Newbie Just Got Rigol DS1074Z-S Need Help - Page 1
Forum section: electronics / testgear

author: dellsam34
author_rank: Regular Contributor
timestamp: March 15, 2019, 09:13:20 pm
content: I received the DS1074Z-S that suppose to have a function generator but for the life of me I couldn't make it to display anything but a straight line. Does the probe needs to be connected to make the function generator work?I pushed source, clicked ch1, turned on output and set it to sine wave 1V, 1Mhz, Nothing seem to work except a straight line, I just want to make sure it is not defective.

author: Fungus
author_rank: Super Contributor
timestamp: March 15, 2019, 09:23:53 pm
content: Quote from: dellsam34 on March 15, 2019, 09:13:20 pmYes. SigGen output needs to be connected to an input to see something.(preferably with a terminated BNC cable)If you don't have BNC connectors/adapters you could connect a regular probe to output+input and hook them together. Don't expect a perfectly clean signal that way though.

author: dellsam34
author_rank: Regular Contributor
timestamp: March 16, 2019, 01:13:14 am
content: Where do I get a terminated BNC cable ?

author: Old Printer
author_rank: Frequent Contributor
timestamp: March 16, 2019, 02:35:43 am
content: I get a lot of mt stuff here:https://www.mpja.com/BNC-Cables/products/302/They are in south Florida, so am I. Any decent electronics place will have them DigiKey, Mouser etc.

author: dellsam34
author_rank: Regular Contributor
timestamp: March 16, 2019, 05:42:47 am
content: Since I work on audio and video equipment I should probably get a BNC to RCA cable for the generator. What do you think ?

author: Fungus
author_rank: Super Contributor
timestamp: March 16, 2019, 06:02:28 am
content: Quote from: dellsam34 on March 16, 2019, 05:42:47 amYes.You can also get adapters like the ones below.

author: Fungus
author_rank: Super Contributor
timestamp: March 16, 2019, 06:18:40 am
content: Quote from: dellsam34 on March 16, 2019, 01:13:14 amUsually you don't, you get a BNC cable, two 'T' pieces and two 50-ohm terminators.You can also get50 Ohm passthroughs, which are basically a 'T'+Terminator in one.

author: MarkF
author_rank: Super Contributor
timestamp: March 16, 2019, 06:19:28 am
content: You may even like something like this set on Amazon:50 ohm termination:

author: wolfp
author_rank: Contributor
timestamp: March 16, 2019, 07:08:39 am
content: 50Ohm termination is found usually in hf-applications. Because you are working with audio equipment higher values can make sense (eg. 600 Ohm or more). For video Signals sometimes 75 Ohm is used . Just build your own termination by using a BNC plug and a resistor with the desired value. Up to a few MC this is no problem.Wolfgang

author: Fungus
author_rank: Super Contributor
timestamp: March 16, 2019, 07:37:35 am
content: Quote from: wolfp on March 16, 2019, 07:08:39 amI mentioned 50 Ohm because he wanted to connect to his signal generator. The first thing most people do with those is the "Let's see how high it can go!" test.Quote from: wolfp on March 16, 2019, 07:08:39 am

author: dellsam34
author_rank: Regular Contributor
timestamp: March 16, 2019, 06:11:02 pm
content: I'm confused about this termination thing, I though the function generator just delivers a tone with a desirable voltage value, If it gets terminated doesn't that put a load on the voltage output from the function generator, Especially if the voltage desired is in the order of a mV or even a microV ??Let say I'm carrying out the test according to the service manual in the illustration below where it instructs me to deliver a frequency of 1Khz with a voltage of 0.775 mV and then observe both the oscilloscope and a VTVM (or equivalent of modern day). If I terminate my circuit wouldn't that change everything?

author: Fungus
author_rank: Super Contributor
timestamp: March 16, 2019, 06:19:53 pm
content: Quote from: dellsam34 on March 16, 2019, 06:11:02 pmYes.The idea is to avoid reflections/ghost signals in the wire.If you have a setup like this then you don't need termination. It will be very difficult for signals to reflect from one end to the other through all those devices.

