Rigol DMM DM858 comparison thread

[MarcelMo]

Thanks for testing this.  I assume the Front End of a 858 or 858E will be the same. I noticed also some different behavior, depending on how long the DMM is already switched on (=warm).
I my video the turning point of correct DMM reading was about 50 Volt.  But today I have managed to have it even on 60 Volt.   I seems to be, that if you increase the voltage very slowly, you might end up also with those higher DC values.
Also I confirmed that the problem doesn't appear if you already in the 100V setting (no AUTO), then everything works well.
I was just thinking :  As the 100mV and 1V ranges have in the non-AUTO setting an impedance configuration option (via Measure) of 11.2M Ohm or 10G ohm. So I was wondering if this HW design might influence the current DCV Auto problem?
Or may be better: could the Analogue Front End designed in the different way for those small ranges and the overload protection mechanism is not designed correctly for it.  (Just guessing).  It would be not nice if the HW needs to be replaced.
Anyway,  I was hoping that I was the only one with this DCV bug.     But that is not case....  Again thanks for testing!!

[bdunham7]

As the 100mV and 1V ranges have in the non-AUTO setting an impedance configuration option (via Measure) of 11.2M Ohm or 10G ohm. So I was wondering if this HW design might influence the current DCV Auto problem?

The input impedance cannot be selected in when autoranging is active?  Which impedance is it then at low voltage levels when autoranging?

[csuhi17]

As the 100mV and 1V ranges have in the non-AUTO setting an impedance configuration option (via Measure) of 11.2M Ohm or 10G ohm. So I was wondering if this HW design might influence the current DCV Auto problem?

The input impedance cannot be selected in when autoranging is active?  Which impedance is it then at low voltage levels when autoranging?

It allows you to change it only in the measurement range of 100mV ls 1V, by default 11.2M.
11.2M in auto mode, measured with another multimeter, 10M.

[Kleinstein]

The problem seems to be the way the 100 mV and 1 V range handle overload. This has 2 problems:
1) the input current gets quite high.  25 mA is really quite a lot and could even cause hardware damage from overheating from long time overload.
2) The meter does not dedect the overload condition and reads a low voltage instead. It thus does not switch to a higher range and autoranging is not working.

Especially the 1st problem is more like a hardware isssue, not so much a thing that should be handled in software. It would only be a wrong configuration (e.g. relay setting) that could be fixed in SW.
So I am afraid a real fix may need a change to the hardware. Normally the protection should be a hardware thing and not rely on the software at all.
Getting 25 mA arelady at a relatively low voltage suggest a protection with a PTC. This could also explain the slow / thermal effect when slowly increasing the voltage even more.
For only 5 digits the simpler resistor chain protection should be sufficient and the PTC part may be there primarily for the resistance measurements.

Having the auto ranging only with the 10 M input impedane mode makes some sense. The 100 mV and 1 V with high impedance modes would likely need an extra relay switching. This complicates the auto ranging.

[csuhi17]

I'm testing a little to measure how the voltage measured by Rigol, the voltage added from the power supply, and the current develop.
It seems that even after a few seconds the range of this error decreases.
For me:
At the lowest voltage.
28.90V and 25mA from the power supply
DM858 starts at 1.085V and when I leave it on, it starts to drop rapidly.
At the highest voltage.
32.91V and 33mA from the power supply
The DM858 measures a slowly decreasing voltage from 87.00mV.

If I play with it a lot, the range where it is not good has narrowed.

Good little advertisement.
(from -1000V to 25V) and (from 50V to 1000V) can be used safely, but between 25V and 50V requires extra attention.
Unfortunately, I could only test between -120V and 120V.

[JCS666]

More problems, math and auto mode don't work
It also does not maintain date and time after turning off
 

Math only work in manual mode not auto!

Yes, it is not a problem, it is a lack

It keeps the date even after I turn it off.
If you mean to set the time to be visible, then restart it and then not see it, then in the settings "Load Last" must be changed to "Last". Unfortunately, the factory settings default to Hide a Display time...

It is a problem when the equipment is connected to the network, the network time predominates and the time zone is fixed in China, it has already been resolved.

Sorry, my English is Google Translate

[UFOdriver]

Has anyone already tested the conversion of DM858E to DM858?

[ass20]

Can you send it for me, for testing modification ?

[UFOdriver]

Not working upgrade from DM858E to DM858