Products > Test Equipment

Will this 2V signal damage my bench multimeter over time?

<< < (7/8) > >>

eloso:



--- Quote ---As you can see in the statistics in the images below, the input impedance is steady at around 10Mohm both at 1.9V and at 2.3V. Thus, the relay does not seem to affect input impedance.
--- End quote ---


Thanks Amaruk.  I too have revisited the measurement.

Still using the voltage across a 1Mohm resistor to calculate current flow into the Siglent when measuring 1.8V and 3.6V.  i.e. either side of the relay "click".

What is different this time is that I am using a different millivoltmeter. I measured the input resistance of this millivoltmeter with the Siglent to be a suprisingly low 800Kohm which obviously loads the 1Mohm current sensing resistor quite a bit.

Because I have learned never to trust my math  :-\   I created an LTSpice model of all of this  and the results  - both before the relay click and after the relay click, the LTSpice numbers all add up to 10Mohm input of the Siglent, matching the mV readings taken on the meter.

So no impedance change on the Siglent when the relay clicks.


I don't know what was going on with the VC8145 but on mV it was giving some very strange results. I did use a short twisted measuring probe set but maybe it was still some noise getting in.


If my latest measurement was the only one, I would probably accept it with nagging doubts, but it ties in perfectly with results obtained by Amaruk which seem beyond doubt anyway.   

So definitely no funny impedance change problem.

When that relay clicks, my VC8145 does give some totally different indication of impedance  so whether it is a bug or not, it is definitely altering something. Based on  our latest measurements I am at a loss to understand exactly what. 

The fact remains that on a manual range or auto range, if I want to measure a voltage between 2.2V and 6 volts , I have to put up with a relay click, and a delay every time I apply the probe to the DUT.  Doesn't make me proud to own, nor happy to use, this meter.

Regards

Eloso

 

Amaruk:

--- Quote from: eloso on January 01, 2022, 11:01:51 am ---
The fact remains that on a manual range or auto range, if I want to measure a voltage between 2.2V and 6 volts , I have to put up with a relay click, and a delay every time I apply the probe to the DUT.  Doesn't make me proud to own, nor happy to use, this meter.

--- End quote ---

Exactly!

You can even make the case that there is no manual 6V or 6mA DC ranges on this multimeter...

Sure, the spec sheet states that those ranges exist (see image below) and the meter allows you to select those ranges. But in reality they do not exist.

The point of a manual range is to obtain extra measurement speed (see this answer from Keysight: https://edadocs.software.keysight.com/kkbopen/what-is-the-effect-of-choosing-auto-or-manual-range-580285257.html). Thus, when a manual range is selected the meter should measure and not go between ranges. That defeats the purpose...

Hopefully it is just a firmware issue and it will get resolved quickly.

For your reference, I experienced a "severe" firmware bug with a brand new Keysight power supply not that long ago. It took their support team less then 48 hours to acknowledge and release a new firmware that had a fix in it!! (Link to thread: https://www.eevblog.com/forum/testgear/keysight-edu36311a-current-reading-bug/msg3840200/#msg3840200)

To have a firmware bug in a product is no big deal as it is very difficult to check for everything when you code. It all comes down to customer service AFTER the purchase. How quickly is something fixed? I hope Siglent can show us that their goal is to match and maybe even go beyond other companies in this industry.




eloso:

Sensible - The 3045X's other little foibles I don't mind quite as much as this one so if they are able to fix it then fine.

What is the best way to make a bug report that hopefully gets looked at?  My experience with 99% of companies out there is the real guys that know about things are protected from customers behind a wall of  people who don't.  Unpalatable but for understandable reasons of course.


Incidentally, do we know if other machines in the same range exhibit this kind of behaviour ?   Awaiting the outcome of tautech's sporting activity with the 3055 firmware with bated breath !

 
Eloso

Kleinstein:
The SDM3055 has a 2 V range as the limit for high Z mode and may thus switch ranges at 2 V in auto mode.  I don't have very much hope the 3055 firmwire would fix the problem - chances are more that accidently some of 3055 firmware made is to the 3045 in the first place and triggers the switching.
They seem to use the same base for the FW, but have still different hardware.

The question is more if this problem was allredy there with much older FW.

tautech:

--- Quote from: eloso on January 01, 2022, 05:12:30 pm ---
Sensible - The 3045X's other little foibles I don't mind quite as much as this one so if they are able to fix it then fine.

What is the best way to make a bug report that hopefully gets looked at?  My experience with 99% of companies out there is the real guys that know about things are protected from customers behind a wall of  people who don't.  Unpalatable but for understandable reasons of course.


Incidentally, do we know if other machines in the same range exhibit this kind of behaviour ?   Awaiting the outcome of tautech's sporting activity with the 3055 firmware with bated breath !

 
Eloso

--- End quote ---
I'll report it when I have further info and write something up. I too strongly suspect a bug.

Sporting activity status:
Still doing due diligence on internal difference between models.
Need to further investigate the China only SDM3055X-E datasheet for ranges and general specs as to how well they match SDM3045X.
Have just 1x SDM3045X in stock that may have to become the workshop DMM......
Hoping Notepad will suffice for FW code edits.  :-//

Unknowns
Western SDM3055 use a Caddock divider whereas SDM3045X use passives but China SDM3055X-E not known.....highly suspect same as SDM3045X.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod