MESR-100 ESR meter

[PA0PBZ]

Hi,

This ESR meter has been mentioned in the forum a couple of times, but I have not seen a teardown of it yet, so here goes...

It is another basic ESR meter, available on eBay and some other sites for around $59.00. It is powered by a 9 volt battery, which was included (a powerful cell, yeah!) together with some basic test leads.



Current draw when switched on is about 17mA (backlight on), double that when actually measuring.
It has 3 manual ranges (0-1R, 0-10R and 0-100R) and one auto range. I have yet to find out why I would use a manual range, the auto range is fast enough (<2s).

It looks like the design idea was to solder the banana jacks directly on the PCB, probably for another type of case. It just doesn't work with this one, so they just soldered wires.



It's a basic design with a PIC16F886, a LMV824 op-amp and support circuitry



On the bottom of the PCB there is just a LM340 and a 20cm wire to bridge a 1/10" jumper... Don't ask. 
(Yes, I removed the wire. At first I thought is was resistance wire, so I measured it but it came out at 0.02 ohms. Since the accuracy is still ok who knows...)



Accuracy seems ok, a 100R 1% resistor:



And a 0.15R 5% one:



And of course the (very obvious bad) 1000u/16V cap:



It measures using a 100KHz square wave with an amplitude of about 400mV. I've been using it a few times and it picks out the bad caps ok, also in circuit.

[Salas]

Needed one and got one too. This one is balanced for price and form factor between the very few models offered worldwide and does the deed. I attach a picture of its test signal. 100Hz also for large PSU caps would be welcome although no such meter seems to have it. The posts could be made to accept shrouded multimeter leads beyond naked banana plugs it would be convenient. All ESR meters on offer are expensive for just doing a single thing on a single frequency while built in semi-pro quality in my opinion. A market thing, they are not produced in high volumes from major brands as other gear and their dealers are few. If not having an expensive LCR meter with ESR capability they are the only way to go nonetheless.

[Lightages]

The long wire in a coil could have been a way to trim the accuracy on some values as it could have been acting as an inductor. I would not have removed it. Why would they put it there unless they thought it was needed?

[Fraser]

I Just purchased a new improved Mk2 version of this meter. It looks reasonable and has a decent display. Testing will show whether it has decent accurancy though.

http://www.ebay.co.uk/itm/360643330408?var=630113916367&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

GBP37 delivered to the UK

Range is claimed to be 0.001R to 100R which, if true is pretty good at the low end for such a device. Vtest is 0.15V which means it is OK for in circuit testing as it will not be biasing semiconductors on.

Quoted differences between Mk1 and Mk2 versions are below: (buy the Mk2 !)

"Compare MESR100 old V1 and new V2 Improvement:

1)     Change square wave to sine wave 100 KHz, reduce square wave’s high frequency component, and affect the reading passing the test leads and capacitor.

2)     Higher Resolution up to 0.001 ohm.

3)     128X64 dot matrix LCD, with more larger value display and information

4)     Embedded 25V capacitor table at LCD, auto display the capacitor is good or bad reference to common 25V electrolytic capacitor.

5)     New plastic case, curve design for hand carrying. New stand for 60 degree stand on desk.

6)     Use 2X AA battery, more convenience and longer battery life than 9V battery.

7)     Support external USB power, using standard micro-USB port."

[Salas]

The new form factor is seriously better, I don't know about the sinewave effect and just the 25V reference usefulness when lacking the quick look up printed chart though. On a test for a Panasonic FC lytic I had handy the previous version gave me 0.21R and that was spot on agreeing with its datasheet 100kHz spec. It also picked up non bulged but bad caps on a DVD's SMPS in circuit alright. Let us know your hands on impressions when you will get the V2.

[Fraser]

The interior pictures, and my comments on the new MESR-100 V2 may be found in this new thread:

https://www.eevblog.com/forum/testgear/new-esr-meter-mesr-100-v2-by-'jingyan'/msg231614/#msg231614

[Bryan]

I have the v1.0 and can not get it to zero on the 1-10r range. It will zero on the display, but when measuring a cap always gives a negative number 

[Fraser]

Forgive the possibly daft question but are you remembering to short the probes/socket when doing the zero adjustment ?

If you are, then I suggest an email to the supplier as they will likely provide an exchange unit for you.  Does yours have the resistance 'compensation' wire fitted as per the pictures earlier I this thread ?

[Bryan]

Yes shorted with a  piece of short wire. It will zero on the 0-1, or the 10-100 but not on the 1-10, I think a consistent -0.08 . I took it apart  and there is a lengthy piece of wire as in the picture. just as a test, will unsolder and see if it makes a difference, perhaps the wire is too long or not short enough, or maybe has nothing to do with the compensation. Ebay purchase awhile back so doubt I have a recourse now, was purchased a couple months ago.

Maybe the large cap inside has a high ESR 

[2e0eow]

Hi there Bryan, I know this topic is old now, but I thought I'd give it a try. I have exactly the same problem (giving a negative reading) with my mesr-100 V1. Did you ever find out what the problem was?