Author Topic: EEVBlog 121GW Discussion thread  (Read 195810 times)

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Offline dadler

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Re: EEVBlog 121GW Discussion thread
« Reply #1575 on: June 11, 2019, 03:29:52 pm »
hello i have a question...
does 121GW multimeter have differential probe for measuring current? i want to measure current around more than 10 Amps on my device anyway
answer is really appreciated, thx before

A differential probe for... current? What is your use case?

Without more information or your requirements (AC or DC? Contactless or resistive current measurement? Are the sources isolated?), the following methods may work.

Multiple 121GW meters can connect to an Android device or Windows PC via Bluetooth, and math functions can be performed against the connected meters. You could simply take the subtraction of the readings between two connected meters.

Resistive:
  • 2x 121GW meters (or any oscilloscope with simple math functions + some milliohm-scale power resistors)
  • An Android device or Windows PC (if using the 121GW)
Contactless:
  • 2x 121GW meters (or any oscilloscope with simple math functions)
  • 2x hall-effect current sensors, such as the PDI CA-60
  • An Android device or Windows PC (if using the 121GW)

It may be more cost-effective (and offer greater insight) to use a cheap oscilloscope such as a Rigol DS1054Z than multiple 121GW meters. Depending on your requirements, you could also build a circuit to do this, and measure it with a single 121GW (or any other meter or oscilloscope).

But answer the specifically asked question: no, the 121GW doesn't have any differential probes.
« Last Edit: June 11, 2019, 08:28:15 pm by dadler »
 

Offline exe

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Re: EEVBlog 121GW Discussion thread
« Reply #1576 on: June 11, 2019, 09:30:36 pm »
Afaik all DMMs are "differential" in a sense they are not referenced to ground.

As of measuring larger current, just use an external shunt.
 

Offline beanflying

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Re: EEVBlog 121GW Discussion thread
« Reply #1577 on: June 11, 2019, 10:38:15 pm »
So the TV options sucked tonight. On the printer but I am off to bed at 10.30pm so we will see what the morning brings. I may have made the press section to strong to push in so it might take a tweak yet.

Printed heavy and on it's side with supports to get the layer orientation correct for strength. If it looks ok I will swing 4 or 5kg extra on mine to test before releasing the final design. Add your own magnet, webbing or a lump of old rope....



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Offline beanflying

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Re: EEVBlog 121GW Discussion thread
« Reply #1578 on: June 12, 2019, 11:50:40 am »
Overall size is nicely snug so the tongue will be gripped by the bumper on all sides. The Push release with PLA isn't and is to stiff. Printed in PETG would be more flexible and tougher but I am aiming for a PLA printable with 0.2mm layers so all 3D printers can manage it. Also need to reduce the release length and round it's corners to suit the bumper. It fits in the zip up case installed so even if the release is hard to use not that much of an issue I guess and it can just stay locked in.

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Offline beanflying

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Re: EEVBlog 121GW Discussion thread
« Reply #1579 on: June 12, 2019, 03:10:33 pm »
Tweakage finished unless anyone who makes it finds an issue and I will see if it can be improved.

Hollowed out the release so it now has more flex, fattened up the front bar for more strength and short of hanging your toolbag on it shouldn't ever be a problem. Also increased the web at the rear of the release for more strength when being pressed. The release as it is here in PLA can be deflected down by about 3mm without any risk of breaking it and the urethane section of the bumper can easily be flipped over it then to release the hanger. Still recommend PETG if you have it (I will try one next time I have some loaded).

Print settings 6 layers all round 40% infill so basically solid at 0.2mm layers. Printed on edge with bed supports only, could fully support it but the one shown in this post wasn't. STL is in the Zip file attached here.
Coffee, Food, R/C and electronics nerd in no particular order :)
 
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Offline EEVblog

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Re: EEVBlog 121GW Discussion thread
« Reply #1580 on: June 12, 2019, 04:26:40 pm »
It fits UEI's magnetic hanger, but I don't actually sell that.

This one, I assume:
https://www.ueitest.com/products/accessories/amh1

Yep, I think that's the one.
Could probably make a little slide in adapter that took some sort of standard size magnet (say 10mm dia) and allowed it to fit snug inside.
 

