ESR-micro Meter

Brooke Clarke 2010

Background
Ranges
DIP Socket 
DC Power
Battery Internal Resistance
Capacitor Test Results Table
Practical Applications
Thoughts on Replacement Caps
Related
Fly Back Tester
Purchase
Links
Version 4.0s
7-segment LCD
ESR
                  Capacitance Meter version 4.0s
Version 4.0 (no longer available)
Dot matrix LCD
ESR-micro
                Meter version 4.0
Version 4.0s Inside
ESR
                  Capacitance Meter Version 4.0s Inside
Inside Version 4.0
ESR-micro
                Meter version 4.0 Inside

Background

This is an Equivalent Series Resistance (ESR) meter is made in Russia by Radio Devices (Google Translation).  It's primary use is to test capacitors for series resistance while they are installed on printed circuit boards.  It uses the ATmega88 microcontroller.  The 2x5 hole pattern to the right of the uC is probably the JTAG programming header. 

The key thing this meter does that other ESR meters do not do is that this one measures BOTH Capacitance and ESR at the same time.  The version 3 ESR-micro had an alternating C then R display, but the version 4 has a two line display.  This tester may give better results for some caps than the prior ESR meters.  Will be running some tests shortly (Jan 2010).  Also there are audio tones that tell you about the resistance of the DUT as well as at power up or down.

More about Capacitor Failure on the Hints & Tips web page.

This ESR meter uses the same method as the Bob Parker unit that is no longer sold by Dick Smith Electronics, but this meter uses a shorter pulse and so does a better job of measuring low value capacitors.  For example it measures a 2.2 uF cap to within +/- 0.1 uF.

Ranges

Cap:    0.2 to 60,000 uF  (Note:  the meter will not measure low ESR Supercaps, but may work on the memory hold up type supercaps)
Res:    0.00 to 99       Ohm (note: can be used as an Ohmmeter for values below 99 Ohms)

DIP Socket

ESR-micro Meter
The cap in the photo ( 22uF 250V) is the same cap that was used in the SR715 photos.
Display is:
ESR = 1.71 Ohms
Cap = 26.3 uF

The DIP socket on the front panel has three uses:
  • The left center sockets are a short (0 Ohm res).  When the meter is powered up with the probes on these sockets a self calibration is done.  This is much easier than trying to hold the probes on a penny and pressing a button (that's best done with three hands).
  • On the left topmost and bottommost sockets are three resistors.  The center resistor is 1.0 Ohms, then 10 Ohms and finally 100 Ohms to confirm a proper calibration.  For the 0, 1 & 10 Ohm resistors you hear the beeper that's proportional to resistance.
  • On the right are two terminals for testing caps with radial leads and the socket pitch varies from 0.1" to 0.7" in 0.1" steps.

DC Power

Two CR2032 3V coin cells are connected in series for a nominal 6 V supply.  When the unit is powered up the battery voltage is displayed for a few seconds (Vbat=5.8v) along with the firmware version.  There is an automatic power off if there's been no activity for 40 seconds.

To change the batteries remove the four (-) screws on the back.  Remove the old batteries using a pointed tool to push back the metal clip.  Install new cells + side up.  When installing the four (-) screws turn them CCW until you feel the screw drop a thread then turn CW.  This avoids cutting new threads in the plastic case.

Battery Internal Resistance

Warning: Reverse Polarity will blow the protection diode and maybe some traces, so this is not recommended for the faint of heart.

If a capacitor is installed in the socket on the left where the zero Ohms calibration is done and then the unit is powered up it will zero out the capacitor if the ESR is below about 2 Ohms.
This means a 10 uF cap is too small, so something like a 470 uF cap will zero the meter.  Note the 10 Volt rating of the cap so this setup is good for batteries up to 9 Volts.

Now if the cap is placed in series with the black test lead with it's negative terminal free and it's positive terminal to the black test lead you're ready to test a battery.

