Author Topic: Rigol DM3058 "Hold" trigger mode. What use is it?  (Read 2061 times)

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Offline Macbeth

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Rigol DM3058 "Hold" trigger mode. What use is it?
« on: August 13, 2015, 03:10:10 AM »
The Rigol is my first "proper" bench PSU. 

I always wondered what the RUN/HOLD button was for, other than lighting up in RUN, extinguishing in SINGLE (which does actually hold its reading), and flashing when in HOLD (which doesn't seem to hold anything at all). Reading the Chinglish documentation made mention of some formula and the settings of 0.01% - 10% in the trigger setup.

Testing with a PSU it does indeed "hold" the reading on the display until the voltage falls outside the window. For example, set the trigger to 10% and measure 10V then lower the PSU voltage. The display won't change until the PSU drops below 9V (including removing the test leads) or rises above 11V. However, it still appears to trigger anyway and records the "false" held readings in the history log. I would have thought if it was any use at all it wouldn't record more than the initial decided on "held" reading and stop recording until a measurement outside of the held range is triggered.

I just put this down as a feature important to proper electronics engineers far more worthy and knowledgable than me. I mean Rigol dedicated a whole backlit button to it and made it flash!

I recently got a Keithley 2015 and decided to give it's Hold a whirl. What do you know? It is utterly brilliant. It has the same window settings of 0.01% - 10% along with a sample count (default 5). Not only does the trigger actually work as in it only records the held reading once, but when you take the leads off it only freaking actually HOLDS the reading on the display until you go and probe somewhere else. You just place your probes wait for the beep and go and look at the display with the probes removed. The Rigol just shows the 0 volt noise like it does in regular RUN mode here.

So... WTF is this function for on the Rigol, and why has nobody else brought it up? Now I know what it should do it's implementation is an utter joke. Unless someone can tell me otherwise?  :-//
 

Online Wytnucls

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Re: Rigol DM3058 "Hold" trigger mode. What use is it?
« Reply #1 on: August 14, 2015, 06:43:49 AM »
I have the Rigol 3058E and the Keithley 2000.

On the Rigol, the 'Reading Hold' seems to work as advertised, displaying a new seed when a measurement falls outside the % set window.

On the Keithley, the 'Reading Hold' is slighly different. It also displays a new seed when a measurement falls outside the % set window, but, depending on the rate and number of samples settings, when the probes are removed from the DUT, the last measurement may remain on the screen for long enough to take note of it, the meter acting like a Fluke AutoHold.
« Last Edit: August 14, 2015, 06:46:16 AM by Wytnucls »
 

Offline Macbeth

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Re: Rigol DM3058 "Hold" trigger mode. What use is it?
« Reply #2 on: August 14, 2015, 08:04:09 AM »
But what is that used for? Also why does it hold it on the display, but carry on recording (like its not triggering at all - just running as usual) wasting data points in memory?

It clearly is something I am missing. I can only imagine something really really obscure for a "feature" like that. So why all the prominence of it being a front backlit button, flashing away to show its stuff. It must be a really important and popular function that everyone asks for to hold such prominence rather than hidden away in the trigger menu somewhere. Why is it in the trigger settings anyway? (I mean I could understand its useful for something if it stops filling memory until the trigger condition, like the Keithley, but it doesn't)

Also, does the DM3068 exhibit the same behaviour?
« Last Edit: August 14, 2015, 08:06:06 AM by Macbeth »
 

Offline Macbeth

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Re: Rigol DM3058 "Hold" trigger mode. What use is it?
« Reply #3 on: August 14, 2015, 08:30:43 AM »
...when the probes are removed from the DUT, the last measurement may remain on the screen for long enough to take note of it, the meter acting like a Fluke AutoHold.
Indeed it does. In fact I left it there all day, plenty of time to take note. It also only used 1 datapoint in the memory.