Offline beanflying

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Re: EEVBlog 121GW Discussion thread
« Reply #1581 on: June 12, 2019, 05:18:39 pm »
It fits UEI's magnetic hanger, but I don't actually sell that.

This one, I assume:
https://www.ueitest.com/products/accessories/amh1

Yep, I think that's the one.
Could probably make a little slide in adapter that took some sort of standard size magnet (say 10mm dia) and allowed it to fit snug inside.

Very rough 5 minute hack up to take a 20x10mm 5mm c/sunk magnet. It needs to be this tall to clear the rubber bumper.
Coffee, Food, R/C and electronics nerd in no particular order :)
 
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Offline beanflying

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Re: EEVBlog 121GW Discussion thread
« Reply #1582 on: June 12, 2019, 06:17:47 pm »
And here is a nicer one.

Designed to take a 20x10 5mm Magnet (Order away I have already  ;) ) eBay auction: #183364882157
Countersunk 5mm screw or bolt to suit and the recess will take a Nyloc nut for depth but a standard one and lock washer would do too.

I haven't printed this one but using the settings above should print fine. STL is in the Zip.

Coffee, Food, R/C and electronics nerd in no particular order :)
 

Offline e0ne199

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Re: EEVBlog 121GW Discussion thread
« Reply #1583 on: June 12, 2019, 10:50:59 pm »
hello i have a question...
does 121GW multimeter have differential probe for measuring current? i want to measure current around more than 10 Amps on my device anyway
answer is really appreciated, thx before

A differential probe for... current? What is your use case?

Without more information or your requirements (AC or DC? Contactless or resistive current measurement? Are the sources isolated?), the following methods may work.

Multiple 121GW meters can connect to an Android device or Windows PC via Bluetooth, and math functions can be performed against the connected meters. You could simply take the subtraction of the readings between two connected meters.

Resistive:
  • 2x 121GW meters (or any oscilloscope with simple math functions + some milliohm-scale power resistors)
  • An Android device or Windows PC (if using the 121GW)
Contactless:
  • 2x 121GW meters (or any oscilloscope with simple math functions)
  • 2x hall-effect current sensors, such as the PDI CA-60
  • An Android device or Windows PC (if using the 121GW)

It may be more cost-effective (and offer greater insight) to use a cheap oscilloscope such as a Rigol DS1054Z than multiple 121GW meters. Depending on your requirements, you could also build a circuit to do this, and measure it with a single 121GW (or any other meter or oscilloscope).

But answer the specifically asked question: no, the 121GW doesn't have any differential probes.

haha i asked a wrong question i think...i mean external current probe clamp for 121GW that can measure current more than 10 amps, i am sorry i thought when i mentioned differential probe that would mean external current probe clamp  ;D

maybe i need to repeat the question again..does 121GW have external current probe clamp for measuring high current (more than 10 amps)?
 

Offline lowimpedance

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Re: EEVBlog 121GW Discussion thread
« Reply #1584 on: June 17, 2019, 04:22:18 pm »
Tweakage finished unless anyone who makes it finds an issue and I will see if it can be improved.

Hollowed out the release so it now has more flex, fattened up the front bar for more strength and short of hanging your toolbag on it shouldn't ever be a problem. Also increased the web at the rear of the release for more strength when being pressed. The release as it is here in PLA can be deflected down by about 3mm without any risk of breaking it and the urethane section of the bumper can easily be flipped over it then to release the hanger. Still recommend PETG if you have it (I will try one next time I have some loaded).

Print settings 6 layers all round 40% infill so basically solid at 0.2mm layers. Printed on edge with bed supports only, could fully support it but the one shown in this post wasn't. STL is in the Zip file attached here.

 I have printed your design using ABS, and it was completely successful with no issues so far. As printed the hanger snaps confidently into the slot on the bumper, (support material removed of course!).
The locking tab works perfectly and can be easily depressed for removal from the meter, no structural problems observed after many test operations.
See attached photos using a FLUKE hanger  :D.
 Thanks again for the effort.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 
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Offline frankmhowell

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Re: EEVBlog 121GW Discussion thread
« Reply #1585 on: July 05, 2019, 12:22:43 am »
But what is the metric of the Time field? Is it in interval units (e.g., seconds, etc.) relative to the start time stamp? As successfully received via Bluetooth?
 


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