DE-5000 LCR TL-21 mod.

[McBryce]

Hi all,
    I got a DER EE DE-5000 (also sold as IET) LCR meter a while back. It came with a TL-21 connector that looks like this: http://www.japaninabox.jp/wp/wp-content/uploads/2013/08/der-ee-de-5000-high-accuracy-andheld-lcr-meter-with-tl21-tl22-tl23-iet-06.jpg
The problem is, the crocodile clips are crap. They're pretty cheap, don't grip the components pins particularly good and the wires are so short that they can be difficult to connect at all to some parts. My plan is to remove them and install 4 banana sockets so that I can use my standard Kelvin clips with it. Has anyone tried this yet? Is there enough space in the case for sockets? And is there any disadvantages to doing this? The meter is taking a 4-wire measurement, but the 4 wires actually connect at the base of the crocodile clip at the moment, so using proper Kelvin clips should actually give a more accurate reading.

McBryce.

[Lightages]

I modified mine. I purchased some cheap Kelvin clips on ebay, cut off the ends,and soldered the cables directly to the board in place of the cheap aligator clips.

[ManateeMafia]

I was going to do the same thing with mine. I bought a spare tweezer set so that I could replace it if it breaks (again). I think the price was about the same.

 I was planning on using Mueller kelvin clips that I had as spares. I already bought the Extech LCR205 smt adapter for it too, but the blades of the adapter aren't quite long enough for a secure fit.

[McBryce]

I'd prefer not to solder the Kelvin clips onto the TL-21 as I use them on other meters too. I'll have to investigate the smallest 4mm sockets I can get and see if I can fit four of them into the case.

McBryce.

[Lightages]

It is cheaper, easier, and better IMHO to just buy these and solder them in:
http://www.ebay.com/itm/LCR-Meter-Test-Leads-Clip-Kelvin-Wires-With-2-BNC-per-Channel-Red-Black-/171907327574?hash=item280679a656:g:eLIAAOxyhXRTO-7i

[McBryce]

Yes, it's probably easier, but I doubt it's cheaper. It also means that the TL-21 then becomes a case with bulky leads (and I already have way too many leads around the room). With sockets it becomes a tidy little box and I just use the leads I already have. I've just ordered the smallest sockets I could find (for €5). I'll see if they fit when they get here.

McBryce.

[PedroDaGr8]

Yes, it's probably easier, but I doubt it's cheaper. It also means that the TL-21 then becomes a case with bulky leads (and I already have way too many leads around the room). With sockets it becomes a tidy little box and I just use the leads I already have. I've just ordered the smallest sockets I could find (for €5). I'll see if they fit when they get here.

McBryce.

Don't forget this is a 5-wire connection, not a 4-wire connection. If you break the kelvin leads out into their individual lines you are supposed to have a guard shield around the lines too. Even the short alligator leads use shielded cable (with all of the shields connected together to the guard pin). This supposedly becomes even more important at longer lengths.

You can see the shielding here (the braided copper) soldered to the guard-line:

[Fat]

Here are mine made from an Ebay kelvin set with a BNC end.

[TimFox]

I bought two extra TL-21's to make fixtures.
On one, I replaced the two black cables with two teflon shielded twisted pair cables to Kelvin clips, roughly 60 cm long.
On the other, I replaced the black cables with four RG-174 coax cables to BNC plugs, to allow making "black box" fixtures with binding posts at different spacings.
In the black-box fixtures, I included a small switch to short the binding posts together for short-circuit calibration, using multiple-pole miniature toggles to reduce the contact resistance.
I kept the original TL-21:  I haven't had any problems with the alligators except that the plastic covers make them stiff.
I'm looking for a good way to keep the alligators the correct distance apart (corresponding to the final spacing on the component) when doing the open-circuit calibration.

[circuitravi]

what is the good kelvin clip?



OR



one type has 2 wire connect to both kelvin clip end and other type 2 wire connect to one end.

[TheSteve]

They are both connected the same. The cables in the second picture loop around to the other side of the clip near the hinge.

[McBryce]

Yes, it's probably easier, but I doubt it's cheaper. It also means that the TL-21 then becomes a case with bulky leads (and I already have way too many leads around the room). With sockets it becomes a tidy little box and I just use the leads I already have. I've just ordered the smallest sockets I could find (for €5). I'll see if they fit when they get here.

McBryce.

Don't forget this is a 5-wire connection, not a 4-wire connection. If you break the kelvin leads out into their individual lines you are supposed to have a guard shield around the lines too. Even the short alligator leads use shielded cable (with all of the shields connected together to the guard pin). This supposedly becomes even more important at longer lengths.

