[Test-Equipment] ESR meter reviews

[Richard Knoppow]

----- Original Message ----- 
From: <bonddaleena at aol.com>
To: <TekScopes at yahoogroups.com>; 
<test-equipment at mailman.qth.net>
Sent: Monday, June 27, 2011 3:07 PM
Subject: [Test-Equipment] ESR meter reviews


>
>
>
> Hi. As a long time ham and restorer of older radios and 
> test equipment, I have always been aware of capacitor 
> failures. This started when I was an Engineer with IBM and 
> did failure analysis on circuit boards. This discussion 
> will focus only on electrolytic caps.
> Since then, I have found 'buckets' full of bad caps in all 
> vintages of equipment.
> I now own 3 quite different ESR meters and thought I'd 
> share the info with you folks. All 3 have good/not so good 
> points.
> First an important caveat that even very experienced techs 
> overlook....
>
> The use of a small, DVM style cap 'tester' will tell you 
> nothing about leakage or ESR. They are great for finding 
> VALUE.
> You can find a comparison of the following meters on the 
> AnaTek website.
>
> My meters:
>
> Mat Electronics Model MUL3333. This was my first ESR 
> meter. It's analog and cheap, er, inexpensive. ha ha
>
> Pros:
> works OK
> inexpensive
>
> Cons:
> scale too compressed at low resistance end
> " makes it difficult to find shorts
>
> Observations:
> I believe this meter got a bum rap in the AnaTek 'review' 
> because of a broken battery contact. I have had no such 
> problems in 2 years.
> The 'overly compressed scale' situation, is easily 
> rectified by putting an inexpensive DVM (with a buzzer 
> function) in parallel with the MUL3333. This easily senses 
> the difference between a short and a low value ESR cap. 
> This does make for a bulky combo.....
>
> Peak ESR 60
>
> This was my second purchase. Kind of a strange shape 
> factor but that doesn't really matter.
>
> Pros:
> Works SUPER
> Gives you cap 'values'  (out of crcuit) + ESR
> Automatically discharges small (!) caps. It won't bleed 
> down your linear amps caps!
>
> Cons:
> Clumsy to use, due to it's need to 'restart' constantly 
> (see Observations for more info)
> Small alligator clips with short leads
> Can't go from cap-to-cap quickly
> High $
>
> Observations:
> At first, I thought the constant need to restart the 
> device was a major disadvantage. However, I have come to 
> learn that in it's 'start up' routine, it checks for 
> charged caps and discharges them,
> I built a small aluminum stand to prop it up for easier 
> viewing.
> I notice Peak has a newer model
>
> EVB Esr meter
>
> Just got this one
>
> Pros:
> Simple to use
> Well made
> Beautiful display
> Vitor (seller in Portugal) is a great guy! I have NO 
> connection with him
> Based on the proven Dick Smith design
> Has handy chart on front of meter (ballpark numbers)
>
> Cons:
>
> Comes without test leads. (no biggie)
> Awful redesign of the power/calibrate switch! This has 
> been documented by several other users as well. Mine 
> failed in the first 10 minutes of use.
>
> Observations:
> If you look at the EVB site and download the Manual, you 
> will see what the above switch USED to look like. Now, you 
> have to press on the hard plastic front face. This in turn 
> pushes on a plunger, that connects to a small switch on 
> the PC board.
> I replaced this setup with a Radio Shack mini switch that 
> is the exact duplicate of the original design. Works 
> great!!
>
> These observations MAY also hold true for the "Blue ESR 
> Meter". The blue model comes with permanently attached 
> test leads. I actually prefer the EVB setup better, I just 
> wish I had known about the 'no leads included' up front. 
> Again, no biggie.
>
> As you can see, all devices have their +/- aspects. I 
> believe the EVB will become my favorite..............
>
> ron
> N4UE
>
     My only comment is that many caps will test OK for ESR 
and value but have low parallel resistance, AKA, leakage. 
ESR testers usually don't test for this. High leakage is a 
common problem with electrolytic caps because they tend to 
have high leakage even when new, but it _can_ be a problem 
with other types of caps. I've found paper and even plastic 
caps which test OK on an impedance bridge but don't work in 
the circuit. The reason; high leakage.
     I have two methods of testing because I don't have a 
special instrument for making the measurement. I either use 
a small adjustable power supply and a meter capable of 
reading micro-amps, or a General Radio megohmeter. The later 
works fine but has a fixed test voltage of 500V, too high 
for many caps. To use the power supply, I simply hook up the 
cap and meter in series. Thsi particular supply has current 
limiting but a series resistor might be a precaution 
otherwise. I bring the voltage up to the rated voltage while 
watching the amp meter. If the cap is nearly shorted it 
shows up right away and I can shut down the supply. 
Otherwise I bring it up and leave it at the rated voltage 
while watching the meter. For paper, or film caps the 
current should be no more than about 5 uAmps. Modern film 
caps have such low leakage its hard to detect.  I use a 
Tektronix DMM which has enough sensitivity. For 
electrolytics the dielectric layer may take some time to 
form. If its been used recently the dielectric should be OK 
but a cap that's been out of service for some time may take 
half an hour or more to form. Set the voltage at a moderate 
level and watch the current. It should go down with time and 
if it does raise the voltage to the rated voltage in steps. 
A good electrolitic cap should have leakage current of no 
more than about 15 uAmps and it should not rise as the cap 
runs. Again, normal ESR or capacitance bridges may not 
measure electrolytics correctly because they do not bias the 
cap. Without bias the dielectric layer may not be completely 
formed which will affect both value and leakage.



--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com