author: dellsam34
author_rank: Regular Contributor
timestamp: March 16, 2019, 06:54:22 pm
content: Quote from: Fungus on March 16, 2019, 06:19:53 pmLet me be clear here, There is only one circuit in the diagram above, The record head pre amp, The playback amp is separate from the rec amp except maybe for a shared ground. Vintage reel to reel recorders have separate heads and pre amps for recording and playing back and you can monitor what you are recording on the fly.

author: Fungus
author_rank: Super Contributor
timestamp: March 16, 2019, 07:17:24 pm
content: Quote from: dellsam34 on March 16, 2019, 06:54:22 pmThere may only be one PCB but there's more than one circuit on it.The thing to note in that diagram is that there's a 100kOhm resistor between the output amplifier and the oscilloscope. This will quickly kill any signals that dare to try and bounce backwards and forwards along that wire. You probably wouldn't be able to see them anyway at audio frequencies over a few feet of cable.The best thing is to try it and see what happens. If you see faint "ghosts" of the signal on screen then you might need termination. If not, you don't.

author: dellsam34
author_rank: Regular Contributor
timestamp: March 17, 2019, 12:22:06 am
content: I just boughtthis feed thru terminatoris it any different from the $45 ones?

author: wolfp
author_rank: Contributor
timestamp: March 17, 2019, 07:26:46 am
content: For lower frequencies this feed through terminators may be usable. Using higher frequencies (> 1GHz) and a VNA you will recognise the difference.On the other hand I made some measurements up to 6 GHz, a few of these terminators seem to be astonishing good. But you never know what you get if you buy such cheep devices.Wolfgang

author: TurboTom
author_rank: Super Contributor
timestamp: March 17, 2019, 08:16:38 am
content: Sorry but for these audio-related frequencies, especially when probing around in vintage equipment, all the termination issues are BS... Inside the equipment, you will be using 10x or even 1x probes at the input(s) of your 'scope. Actually, working in audio gear is one of the very few areas where it may make sense to use switchable 10x / 1x probes and configure them to 1x.I think the termination issue was introduced since you want to measure the internal waveform generator of your scope. These generators have an output impedance of 50 ohms. Usually, you can set up the generator if it the load it's attached to is 50 ohms or high-impedance. Some generators even offer to enter arbitrary values. This doesn't change anything on the generator output, it's still 50 ohms, but it's used to calculate the signal level accordingly. As an example, if you adjust your AWG to output 1Vpp into a high impedance load (i.e. a "classic" oscilloascope probe), you will measure (more or less) exactly this level. If you configure the AWG to 50 ohm load impedance and adjust the level again to 1Vpp und still measure with the high-impedance probe, you will just measure twice the voltage (2Vpp). The AWG takes care of the voltage divider consisting of the impedance of the AWG's output stage and the load resistance the signal is (told to be) fed into.Proper termination of transmission lines (coax wires...) of the "usual" lengths becomes relevant if you are working on RF gear (say > 1MHz), or basically, if the length of the wire get longer than about 1/20th of the wavelength (on the line) of the signal. Just use your scope's probes for audio and lower RF stuff and you should be fine. Get used to it and after some time, you will know what probing technique may be required for a certain signal.What's very convenient are those BNC-alligator or clip leads for injecting signals (be careful not to touch any contacts that carry a signal and may feed it back into the AWG - this could be fatal (for tha latter that is) and always make sure the grounds the probing and sourcing leads are connected to are identical. If you can't eliminate a ground potential difference, use an audio signal isolating transformer at the AWG/s output. This will eliminate the ground loop through the oscilloscope. Alternatively, a (higher voltage) active differential probe is a very recommendable thing, look out for the MicSig ones since they are quite affordable. Yet they most useful for high(er) signal level measurements.A 50 Ohms feed-through terminator may be good to have anyway if you eventually intend to attach some other active probes that may be calibrated to feed into such a load. But it's not required right from the start.Just my 2 cents...Cheers,Thomas

author: dellsam34
author_rank: Regular Contributor
timestamp: March 18, 2019, 05:13:32 am
content: I wasn't too thrilled about terminators either, I was just concerned about the function generator, I will not be using them for probing signals. The only reason I got the oscilloscope with built in function generator is because the function gen app (for audio) I was using on my phone doesn't allow me to control the voltage output, It just allows me to control the dB output from -60dB to 0dB, As you can see from the illustration above if I go that low it is silence (0V).