DS1054z why so many Probe Ratios? - Page 1
Forum section: electronics / testgear

author: BlueBill
author_rank: Regular Contributor
timestamp: March 06, 2015, 05:07:56 am
content: The DS1054z has 16 probe ratios, do you really need that many on an entry level scope?0.01X 0.02X 0.05X 0.1X 0.2X 0.5X 1X 2X 5X 10X 20X 50X 100X 200X 500X 1000X

author: pickle9000
author_rank: Super Contributor
timestamp: March 06, 2015, 05:13:59 am
content: No, but parts of the firmware are shared with other scopes. Do it once across the line (cheaper that way).Think of it as a bonus.

author: LaurentR
author_rank: Frequent Contributor
timestamp: March 06, 2015, 05:57:35 am
content: Two threads down, somebody is about to acquire an inexpensive differential probe that is 20x/200x andten threads down, somebody else (must be the season) a 20x/50x/200x probe. They'll be happy to have those ratios on their scope.

author: max666
author_rank: Frequent Contributor
timestamp: March 06, 2015, 07:17:48 am
content: Better have the option in the firmware, in case you need them, than need them and don't have them. It's only a scaling factor anyway.

author: djacobow
author_rank: Super Contributor
timestamp: March 06, 2015, 08:07:19 am
content: I actually do not like these ratio settings at all. If the scope has little copper contacts for a fancy bnc shroud with pins to _tell_ the scope what the ratio is, then, sure, fine, that's convenient.But if you have to change them yourself, I think they're worse than useless. The problem is that now, in addition to having a switch on your probe, you have a switch on your scope. So you have two places you can get it wrong.I leave my scopes on 1x all the time and just do the mental math. It's not that hard.

author: dom0
author_rank: Super Contributor
timestamp: March 06, 2015, 11:55:03 am
content: Ditto, I'd made some stupid mistakes in the past with those settings and I'm not using them anymore. By the way, Tek already had rudimentary probe identification in the 70s, where a different vertical highlight bulb on the vertical amp would light up if a x10 probe is connected. Automatically, of course.

author: Howardlong
author_rank: Super Contributor
timestamp: March 06, 2015, 03:11:14 pm
content: Actually, what is worse is a switchable probe where the x1/x10 switch is too easily switched accidentally, say when removing or replacing the probe clip. Considering putting heat shrink around some of my switchable probes to leave them in x10. Not sure why anyone would need the x1 option anyway, but I'm sure there's a reason.Regarding probe readback, I'm so old in the tooth that for me it actually adds a minor complication as I have a mix of scopes and probes, some do readout, some don't. Doing x10 in my head on CROs with probes sans readout had been second nature for decades.

author: DanielS
author_rank: Frequent Contributor
timestamp: March 06, 2015, 03:52:30 pm
content: Quote from: BlueBill on March 06, 2015, 05:07:56 amThe ratios are merely scaling factor for displaying numbers on the screen. It does not cost Rigol anything to add more or less but having more does spare them the trouble of adding them back in on a model-specific basis.The most useful option (for me) would be a custom factor to calibrate out oddball gain/attenuation in my test rigs.

author: c4757p
author_rank: Super Contributor
timestamp: March 06, 2015, 04:03:26 pm
content: Quote from: DanielS on March 06, 2015, 03:52:30 pmIt's 2015, these scopes have a more powerful computer in them than my Tek 2445A did. There's no excuse for the probe factor to not bearbitrary.

author: rdl
author_rank: Super Contributor
timestamp: March 06, 2015, 04:24:39 pm
content: Quote from: Howardlong on March 06, 2015, 03:11:14 pm!!! That happens to me also. All the time. That switch should be deeply recessed and very hard to move, instead it's usually the exact opposite. Why is it even in the probe handle? I'm sure there must be some good reason it's not at the connector end and I just don't know it.

author: nixfu
author_rank: Unknown
timestamp: March 06, 2015, 04:41:19 pm
content: Quote from: rdl on March 06, 2015, 04:24:39 pmI have always had the same issue with probes on other scopes from other manufacturers as well, even some of the 'big names' that have switchable probes.That is a good idea though. As cheap as decent probes are now from China, it might make some sense to just buy extras and heatshrink/glue them into fixed multipliers, and you could use a different color heatsink for each setting.

author: nixfu
author_rank: Unknown
timestamp: March 06, 2015, 04:44:09 pm
content: Quote from: djacobow on March 06, 2015, 08:07:19 amIsn't that dangerous? Don't you lose the 1M Ohm protection at 1x? Or is that not an issue on modern scopes?

author: dom0
author_rank: Super Contributor
timestamp: March 06, 2015, 04:48:05 pm
content: Uhm, that factor is only for display purposes and doesn't change anything hardware-wise.(I personally don't bother with x1/x10 probes anymore ; x1 is totally pointless for 99.9 % of everything anyway)

author: c4757p
author_rank: Super Contributor
timestamp: March 06, 2015, 04:52:50 pm
content: Quote from: dom0 on March 06, 2015, 04:48:05 pmYup, I solve the "annoying switch" problem bynot bloody usingswitchable probes! Annoying little things...

author: AG6QR
author_rank: Frequent Contributor
timestamp: March 06, 2015, 06:02:42 pm
content: Quote from: nixfu on March 06, 2015, 04:44:09 pmLeaving a PROBE on 1x all the time would have a serious downside, mostly because it would seriously reduce your bandwidth, but also because it would reduce the ability to handle higher voltages.Leaving a SCOPE on 1x all the time would just mean you have to do mental math to figure out how many volts are represented per division. Not necessarily a problem, if you understand and remember what you're doing. In particular, changing the scale factor doesn't change any internal protection circuitry.Recall, many older analog scopes had their volts/division marks on the knobs.Is this scope at .2V/div for a 1X probe, or 2V/div for a 10X probe? How can you tell the difference? You can't, unless you look at the probe. There is absolutely no difference in the scope behavior.Modern digital scopes do the scaling internally, so they show different numbers depending on how the probe scaling is set up, but that's the only difference in their behavior.

author: MarkL
author_rank: Unknown
timestamp: March 06, 2015, 08:12:30 pm
content: Quote from: c4757p on March 06, 2015, 04:03:26 pmAnd you can add to that a DC offset that's NOT part of the computed readout so it's possible to zero out any small drift in an active probe or the front end before you take a measurement. (And I'm not talking about sitting through a self-cal here.)Another thing lost going from analog to digital.

author: Neganur
author_rank: Unknown
timestamp: March 09, 2015, 08:37:44 am
content: In my opinion this is not even enough ratios!think of the following scenario:You are using Dave's uCurrent Gold with a 5V supply and attach it to your scope.The uCurrent gives you the following ranges:Code:±2250 mAwith 1 mV/mA±2250 uAwith 1 mV/uA±2250 nAwith 1 mV/nANow, the only thing that ever changes is the probe attenuation factor and the scope input is going to be a maximum of ±2250mV.So you set your scope's vertical to something meaningful, open the probe setup menu to change it to show A instead of V and change the factor according to your selected uCurrent range:Code:with 1 mV/mA = 1 V/A = 1:1with 1 mV/uA = 1000 V/A = 0.001:1with 1 mV/nA = 0.000001:1...only to find out that the damn ratios stop at 0.01 on the low end. I find this extremely irritating. Why can I not enter arbitrary ratios?It would make my life so much easier while I use odd amplification ratios. Not everything is nicely in 1-2-5 steps.

author: max666
author_rank: Frequent Contributor
timestamp: March 09, 2015, 01:55:42 pm
content: Quote from: MarkL on March 06, 2015, 08:12:30 pmHow is it lost, due to going from analogue to digital? You can still add an arbitrary offset, by moving the waveform up and down. And don't tell me "But then it's part of the computed readout", because back in the analogue days, you didn't even have a computed readoutHowever I agree, being able to set arbitrary probe ratio and offset should be in the firmware, because it can be very handy. But programming it in would also be an incredibly simple thing to do, it's not like only analogue can do it.Might I suggest sending Rigol an email regarding a small feature request? If people show interest you might see the feature in the next firmware update. Certainly more likely to be fruitful than complaining here.