Connect the red lead to the battery positive terminal and connect the negate cap lead to the battery negative terminal (to keep the polarity correct for the cap) and wait a couple of seconds for the reading to stabilize.  Read the batteries internal resistance.

Using a test lead with alligator clips on each end makes this much easier.

Battery ESR Test Results Table

Battery Test AA
              & 9V Cells No. 1 to 10

No.
Batt
Type
Chemistry
OCV

ZTS
# of LED
ESR
Ohms
ESR
Ohms
Comment


Alkaline
Fluke 87V ZTS
ESR-Cap
HP 4328A

1
1.5V
Alkaline 1.098
0
0.36

Dead
2
1.5V Alkaline 1.234
0
0.30

Dead
3
1.5V Alkaline 1.384
3 yel
0.02

so so
4
1.5V Alkaline 1.607
5 grn
0.00

Fresh
5
1.5V Alkaline 0.1xx
0
-----

Dead corroded

6
9V
Alkaline 7.06*
0
6.4

Dead
7
9V Alkaline 1.467
0
72**

Dead
8
9V Alkaline 0.231
0
11.3

Dead
9
9V Alkaline -0.278
0
12.1

Dead
10
9V Alkaline 9.01*
5 grn
2.4

Fresh




Another way to measure battery internal resistance is to use the HP 4328A milli Ohmmeter.  This works for higher voltage batteries.

Capacitor Test Results Table

Moved to it's own Capacitors web page (too many to parts for this page)

Practical Applications

Heathkit GC-1000 Most Accurate Clock

A used Heathkit GC-1000 Most Accurate Clock is not working properly.  The test results when first tested differed from the results a few days later (clock powered up in the mean time).  The results seemed difficult to troubleshoot.  Testing the electrolytic caps showed most of them to be bad.
The following are power supply or decoupling caps where low ESR electrolytics would be good:
C102, C203, C205, C206, C208, C212, C213, C301, C354, C357, C401, C404, C405, C424.
The following are caps where low leakage is important and so either a plastic or low leakage electrolytic would be good:
C348, C353, C355, C359, C412, C414, C421, C422,C425.
Look at the tables on the right side of the page where Red is out of spec and notice that some of the out of spec conditions are for capacitance and some for ESR.

Robertshaw Controller in GE Oven

My electric oven was running too cold last year ago (see: Recipes: 5 Minute Bread) and a couple of weeks ago my stepson baked a pie where the bottom was raw dough.  I had pulled the oven and started shopping for a new one then had sticker shock so decided to see of this one could be repaired.  It turneded out that a couple of caps (C1 & C17 in the analog section of the controller board were bad.  The repair saved $1,000 to $2,000 for a new oven.  See: Hints and Tips: Cold Oven

AM-7176A

This came DOA with a DC short at the 24 Volt Input.
After removing the rear finned high power assembly that included the J3 input connector it was clear using a Fluke 87V DMM that the problem was not in the finned high power assembly but in the main chassis.  Two large blue caps were tested with the ESR-Cap meter with these results:
C1= 0.24 Ohms - 1530 uF [s.b. 01132U050AK - 1300uF 50V] so looks OK
C2= 0.00 Ohms - 1720 uF (Fluke 87V DMM shows falling resistance not short) ESR meter now reads 0.40 Ohms - 1720 uF [s.b. 101172U100AJ2A - 1720 uF  100V] so OK
-----
After taking the chassis apart to gain access to the Input DC Power Supply Filter assembly is was looking like there may be something wrong with the SCR, but none of the DMM measurements made sense, so the ESR meter was used.  The following circuit diagram was drawn:

