I think Joe will reveal the real issues with this meter once and for all. He has planned a number of vids and will be running one on firmware version differences. Facts and data are always appreciated along with his unbiased assessment.
Might put an end to the fanboy and troll comments this meter seems to attract?
Joe
The rotary switch contact holder has a 3 split shaft with little tangs that grab the back of the PCB. The height of these tabs minus the PCB thickness was probably what determined the compression of the contacts in the original design.
I think the idea of the shim was to provide more compression without having to remold the plastic contact holder.
You didn't measure the height of the tabs, but since the shim is still present one can conclude that the new meters ae same as old except with shim pre-installed.
The shim is not necessarily a bad idea, although a tolerance analysis of the resulting stack-up would surely prove otherwise, but maybe proper height tabs caused too much friction and subsequent debris or since the contact load is in a straight line perhaps the assembly would cock off axis which the shim would prevent.
The materials and the optimal contact preasure for long life shouldn't be "rocket sience" if you are in the industry , but ... when we see how difficult it is for them to do a decent firmware the trust is not very high .
I wrote this before several month:
"A 220pF NP0 ceramic capacitor is shown as 0.160nF at the first time, after switching off and on again as 0.180nF, after another power cycling as 0.200nF... The more often I switch the meter off and on, the closer the reading comes to the actual value. Also if I first use a small capacity, then a bigger one (e.g. several hundred nF) and then again the small capacity, the 121GW every time shows a different reading. I am not able to get a steady reading of small capacities with the 121GW."
This is one of the most weird issue I have ever seen with a multimeter. The fact that Joe's prototype seems not affected from this issue shows that this probably can't be fixed with a firmware update and is hardware related.
I think Joe will reveal the real issues with this meter once and for all. He has planned a number of vids and will be running one on firmware version differences. Facts and data are always appreciated along with his unbiased assessment.
Might put an end to the fanboy and troll comments this meter seems to attract?
That's a tall order!!
I wouldn't read too much into the unboxing video beyond that it does appear that the mechanical stack up between the prototype and production meters appears the same (except for the added preload caused by the shim). Not being able to read the 150pF was a bit of a surprise but I am sure I could add enough capacitance to the fixture to get the meter to read something, then null it out and try again. It's not like we have not seen this with other meters but I wouldn't have expected the 121 to be this far out.
I don't recall the prototype ever having problems reading a 1M resistor. Actually, I don't think I have seen ANY meter exhibiting a problem like this. After cycling the switch a few times, the readings continued to get tighter and I never saw the meter hunt like that again. It can be difficult to track down problems like this that are not reproducible.
Obviously the settling time has been a hot topic. I'm sure a few of you remember me posting a fair amount of data on the firmware changes to the filters which I expect was an attempt to get the meter to settle faster. I removed most of that data to help clean up the "issues" area. Personally, I will take slow, accurate measurements any day over fast inaccurate ones. While I had installed 1.57 in the prototype, I don't appear to have any notes about testing it. I suspect the upgrade was part of sorting out the BLE / LabView interface.
My plan is to dedicate one full segment just to the firmware. I plan to repeat my previous noise testing on the production meter which will include all the same firmware plus the latest versions. For now I will stay focused on the hardware differences between the current production meters and the prototype.
if it cannot measure pF then it will be useless for me... and if firmware update cannot fix this issue then looks like i need to sell my 121GW...seeing that even chinese cheap crap multimeters can measure pF range accurately really makes 121GW look like a stupid purchase
Maybe Dave can advise us all on what the current revision is for the meters and if he plans to sell a revised PCB to those who already have the meter?
A discounted replacement PCB for early adopters would be much appreciated! (Providing its actually an improvement of course).
Maybe Dave can advise us all on what the current revision is for the meters and if he plans to sell a revised PCB to those who already have the meter?
A discounted replacement PCB for early adopters would be much appreciated! (Providing its actually an improvement of course).
No plans for replacement boards to be made available, there is no functional difference, it's just a normal process of refining the design over time, happens regularly to all meters. Existing customers are not missing out on anything.
I brought this up when I bought my 121 GW and was steam rolled by the same people moaning now that the meter was great and upgrades meant nothing and the meter I got was the same as the revised ones so no different. In fact it wasn't new so it was no different yada yada yada....!
Too funny
Maybe Dave can advise us all on what the current revision is for the meters and if he plans to sell a revised PCB to those who already have the meter?
A discounted replacement PCB for early adopters would be much appreciated! (Providing its actually an improvement of course).
No plans for replacement boards to be made available, there is no functional difference, it's just a normal process of refining the design over time, happens regularly to all meters. Existing customers are not missing out on anything.
Hey Dave it would be nice if you could provide an update on what hardware revisions the "most current" version of the 121GW has had installed.
It would also be appreciated to know what the revised hardware has been fitted to achieve in the meter's function or protection.
It seems the EEVBLog store is selling older versions of the 121GW meter as Joe Smith found with his latest purchase of 2 new meters from your store. Can you supply from your store the current version meter? Will you discount the old meters or continue to sell old revision meters at full price?
How about sending Joe Smith 2 current version meters so we can see the results of comprehensive and unbiased testing of the current 121GW meter!!!!!!!!!!!!!!!!!!!