Of course for a feature like autohold to work it is important to not operate the meter in super high impedance mode as when the leads are removed the stray capacitance causes the stray voltages to ramp up as I am sure you are aware with your Keithley. So when in trigger hold mode the Keithley switches to regular 10M ohm impedance.

The Rigol manual also states that when in reading hold mode the meter is put in low impedance. This can only be for a proper autohold function to work as it only applies when the leads are removed from DUT, so why do Rigol implement this step?

Thanks for your response wytnucls, because I feel like a loner losing his mind on this one  :-DD
 

Online Wytnucls

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Re: Rigol DM3058 "Hold" trigger mode. What use is it?
« Reply #4 on: August 15, 2015, 07:45:14 AM »
The Keithley doesn't always hold the last reading with the probes disconnected. Try 10V at 10% in Fast mode with 2 samples only.

I think the problem on the Rigol DM3058 is that the number of samples cannot be set for the Reading Hold. It is stuck at a very low setting.
On the Rigol DM3068, the number of samples can be set very high for the reading Hold and it probably behaves more like the Keithley.

I suspect the DM3058 was meant to work in the same manner, but Rigol screwed it up somehow.

Most bench meters have the Reading Hold feature with the percentage setting, sometimes calling it Auto Hold, like the Agilent U1231A.
 

Offline Macbeth

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Re: Rigol DM3058 "Hold" trigger mode. What use is it?
« Reply #5 on: August 15, 2015, 10:09:23 AM »
Yes. I think they royally screwed up on this one. The keithley defaults to 5 samples, the Rigol fixed to 3. But there is more to it than that.

I reckon someone from the marketing dept. decided that the 3058 can't possibly have the same nice features as the 3068... "what can we cut? other than the 1 digit? Oh.... well, we can get rid of the trend feature.... just leave the histogram. MmmmKayy. Oh not the live histogram - make the plebs keep pressing the update button... Whats that? Allow them to trigger on a measurement window? Nononono - yes that is built into the Pass/Fail whotsmebob, but we have to remove at least 1 trigger so that will have to go... What's that - the engineers are saying its fundamental to the Reading Hold?? What do they know? Marketing knows best... it has been ordained"

...and so the 3058 "Reading Hold" is a total fail - biggest button on the meter and light flashing but utterly useless. I mean I can hold a reading just by pressing "Single" - I just need 3 hands but at least that doesn't fill up the memory buffer with useless readings.  ::)

Ok. I think I have ascertained that this is a proper fail despite your best will in the world to prove me wrong. I'm going to moan at Rigol!  |O
 

Offline Macbeth

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Re: Rigol DM3058 "Hold" trigger mode. What use is it?
« Reply #6 on: August 15, 2015, 11:15:22 AM »
I've just tried the Keithley in fast mode with no filtering (iinsanely fast) and 3 samples like the Rigol according to the user guide - 10V and 10% and it holds the reading perfectly for a good minute or so then drops and holds another "noise" reading... I think the 5 sample default is probably a good setting - the Keithley sits there all day with a reading if you let it.

Any DM3068 owners willing to explain how the hold functions on their meters? I don't recall it being shown on the Signal Path review - I'll have to watch it again. I noticed Shahriar recently reviewed the Siglent SDM3055 5.5 digit meter which is surely the competitor to the aging DM3058. He demonstrates its hold function and how it records readings into a kind of spreadsheet. Just a shame the meter is so slow! (which doesn't make sense as it is using the same 24 bit ADC as the DM3068!)
 

Online Wytnucls

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Re: Rigol DM3058 "Hold" trigger mode. What use is it?
« Reply #7 on: August 16, 2015, 02:02:29 AM »
If you want an Auto Hold on the Rigol, use the Single mode with slow speed with a trigger after 10 samples. That should give you about 5 seconds to take a measurement, leaving the probes on the DUT until the time is up. Press Single before each new measurement.
Cumbersome, but better than nothing.
 


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