author: DanielS
author_rank: Frequent Contributor
timestamp: March 09, 2015, 04:48:48 pm
content: Quote from: nixfu on March 06, 2015, 04:44:09 pmThe 1Meg input impedance and associated protection is built into the scope. There is no way to remove that.All the 10X switch does is remove the short across a 9 meg resistor and high-pass capacitor in the probe body to reduce resistive and capacitive loading at the probe tip, giving you 10 meg total DC resistance.

author: tautech
author_rank: Super Contributor
timestamp: March 09, 2015, 06:12:16 pm
content: While not familiar with the 1054z, the range of probes both commercial and home made is large.Every attenuation range in the list can conceiveably be used.Does the 1054 have the option of V/divAND A/div for current probes?If not, this will explain the sub 1:1 ratios.For those that live in the pastdoing the calcs of the attenuation for on-screen trace amplitude, you are ignoring one of the powerful features of a DSO.For those of you that leave you probes on 1:1.De-rating with frequency, DSO max V input, DUT loading.Many scopes of yesteryear came with only 10:1 probes exactly for these reasons.C'mon guys.....learn to use your gear properly.....it's made this way to make our lives easier.

author: MarkL
author_rank: Unknown
timestamp: March 09, 2015, 08:47:57 pm
content: Quote from: max666 on March 09, 2015, 01:55:42 pmPoint taken. Nothing "lost", but rather potentially erroneous data showing up on the screen that can't be corrected by any means.But we agree. It would be quite easy for any DSO manufacturer to add such a feature. Rigol is hardly the only one that suffers from this.I'll let someone else submit a feature request to Rigol, or they can throw it in the big feature/bug thread. I returned my DS1054z because I couldn't stand the number of bugs in it. No more Rigol for me.

author: DanielS
author_rank: Frequent Contributor
timestamp: March 09, 2015, 09:35:44 pm
content: Quote from: tautech on March 09, 2015, 06:12:16 pmUsing the built-in measurements assumes that the scope has accurate sampling. As multiple people have pointed out, the DS1xxxZ series has significant DC offset issues with DC offsets on each channel changing depending on what channel combination is enabled and sometimes, even with the order in which they get enabled. On one of my DS1054Z, that error can be as bad as half a division on AC coupling, which is pretty ridiculous. DC measurements are easy to correct since you can simply subtract the offset but many other measurements require exporting memory data to a PC and applying corrections there before making measurements.

author: electr_peter
author_rank: Unknown
timestamp: March 09, 2015, 10:00:08 pm
content: Quote from: tautech on March 09, 2015, 06:12:16 pmFor Rigol DS1054Z "Amplitude Unit: The available units are W, A, V and U". Attenuation settings are from 0.01X(1:100) to 1000X(1000:1) in 1-2-5 steps.

author: tautech
author_rank: Super Contributor
timestamp: March 10, 2015, 12:07:54 am
content: Quote from: electr_peter on March 09, 2015, 10:00:08 pmAre ALL these units in each Channel menu or in Math menus?Quote from: DanielS on March 09, 2015, 09:35:44 pmYes of course one presumes the scope measurement/firmware/hardware is accurate to start with.But will the 1054z retain rated accuracy using measurements.... that is more important than what is seen on screen. DSO features are such that gone are the days of measurement by "eye", thats what the OSD is for.Eg. Set averaging on and statistics on for a prolonged measurement cycle and the check real accuracy.If it consistantly falls outside spec then the unit is faulty. End of story.

author: DanielS
author_rank: Frequent Contributor
timestamp: March 10, 2015, 12:52:24 am
content: Quote from: tautech on March 10, 2015, 12:07:54 amWhat is on the screen is every bit as important as calculated measurements: if what is displayed does not agree with built-in measurement, at least one of them is lying and this indicates an obvious flaw either in the waveform display, built-in measurement or possibly both. How long would you trust an instrument that is not self-coherent when displaying the same data in two different formats? Both the waveform and measurements are derived from the same ADC(s) and should agree within eyeball/rounding error.As for the unit label selection, it is independent for each channel including math.