Author Topic: EEVblog 121GW Multimeter Issues (Read 674334 times)

HKJ · « **Reply #875 on:** June 21, 2019, 08:17:09 pm »

Quote from: CDaniel on June 21, 2019, 07:58:59 pm

I don't think is possible , my Fluke 867B is better because Hz ( duty cycle ) is a soft button , you are still in volts mode and you can choose manually a voltage range where works the best . This is how it should be done according to manual .

But 121GW use the rotary switch and has fixed sensitivity , whatever that might be when switched to Hz .

Multimeters basically has two ways to measure frequency and duty cycle:
1) A "logic level" input that supports high frequencies (1+MHz), this usual is based on fairly low voltage levels.
2) Standard voltage input, this is often limited to way below 100kHz, but supports the different voltages ranges.

On the 121GW it supports both frequency and duty-cycle on the logic level input, but only frequency on the standard input.

duodiode62 · « **Reply #876 on:** June 26, 2019, 12:52:11 am »

Hello. I'm having issues with the Low Z function. It doesn't indicate anything at low voltages but seems to work with a very slow update at voltages above about 12. I've put in a issues notification but did not receive a reply. Does any one no of the cure for this error?

Regards, Stuart

Scottjd · « **Reply #877 on:** June 26, 2019, 02:06:06 am »

Hi Stuart,
The manual states the following on page 36:
“The range is not designed to be operated at low voltages (below 12V), it is also not designed for high frequencies. This range is typically used between 50Hz and 400Hz.”
You can download the manual with this link:
https://www.eevblog.com/wp-content/plugins/download-attachments/includes/download.php?id=22499
Hope this helped.

CDaniel · « **Reply #878 on:** June 29, 2019, 07:39:39 pm »

ver2.00 - In millivolt AC range the frequency has a very long persistance if you short the probes or measure something at the sensitivity threshold . In volt AC it is OK . I reported this a long time ago and was resolved ( 1.51 AC mode frequency persistence issue resolved ). I'm too lazy to roll back the firmware , but I'm pretty sure was OK both for volts and millivolts until latest update .

CDaniel · « **Reply #879 on:** June 30, 2019, 08:16:42 am »

Another small issue - the bargraph in millivolt AC with 1KHz low pass filter activated is showing ~50mV less

. In the first picture is sitting at 3 and half , in the second at 3 .

newbrain · « **Reply #880 on:** June 30, 2019, 04:07:23 pm »

Quote from: CDaniel on June 30, 2019, 08:16:42 am

Another small issue - the bargraph in millivolt AC with 1KHz low pass filter activated is showing ~50mV less . In the first picture is sitting at 3 and half , in the second at 3 .

This also might be a regression on 1.51, in the revision history it mentions:

Quote

VAC + LPF bargraph issue resolved.

CDaniel · « **Reply #881 on:** June 30, 2019, 05:15:31 pm »

Yep , that was another issue I reported , but back than it was showing like 10x more with LPF in volts mode , so the bargraph line was allready full at 2V . I don't remember how it was in millivolt range but I would have noticed this issue back then ... Maybe they used some old code in the recent update .

ButterToast1134 · « **Reply #882 on:** July 03, 2019, 03:32:04 am »

So I’ve posted before about this but the Bluetooth radio in my meter isn’t working. My buddy’s meter will connect instantly but mine will not. Using a Bluetooth scanner does not detect the meter at all. This leads me to believe the radio is not functioning. Anyone else have this issue?

Dr. Frank · « **Reply #883 on:** July 03, 2019, 12:02:17 pm »

With FW v2.00, the instrument does not autorange correctly when a DC V between 550.00 and 599.9V (readings on display) is applied.
The DMM switches between the 500V and 600V (1kV) range back and forth w/o finding a stable configuration, and also starts to beep randomly, indicating an overload.

The lower ranges autorange correctly, i.e. down at reading of 5000 counts, up at 55000 counts.

Probably the range switch hysteresis has been corrupted in FW 2.00, as I think this was ok in former versions.

Frank

chronos42 · « **Reply #884 on:** July 03, 2019, 08:30:31 pm »

I can confirm this issue, the range looping starts exactly at 550V DC.

stuartmp · « **Reply #885 on:** July 06, 2019, 09:17:14 am »

Hi All. I just received my 121gw meter on Friday and was playing around with it today and found something that was not working as I expected. It's probably just operator error so I was hoping that someone could possibly explain what's going on.

Ok, I was just doing a basic current measurement. Input voltage is 5v, resistance is a smidge over 300 ohms (300.03). That coupled with the sense and fuse resistance of 1.3ohms should give me a 16.6mA.

So I preformed the measurement and the meter set in DC Auto returns a measured value of 83.55mA in the 500mA range with a burden voltage of 2.6mV. This is obviously incorrect. So I tried the 5A and 10A range. Both of these ranges were correct and returned a value of 16.6mA. So what's going on? Am I doing something wrong? I checked the manual and I must admit that the diagram showing how to measure the current and burden voltage on page 41 is a little confusing it shows no relationship to the power supply and if the load is connected on the high or low side of the common connection. The arrow indicating the current direction is also confusing.

I'll attach some photos which I hope will make things clearer.

I have also installed the v2.0 firmware.

Regards

Stuart

Sent from my SM-G965F using Tapatalk

CDaniel · « **Reply #886 on:** July 06, 2019, 10:53:53 am »

So I don't understand , simply measuring current with 2 leads is showing normally ? Why is -83,53mA like the leads are reversed ? I checked with a 470ohm resistor at 5V and 10V , aprox 10mA and 20mA and the reading is correct in auto range and manual range .