You can see the shielding here (the braided copper) soldered to the guard-line:

Yes, I was aware of the guard connection, but I intended leaving that unconnected as my Kelvin clips (like the mods shown above) don't contain an additional shield anyway. Lots of ideas to go on though now, thanks for all the ideas and pics. I'll post a picture of what I've done when it's finished.

McBryce.

[Carrington]

Another DE-5000 LCR mod. 
http://designideas.cocolog-nifty.com/blog/2014/09/de-5000-test-fi.html

[McBryce]

A bit more than I actually need, but thanks for the link. Still waiting for the 4mm sockets to arrive before I start my mod.

McBryce.

[mos6502]

Waitaminute ... so there's a PCB with SMD pads in the TL21 that's covered with this sticker? Why didn't they leave it exposed?

I think I'll have to take a knife to mine ...

[Lightages]

So that it is what the circuit board is for! The problem is, as built, it stil can't do anything without soldering some wires to it. his would also render the external test connections less accurate as the circuit board would be adding its capacitance and inductance to the reading.

[mos6502]

  You're right, one would probably want to remove the PCB to which the wires are attached, hook up the SMD PCB to the blade contacts and make a dedicated TL-21 for SMD devices.

On closer inspection, the SMD pads don't have a Kelvin connection either ... 

[McBryce]

...and make a dedicated TL-21 for SMD devices.

You mean like the TL-22 ?

McBryce.

[mos6502]

...and make a dedicated TL-21 for SMD devices.

You mean like the TL-22 ?

McBryce.

The tweezers aren't that great. I have them. The tips are not very precise (cheap stamped metal) and the thick cable is clumsy. Putting SMD components directly on a PCB would work better, IMHO. It's really odd that they would go to the lengths to manufacture those PCBs but then not hook them up and hide them under a sticker.

[McBryce]

Yes, I have a TL-22 myself. It does the job more or less, but it's galaxies away from winning any prizes for design or usability. The manufacturing quality is relatively good, it's just a bad design.

But back to the TL-21. I've opened mine and the PCB under the lid on mine is a non-etched PCB. So there seems to be different versions. See below.
The sockets arrived. They were the smallest 4mm shrouded sockets I could find, but there's not a chance I can get 4 of them on the case, so I'll have to come up with some other solution 

McBryce.

[Lightages]

The sockets arrived. They were the smallest 4mm shrouded sockets I could find, but there's not a chance I can get 4 of them on the case, so I'll have to come up with some other solution 

McBryce.

This is why I suggested buying another set of Kelvin leads and just soldering them directly. It is the surest and cheapest solution.

[electr_peter]

I modified TL-21 adapter as well, see my post broken-der-de-5000-tl-21-crocodile-clip-adapter
TL-21 has tendency to break internal solder joints - I had to repair it.

[markce]

Also please have a look here:

https://www.eevblog.com/forum/testgear/der-ee-de-5000-lcr-meter-with-changeable-cables/

[Corner]

Yes, it's probably easier, but I doubt it's cheaper. It also means that the TL-21 then becomes a case with bulky leads (and I already have way too many leads around the room). With sockets it becomes a tidy little box and I just use the leads I already have. I've just ordered the smallest sockets I could find (for €5). I'll see if they fit when they get here.

McBryce.

Don't forget this is a 5-wire connection, not a 4-wire connection. If you break the kelvin leads out into their individual lines you are supposed to have a guard shield around the lines too. Even the short alligator leads use shielded cable (with all of the shields connected together to the guard pin). This supposedly becomes even more important at longer lengths.

You can see the shielding here (the braided copper) soldered to the guard-line:

Yes, I was aware of the guard connection, but I intended leaving that unconnected as my Kelvin clips (like the mods shown above) don't contain an additional shield anyway. Lots of ideas to go on though now, thanks for all the ideas and pics. I'll post a picture of what I've done when it's finished.

McBryce.

Hi McBryce, did you manage to get yours to work perfectly? I have these leads I hand made a while ago. Each wire is just 14AWG stranded wire. I cut the plug ends off only to realise I also need a guard wire to connect onto the TL21... I should have checked these threads first before I sacrificed a pair of leads.

I assume that I can't easily mod my existing leads to have a guard wire. Can I safely leave the guard wire out and only connect 4 wires to TL21? Would this affect measurements, say for small resistors and capacitors?

Edit: Attach photo

[McBryce]

Hi Corner,
     in the end I used shielded Kelvin clips with 4x BNC connectors. I 3D printed a new housing to put it all into. This is what it looks like. The measurements with this are identical to the values I get with the original short clips.

McBryce.