Got my GDM-8251 from eBay today...one question

[xrunner]

They could've put a resistor between pins 1 and 4 to prevent a complete short circuit when plugged into a real USB port.

But that would have cost an extra few cents per unit. 

[bitseeker]

They could've put a resistor between pins 1 and 4 to prevent a complete short circuit when plugged into a real USB port.

But that would have cost an extra few cents per unit. 

Yeah, I was going to say that, but for the price they're charging, they can afford it.

[sequoia]

Response from GW Instek:

>The issue is caused by dynamic range. For GDM-8255A/8251A, customer need to manual set the range for it.
>The newer model like GDM-834x or GDM-8351 has already solve this issue.

Yep.

I ordered the GDM-01 cal key from Tequipment, but then found out that they couldn't ship it until March 28, so I had to cancel that order. I found the key for sale on Ebay so it should be here in a few days. I also got the firmware file from GW Instek, so I'm ready to try the upgrade as soon as I get the cal key, via the RS-232 serial connection.

Did it take long to get response from GW Instek?  I requested firmware via their "contact us" web form at www.gwinstek.com maybe a week ago but so far no reply...

[xrunner]

Did it take long to get response from GW Instek?  I requested firmware via their "contact us" web form at www.gwinstek.com maybe a week ago but so far no reply...

Only took 24 hours. Here's the email address I wrote to -

services@goodwill.com.tw

[sequoia]

Did it take long to get response from GW Instek?  I requested firmware via their "contact us" web form at www.gwinstek.com maybe a week ago but so far no reply...

Only took 24 hours. Here's the email address I wrote to -

services@goodwill.com.tw

Thanks, that email address worked.  Still waiting to receive some USB connectors I ordered from eBay, so I can make my own "CAL key" with small resistor soldered between pins 1 and 4 inside the connector....

If firmware upgrade is successful, then need to figure out if there would be some place in Southern California to get this thing checked/calibrated at reasonable cost.... (

[xrunner]

Thanks, that email address worked.  Still waiting to receive some USB connectors I ordered from eBay, so I can make my own "CAL key" with small resistor soldered between pins 1 and 4 inside the connector....

Cool!

If firmware upgrade is successful, then need to figure out if there would be some place in Southern California to get this thing checked/calibrated at reasonable cost.... (

If ... if? Of course it will be successful! 

Been using mine quite a bit. As a matter of fact was just using it to monitor the temporary RAM voltage I applied to my HP 3457A while I replaced the backup battery. That's something I did not want to make a mistake on because the ram-(no pun intended)-ifications would have been unpleasant.. 

[sequoia]

Got some USB (type-A) connectors from ebay (10 for $2.35 with free shipping) to make my own "cal key".
First, I soldered 100 ohm resistor across pins 1 and 4, but unit didn't enter calibration mode on boot (simply booted up normally). Next, I tried shorting pins 1 and 4 and that worked!

Firmware upgrade was successful with the home made "cal key"...

[xrunner]

Got some USB (type-A) connectors from ebay (10 for $2.35 with free shipping) to make my own "cal key".
First, I soldered 100 ohm resistor across pins 1 and 4, but unit didn't enter calibration mode on boot (simply booted up normally). Next, I tried shorting pins 1 and 4 and that worked!

10 for $2.35 ... Considering the ridiculous price they are being sold for, you could make a killing selling home made cal keys. 

Firmware upgrade was successful with the home made "cal key"...

 

[BloodyCactus]

Got some USB (type-A) connectors from ebay (10 for $2.35 with free shipping) to make my own "cal key".
First, I soldered 100 ohm resistor across pins 1 and 4, but unit didn't enter calibration mode on boot (simply booted up normally). Next, I tried shorting pins 1 and 4 and that worked!

10 for $2.35 ... Considering the ridiculous price they are being sold for, you could make a killing selling home made cal keys. 

someone must be sitting on a metric tonne of original cal keys because one comes with each unit when its purchased. if all these are hitting ebay with no cal key. someone is hoarding them lol!

[bitseeker]

someone must be sitting on a metric tonne of original cal keys because one comes with each unit when its purchased. if all these are hitting ebay with no cal key. someone is hoarding them lol!

Since the bulk of these units are from the ITT liquidations, someone might have them. But, more likely, they were tossed as extraneous accessories.

[frog7227]

A little bit of a thread hijack here , but here it goes.
After lots of pain with the original GW-Instek DMM Viewer...
I wrote program to communicate with a PC in Java.
At the moment it needs the RXTX library installed system wide.
I've only tried it on Windows, I'll be trying it on Linux later.
I'll offer a .jar version once I've compiled and compressed everything (Including RXTX).
Link: https://github.com/frog7227/SerialInterface
If you have any issues or proposals for features post them on my Github, I'll see them much faster that way  .

[xrunner]

A little bit of a thread hijack here , but here it goes.
After lots of pain with the original GW-Instek DMM Viewer...
I wrote program to communicate with a PC in Java.
At the moment it needs the RXTX library installed system wide.
I've only tried it on Windows, I'll be trying it on Linux later.
I'll offer a .jar version once I've compiled and compressed everything (Including RXTX).
Link: https://github.com/frog7227/SerialInterface
If you have any issues or proposals for features post them on my Github, I'll see them much faster that way  .

Cool - we like that kind of hijacking. 

[CustomEngineerer]

Got some USB (type-A) connectors from ebay (10 for $2.35 with free shipping) to make my own "cal key".
First, I soldered 100 ohm resistor across pins 1 and 4, but unit didn't enter calibration mode on boot (simply booted up normally). Next, I tried shorting pins 1 and 4 and that worked!

Firmware upgrade was successful with the home made "cal key"...

Shorting pins 1 and 4 also worked for me. Had an extra usb connector laying around so copied sequoia's key. Thanks for showing pics.