However when using the burden voltage feature , when touching the third lead the reading changes slightly ... is showing aprox 0.1mA more which is pretty weird but not very much .
The circuit is like in your picture (+V) - DUT resistor - current lead and third voltage lead - com lead and power supply ground.

stuartmp · « **Reply #887 on:** July 06, 2019, 11:15:46 am »

Thanks for the response. The leads are not reversed. See the attached image. Auto range (500) vs (5) not sure what's going on either.

Sent from my SM-G965F using Tapatalk

CDaniel · « **Reply #888 on:** July 06, 2019, 11:20:58 am »

And without the third lead is measuring the same ?
Maybe the 500mA range is not calibrated right ...

stuartmp · « **Reply #889 on:** July 06, 2019, 11:42:27 am »

Doesn't seem to make any difference and having the burden voltage on or off makes no difference either.

Please also tell me does the burden voltage 'on setting' just turn on the display and calculation of the burden voltage or does it do something inside the meter as well?

Sent from my SM-G965F using Tapatalk

CDaniel · « **Reply #890 on:** July 06, 2019, 12:01:19 pm »

I don't think the burden voltage is doing something , just measuring volts and amps in the same time ... but to be sure .
So now it is clear that your meter has a problem with the 500mA range , you should talk to Dave what to do ... maybe you could recalibrate it yourself .

stuartmp · « **Reply #891 on:** July 06, 2019, 12:24:50 pm »

Is it a problem with the 500mA range or could it be the firmware. Is the firmware backwards compatible?

How do I contact Dave about this?

Thanks for trying to help out.

Sent from my SM-G965F using Tapatalk

CDaniel · « **Reply #892 on:** July 06, 2019, 12:38:28 pm »

The meter has firmware and calibration data ... if the calibration is corrupt the firmware update won't help , but you can try . Yes the firmware is backwards compatible .
I don't know the procedure , if you bought the meter from him you might have a phone number , if not , an email or you can send him a message using the forum .

e0ne199 · « **Reply #893 on:** July 06, 2019, 02:14:01 pm »

has anyone noticed this?
try to turn burden voltage on, set the 121GW to 10A range and measure load current without using its voltage probe
mine on 10A range, the current reading drops about 2mA when the burden voltage is on, but when i turn the burden voltage off, the current reading on 10A range is back to normal again (without 2mA drop)...
no problems with burden voltage turned on or off when i set the meter to 5A or 500mA range

is this a bug or something? please respond, thx

e0ne199 · « **Reply #894 on:** July 06, 2019, 02:26:50 pm »

Quote from: CDaniel on June 30, 2019, 08:16:42 am

Another small issue - the bargraph in millivolt AC with 1KHz low pass filter activated is showing ~50mV less . In the first picture is sitting at 3 and half , in the second at 3 .

i concur that this problem also exists in my 121GW

CDaniel · « **Reply #895 on:** July 06, 2019, 04:02:31 pm »

Quote from: e0ne199 on July 06, 2019, 02:14:01 pm

has anyone noticed this?
try to turn burden voltage on, set the 121GW to 10A range and measure load current without using its voltage probe
mine on 10A range, the current reading drops about 2mA when the burden voltage is on, but when i turn the burden voltage off, the current reading on 10A range is back to normal again (without 2mA drop)...
no problems with burden voltage turned on or off when i set the meter to 5A or 500mA range

is this a bug or something? please respond, thx

I don't see this particular issue clearly , but may be explicable ... with the voltage probe inserted and burden turn on is picking up the electrical field noise which somehow interfere with the current reading . So when I touched the voltage probe tip from 930mA the reading went to 990mA . Pretty insane .
Even that non zero current offset when you don't measure anything changes when you put the hands near the terminals ...

stuartmp · « **Reply #896 on:** July 07, 2019, 01:50:29 am »

Quote from: CDaniel on July 06, 2019, 12:38:28 pm

The meter has firmware and calibration data ... if the calibration is corrupt the firmware update won't help , but you can try . Yes the firmware is backwards compatible .
I don't know the procedure , if you bought the meter from him you might have a phone number , if not , an email or you can send him a message using the forum .

I have an update. I tried updating the firmware. I managed to downgrade it but it did not fix the problem.

I then tried removing all the leads and then turned on the meter to the A / mA selection. The display shows -100.19 mA when the 500mA scale is selected. All other ranges it shows zero. So I had an idea. I used the relative button to zero the display. I then plug in the leads and to my surprise it reads correctly. So there is obviously a problem with the offset for the 500mA scale. Is there a way to reset this?

Sent from my SM-G965F using Tapatalk

IanB · « **Reply #897 on:** July 07, 2019, 01:56:44 am »

Quote from: stuartmp on July 07, 2019, 01:50:29 am

I then tried removing all the leads and then turned on the meter to the A / mA selection. The display shows -100.19 mA when the 500mA scale is selected. All other ranges it shows zero. So I had an idea. I used the relative button to zero the display. I then plug in the leads and to my surprise it reads correctly. So there is obviously a problem with the offset for the 500mA scale. Is there a way to reset this?

Did you accidentally put the meter in calibration mode and change the zero offset?

stuartmp · « **Reply #898 on:** July 07, 2019, 02:13:06 am »

I just read up on that. No I barely used the meter. I think its time to speak to someone at eevblog. I does appear that somehow the dc offset calibration has been affected by something. [emoji25]

Sent from my SM-G965F using Tapatalk

CDaniel · « **Reply #899 on:** July 07, 2019, 04:05:40 am »

You can try a zero offset callibration for that range as described in the manual . I did that myself for current offsets ( obvious not that bad that yours )


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Author Topic: EEVblog 121GW Multimeter Issues (Read 674334 times)

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