Internal resistance tester

[IBScootn]

Doctorbass, thanks - i'll get those probes.

[999zip999]

Just order those probes 10 for 4.56usd. shipped. Waiting for the tester.

[Gregb]

why not just use a diode bridge to protect your meter or put a diode in series with the lead until you have checked it??

[Doctorbass]

why not just use a diode bridge to protect your meter or put a diode in series with the lead until you have checked it??

Because it will false the voltage reading. A diode take 0.4V to 0.7V forward when connected in serie so the Ri measurement will be false.

and a diode in parallel will also make it to break in case of reverse polarity due to the low reverse voltage still passing..

This device is sensitive to reverse low voltage

Doc

[999zip999]

I got my tester 2/16. I'm trying it on my konion cells. I get 15.3- 19 for most then a row at 24-25 then a couple at 30 and 35. Does this sound right for konion cells ? what's the cut off point ? I haven't got the pogo points yet.

[texaspyro]

I haven't got the pogo points yet.

Just short the meter probes together to get a "tare" reading. Subtract this from the cell readings to get a more accurate cell reading.

[999zip999]

I'm getting 15.2- 21 on my meter with some 23 and up where should I stop on the upper limit to match the low res. cells ? What are the readings other people are getting on there konion cells ? What are the I.R. limit ?

[Doctorbass]

I haven't got the pogo points yet.

Just short the meter probes together to get a "tare" reading. Subtract this from the cell readings to get a more accurate cell reading.

Yes.. thats what i was doing with the mon 4 wire version tester. May ai suggest to short the probe but not together... It is better to short them by puting them against the same cell tab

By that way you get the contact loss substraction with better accuracy since they are touching the same material and the probe to cell interface is the same . probe to probe would be less accurate.


So make your zeroing by puting both probe on the same cell tab.


Doc

[999zip999]

I got the pogo points today they are very small. Smaller than the tip of a ball point pen, a flat sewing pin. I guess there is no real load on the pins. Will hook up tonite. But dislike cutting open the probes. Could I lenghten the wires 6in. without ill effects ?

[Teh Stork]

I'm getting 15.2- 21 on my meter with some 23 and up where should I stop on the upper limit to match the low res. cells ? What are the readings other people are getting on there konion cells ? What are the I.R. limit ?

Seems like you've got some good konions, mine vary from 25 to 40 (single cell measuring). Shorting the meter - through a tab - mine reads 3.3mOhm. Biggest cap I've got (1.5 farad audio stuff) measured in at 9.9 mOhm.

When trying to measure small smd ceramic capacitors - I can not get a reading. Anyone with a nifty explanation? They do work, my capacitance meter measures them as 0.8uF to 1.1uF...

[999zip999]

Can I add 6in. of wire between the pogo points ?

[Doctorbass]

Can I add 6in. of wire between the pogo points ?

yes

You should have two pogo for the current flow and two for the voltage sense. each of these 4 pogo pins can have 1km wire, it doesn't mater since the wire that will measure have no real current flow thru them... only the two wire with the current will

Search on the forum for kelvin connections or kelvin measurement


Doc

[Kin]

So, I think Doc said this wasn't a particularly sophisticated IR tester design. I was trying to figure out- how does it work? It is simply a resistor and voltmeter setup [I'm not sure with two leads how it would put something in both series and paralleled, but yeah). Just wondering if anyone had a quick explanation.

I am very curious to buy, but also hesitant because $40 is not inconsequential, so I could as well use two voltmeters and my .5ohm 50w resistor for mediocre testing of some mediocre cells (not as important bc i expect IR to be relatively high compared to your good cells). I would need to use a spreadsheet and put in two measurements instead of one, but it would at least get me the information into a spreadsheet anyway (for eventual matching).

[999zip999]

I put the pogo points on and my first test of 17 is now 14, what ? So have 330 cells to go thru. I don't care if my tester reads low as Doc thread say's 30mill. Will help me group for matching better than i had before.

[IBScootn]

So, I think Doc said this wasn't a particularly sophisticated IR tester design. I was trying to figure out- how does it work? It is simply a resistor and voltmeter setup [I'm not sure with two leads how it would put something in both series and paralleled, but yeah). Just wondering if anyone had a quick explanation.

Kin, read this re 4-wire measurement:
http://www.cirris.com/testing/resistance/fourwire.html

[999zip999]

You can heat up the probes with a heat gun and pull the tip out to get too the 2 wires. So the wires are long enough. My reading on the konion cells now at 13.2- 19. and then some out there 30 or 45 and zero volts this one is shot. I think my reading are low on the meter, or I gotten rid of the weak ass cells. I got 50 - 18v3ah packs or 500 cells alot were at just zero, So I'm at 360 ( good ) plus cells now till I match them some more. So going to bulid a 10p 15s then add up to 20s.

[Kin]

So, I think Doc said this wasn't a particularly sophisticated IR tester design. I was trying to figure out- how does it work? It is simply a resistor and voltmeter setup [I'm not sure with two leads how it would put something in both series and paralleled, but yeah). Just wondering if anyone had a quick explanation.

Kin, read this re 4-wire measurement:
http://www.cirris.com/testing/resistance/fourwire.html

Thanks IBScoot. So the tester is providing a current source, which is shorted through the resistor of the battery, and then the voltage across the resistor tells you the voltage of the current source, which in turn tells you the resistors value, given a known value current source? I'm basing my understanding off of the diagram
, but to be honest I'm still not really clear what's going on even if that diagram is properly showing the situation. I'll try to read it again, and then edit this post.

Edit: The explanation seems to be discussing the importance of the fixturing resistance. I'm not totally sure what fixturing resistance is, and I can only guess it's either the contact point between your probe or the tester's own resistance. There is the section "why not just substract fixturing resistance" and it refers to fixturing resistance as something high (2ohm) so I reason that to be the resistor through which an anmeter measures current. Maybe this is part of the "current source" calculation in the previous diagram.
^Actually I wrote this a few times and changed my theory each time. The most notable lesson is just that I don't know remotely enough about electronics.

NEWEST EDIT:
Edit, for what it's worth, I realize my understanding of the diagram is total nonsense. The current source must be the battery. That said, somehow it's describing the voltage across the internal resistance of the battery, which is not physically separable from taking the voltage across the battery terminals. meh meh.

Edit3:
http://en.wikipedia.org/wiki/LCR_meter

[999zip999]

If it just had a red and green light. And all cells where at 4.1v it will still help me.

[Wayne Giles]

Hi,

I saw a limk to this forum from RCG forum (Electric model planes) and noticed this thread.
I make an IR meter as a hobby intended for Lipos as used by aircraft modellers but it will eqally measure LiFe, Lion as well as Lipoly cells just as well.
By coincidence I have just bought 8 x 10Ah Headway Cells for my wife's shopping buggy and thay all measured between 4.6 and 5.4milliohms at 24degC.
It is not a really serious commercial enterprise but it least it breaks even so its a free hobby!

You can see the details with specification at:
http://www.rcgroups.com/forums/showthre ... st20038311
Standard unit measures 2s - 6S lipos (3S - 7S LiFe) either pack or individual cells. You can measure a larger pack in sections and unit is protected against reverse voltage on all inputs.
Although specified for up to 5000mAh for lipos, there is no actual upper limit on capacity of the cells it measures.
I can also add a small mod enabling the unit to measure a stand -alone single cell using an auxilliary supply.

Wayne

[Kin]

Hey, I know this thread is a little old, but I wanted to make some updates for the benefit of anyone looking at the 20R.

I'm using two of the meters at work to measure the impedance of some thermoelectric units that are placed between two matched temperature metal plates (i.e, the thermoelectric peltier modules are minimally generating their own voltage).

i am having trouble with the 20R because i find for the first HOUR that I turn it on, the resistance it measures goes down by 10-15mOhm, on a measurement of 16XXmOhm. Obviously I'm at the limits of what the meter might be able to measure (3mOhm, according to specs, at this resolution), but it's noticeable that the measurements just go down during that hour. The trick is that I haven't been able to isolate if the meters continue changing substantially after that first hour, or if they stay consistent from day to day. They seem to somewhat stabilize.

The bright side is that the meters do offer measurements that are closer to the measurements that the modules supposedly are rated for in China, as compared to our other meter, which is a $300 dollar device without four wire measurement.

I thought people might be curious if they're going to be using this meter to measure a serious set of cells, you might want to do it all in one sitting, and wait for the meter to be on for an hour. If it looks like it stabilizes consistently, I'm going to hard wire it and just perpetually leave it on.

Also, there's a HUGE difference between the resolution levels. So I wonder how that works. For one measurement I might get 1.43ohm and 1658mOhm.