviation for "high impedance" is an ambiguous term ; tristate on one hand, non-50 ohm devices on another, anything over 10kohms for microphones; there could be more.

I've heared the term 'hi-z' used in conjunction with scope probes meaning specifically 1 megaohm probes.

http://www.home.agilent.com/agilent/product.jspx?nid=-34025.0.00&lc=eng&cc=US

There was once a signal generator with adjustable output impedance, as in mecha napkin'd schematic:

http://www.emchire.co.uk/products/product-code/506

Finally hi-z switch on many function generators just means the electronics adjusts the output so the dial scale is what is actually outputted if the DUT is not 50 ohms, it does not really adjust the output impedance of the function generator to 'high impedance'.  It can just blatantly halve it, or better, may have a voltmeter at the output that will sense, feedback and adjust the output regardless of what the DUT impedance is.
 




Typically a Hi-Z switch on a FG, effectively replaces the 50 ohms in series with 1 megaohm resistance.  To emulate the same simply put a 1 megaohm resistor in series with the Hantek 3x25 output.  The only reason to have this is so the function generator output voltage matches the output scale of the FG, otherwise, it typically 2x larger than the FG scale.  It uses 1 megaohm to match what its commonly used for; to see on a scope.
Do you have an example of a function generator that actually does this, preferably with schematic? This sounds like a dumb thing to do. Where do I buy the 1 Mohm coax cable that matches the impedance of this supposed 1 Mohm output impedance? Assume I use a 1 meter RG-58C cable to connect the function gen to the scope, and the function generator is set to its max (3.5V) amplitude. This unterminated piece of coax will have a capacitance of about 100 pF, so the impedance at 75 MHz will be about 20 ohms. This will load the function gen and will reduce the amplitude at the output of the function generator from 3.5 Vp-p to about 70 uVp-p.

Plenty of function gens have the ability to switch between 50 ohm and 'hi-Z' load, the only thing it usually does is multiply the displayed voltage by two, since it was calibrated for a 50 ohm load. The output impedance is usually a constant 50 ohms. Some may be able to switch to 600 ohms for audio applications, but not 1 Mohm.
Best Wishes,

 Saturation
 

alm

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Re: Review: Hantek DDS 3X25. Anyone own one?
« Reply #349 on: January 15, 2012, 03:33:40 pm »
Hi-Z as an abbreviation for "high impedance" is an ambiguous term ; tristate on one hand, non-50 ohm devices on another, anything over 10kohms for microphones; there could be more.
No worse than high frequency or high voltage. High frequency may be anything over 20 kHz to an audio guy, anything >> 60 Hz for a power supply designer, ~30 MHz for a ham or 100 GHz for someone working in the microwave spectrum. High voltage may mean anything > SELV for many low power electronics people, but may be > 1 kV for an electrician or > 35 kV for a lineman.

In this context it means >> 50 ohm (assumed to be infinite), similar to the open terminal voltage of a Thevenin circuit.

I've heared the term 'hi-z' used in conjunction with scope probes meaning specifically 1 megaohm probes.
With scope probes they basically mean >> 50 ohm, although the essential difference between hi-Z and lo-Z is that lo-Z are resistive transmission lines, while hi-Z are essentially capacitive dividers at higher frequencies. A Hi-Z probe may have an input impedance of 10 Mohm // 10 pF (10x probe), or 20 kohm // < 1 pF (active probe connected to a 50 ohm scope input). A lo-Z probe may be 5 kohm (100x probe).

There was once a signal generator with adjustable output impedance, as in mecha napkin'd schematic:
http://www.emchire.co.uk/products/product-code/506
A fair number of them have a switch between 50 and 600 ohm. Some HP generator were available in both 50 ohm and 75 ohm versions, although changing this requires you to replace some components.

Finally hi-z switch on many function generators just means the electronics adjusts the output so the dial scale is what is actually outputted if the DUT is not 50 ohms, it does not really adjust the output impedance of the function generator to 'high impedance'.  It can just blatantly halve it, or better, may have a voltmeter at the output that will sense, feedback and adjust the output regardless of what the DUT impedance is.
The majority of them will just double the voltage, external leveling is usually reserved for specialized applications that require it, like the Tek SG504.
 


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