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| Rigol DM3058 "Hold" trigger mode. What use is it? |
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| Macbeth:
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? :-// |
| Wytnucls:
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. |
| Macbeth:
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? |
| Macbeth:
--- Quote from: Wytnucls on August 13, 2015, 08:43:49 pm ---...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. --- End quote --- 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 |
| Wytnucls:
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. |
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