UNI-T UT61E Multimeter teardown photos.

[mariush]

Make sure the infrared led actually works on the meter (use a digital camera or something which will show on the lcd the infrared). It should be fine.

Some of those cheap dongles use Prolific serial-to-usb chip CLONES ... the driver that windows loads detects they're clone chips or chips with the invalid prolific signature and will not work properly.

In your case, I would make sure the connectors are actually soldered properly on the pcb - the solder is often really bad on those.

[Benik3]

It's strange that you didn't measured any voltage, because Logic 0 is high voltage, sou you should measure the max voltage at least on TX pin...

[Nuno_pt]

Hi,

Has anyone see or try this mod for adding new functions ( http://mjlorton.com/forum/index.php?topic=285.0 ), and also this mod for external Vref from this Chinese forum ( http://forum.eepw.com.cn/thread/239953/1 ).

On another topic ( https://www.eevblog.com/forum/testgear/ut61e-drift-and-recalibration/15/ ) about the UT-61e stephenlm324 already did the external Vref mod along with replacing VR1 (2K pot) by 2 x resistors and 50Ohm pot and claims better accuracy and stability( page 2, post 18 ).

Amazing DMM.

[lagman]

Make sure the infrared led actually works on the meter (use a digital camera or something which will show on the lcd the infrared). It should be fine.

Some of those cheap dongles use Prolific serial-to-usb chip CLONES ... the driver that windows loads detects they're clone chips or chips with the invalid prolific signature and will not work properly.

In your case, I would make sure the connectors are actually soldered properly on the pcb - the solder is often really bad on those.

Thanks for your reply. It took me a long time to test the DMM again as I was busy last week.

I checked that the IR led is working and it is blinking at about 2Hz. So I guess it works.

I tried different drivers but nothing seem to work...

I'm under Windows 7 64 bits and in device manager everything seems fine. The device is detected correctly and it created a virtual serial port (COM3). But when I try to connect to COM3 in the Uni-T software it does nothing. I also tried with UltraDMM but got the same results.

I'll now investigate the adapter itself to make sure there is no bad connection... But I'm quite desperate right now.

Thanks for your help!

[lagman]

This is weird...
I got it to work, I don't know how. Then I restarted windows without touching the DMM or the serial adapter and now it doesn't work anymore.
This looks like it's either a bad solder joint (but I don't think so as I didn't touch anything) or a windows/driver problem.

[Benik3]

Try to open the serial converter and looks what chip is inside and check soldering.

BTW does anyone know, what is inside the serial cable of the DDM?

[Legit-Design]

BTW does anyone know, what is inside the serial cable of the DDM?

https://youtu.be/A8m_Os3OPhA?t=2m17s
2m17s starts about the adapter.

[lagman]

I can't check what the chip of the USB to RS232 adapter is as it's below a black blob.

[lagman]

This is driving me crazy! :S
I checked solder connections and all seem good.
Is it possible to get the chip ID in windows?

[PedroDaGr8]

Try to open the serial converter and looks what chip is inside and check soldering.

BTW does anyone know, what is inside the serial cable of the DDM?

The schematic earlier in this thread has the schematic for the adapter I think.

Sent from my EVO using Tapatalk

[sachleen]

It does, a HE2321U

[lagman]

I ran out of ideas regarding my problem with the RS232 adapter...
I'll give up for now unless you people have other ideas.

Thanks anyway for the help! 

[Rick Law]

I ran out of ideas regarding my problem with the RS232 adapter...
I'll give up for now unless you people have other ideas.

Thanks anyway for the help! 

Lagman,

I suspect it is your RS232-USB convertor.  I had many problems with that when my UT61E was new.  The Rx light on the adaptor even blinks but the program doesn't read.  I tried a few different RS232-USB convertor and finally got a Sabrient with the FTDI chipset.  That cable was expensive ($17).

See this thread I wrote some time back:
https://www.eevblog.com/forum/testgear/ut-61e-rs232-usb-chipset-worked-and-chipset-that-failed/

Also, try to see first if the RS232 cable is working by connecting it to a "real" RS232 com port if you have an older machine with one.   This will rule out your UTE-to-RS232 part being the problem and we can focus on from RS232 to PC part.

Rick

[dr_p]

This is weird...
I got it to work, I don't know how. Then I restarted windows without touching the DMM or the serial adapter and now it doesn't work anymore.
This looks like it's either a bad solder joint (but I don't think so as I didn't touch anything) or a windows/driver problem.

I have major software problems in connecting a OBD scanner for my car. It's USB to Serial, and shows as a COMx in Device Manager, but doesn't really work. As it turns out, Toshiba Bluetooth Stack keeps screwing up the COM ports, somehow. I made it work at some point, but I don't remember how. I used it for some time, all was good, worked every single time. Lost it after a restart (weeks later, because the laptop always went into standby). It's frustrating because I can't remember what the flick I did.

I suspect you might have the same software issues.

I will dig more into how COM ports are managed on a modern PC and possible causes for other people's (unrelated) equipment not working on serial-over-USB.

[lagman]

Thanks for your reply. I'll take a look into other RS232 to USB converters.

[SeanB]

Bit of a sledgehalmmer approach is to install Virtualbox and the addons and let it handle the USB device. That way you can have very fine control as to which USB device is assigned and the driver it uses.

[Dareksa]

Lagman, I have this kind of adapter http://allegro.pl/te7-adapter-usb-na-rs-232-com-pl-2303-prolific-i3876718203.html and it working without problems with my UT61E.
You only have to set com port to port 1-3 in device manager.

[lagman]

Thanks for the link.

[iloveelectronics]

Based on my experience, Prolific based converters could be problematic. FTDI based ones seem to be much less likely to have issues on most PC's, though more expensive.

[lpc32]

There's also SiLabs. The CP2102 is common. Don't know how it is, but it costs closer to the Prolifics and I think all versions should have drivers for Windows 8.

[Dareksa]

You are right that the FTDI can be less problematic than other chips, but this Prolific converter works for me with each of my equipment.
Does not matter if I have to configure cisco switch, LPG in the car or connect UT61E to PC.

[uski]

Not sure if this has been posted already :


Of course you don't have to work with 2500V to encounter such transient voltages.
Measuring the voltage across a relay coil might be enough if there is no free-wheel diode.
It can also happen with AC circuits if there is a motor, or in a car sometimes.

Any idea as to suitable MOVs or spark-gaps for a UT61E ?
Something that will allow 400VAC measurement safely but trigger at, say, 1000VAC ?

[SeanB]

I added 2 275VAC VDR's in series in the 2 places on the PCB in mine. Works well enough to measure 250VAC, but will now clamp at 793V for overload. Just went and tested now with a high voltage source that goes to 1400V. The VDR's were the 5mm type from RS. I needed one, but the SSM is 5, so there were 4 spare and they were placed in the UT61E.

Bought both the UT61E and the Dy294 green lunchbox transistor/capacitor tester from Frankie ( Iloveelectronics).

[Wytnucls]

I haven't seen the Max Min modification done on the UT61E anywhere yet. So here it is:

Bridging pin 100 and 98 on the Cyrustek IC will disable the REL mode and enable the Max/Min mode, which I find more useful.
Be careful with the soldering, as the pins are very close to each other. It isn't necessary to cut any traces and the mod is reversible at any time.
Max Min works with most meter selections.

[lagman]

I'm trying to measure the frequency and duty cycle of a flashlight which uses PWM to control light intensity.
I set my DMM using the 10A slot  on the A range:

And put the meter in series (like I would do to measure the amp draw).
I get no readings either for duty cycle or frequency.
Am I doing something wrong? Thanks.