AM-7176A VHF/UHF RF Amplifier At first I thought that the SCR was the problem (and was thinking that the L1 choke terminal "1" was the input and "2" was the output, but when I came back to the drawing noticed the ESR readings that I've highlighted in red.  The L1 coke measures 0.43 Ohms and it's input terminal "2" shows 1710 uF & 0.48 Ohms to ground.  The L1 choke output terminal "1" shows 0.00 Ohms to ground and 1720 uF.  That means the problem is either with the A1 9V battery charging circuit or with C2.  But C2 is showing 1720 uF which is exactly the label value.  What's going on????
---
After removing the bracket and unscrewing the negative terminal on C2 (see photo on AM-7176A web page Fig 15) both C2 and the rest of the circuit tested OK.  What's going on??
---
When reassembling C2 the answer came.  When the screw holding the terminal lug was tightened the terminal rotated to the right causing the many black wires attached to push into the other terminal.  While there was not a metal to metal short the insulation on maybe a couple of wires was heavily deformed, not enough to make a hard short, but enough to cause a short when a voltage over maybe 10 Volts was applied.  By using the shank of a pocket Phillips screwdriver to reform the black wires they were moved away from the positive terminal and the problem is solved.

A minor concern is the 1k resistor that is between the 2N685 SCR gate and cathode (ground) which measures 37 Ohms in either polarity using the DMM and ESR-Cap meter.  It looks like the only way the SCR can turn on is if the input voltage goes over 200 so this may be part of the EMP (wiki) protection scheme.  This is similar to the crowbar protection circuit used to short the output of a power supply when it's voltage exceeds some threshold, but in this case the gate voltage will never be as high (or higher) than the anode and so will never turn on by the gate.  That only leaves the breakdown voltage as a turn on mechanism.

There has been some discussion of where to place surge protectors (Wiki) and the answer seems to be as close to the input as possible.  In this case it's just after the circuit breaker.




Thoughts on Replacement Caps

It turns out that more than half of the electrolytic and Tantalum caps in the GC-1000 are bad (either low capactiance or very high ESR or both).  Rather than use new plain electrolytics I'd like to use better quality caps.
1.    Where there is an available replacement (radial, adaquate DC working voltage) using Aluminum Organic Polymer caps adds a whole lot of reliability.
        It turns out that these are only available in a very limited number of physical and electrical values and are 10 to 100 times more expensive. 
        A better choice may be either the Low ESR electrolytic or the Low Leakage electrolytic, a plastic or ceramic cap depending on the application.
2    Using low loss electrolytics for things like the NE567 PLL or op amps would be good or plastic.
3.    Low ESR electrolytics would be better for power supply decoupling.

Related

Test Equipment
HP 4260A Universal Bridge
HP 4274 & HP 4275 LCR Meters
HP 4332 HP 4332 LCR Meter
HP 4395A Combined Network, Spectrum & Impedance Analyzer
Impedance - in general
Megger - Holtzer-Cabot Meg Ohmmeter ZM-14A/PSM-2
TF2700 Marconi TF-2700 Universal Bridge
Zo Transmission Line Impedance (is not constant with frequency)
ZM4 - DC Bridge
ZM-11 - Capacitance-Inductance-Resistance Bridge
EVB ESR Tester
SR715 LCR Meter

Fly Back Tester

This is a tester that's made by the same company that makes the combined ESR - Cap meter (Google translation).

It's based on another of Bob Parker's designs, the LOPT / FBT tester, K7205.pdf)

The Fly Back Tester works by looking for the ringing of an inductor.  It's use is not limited to fly back transformers.  For example in the second photo below it's connected to a loop antenna and the right hand LED is green (Good).
If interested let me know.
FB Tester
Fly Back
                        Inductor Tester Inside AT Tiny
on the back side of the PCB is the CR2032 coin cell and on the front side (shown at left) is the AT Tiny microcontroller.
FB Tester shows green
                      on Loop Antenna
Showing good (right hand LED is green)
when connected to Loop antenna.
(high Q at 60 kHz)




Purchase

Click the button for U.S. or International sales on the Products for Sale web page.
Price includes U.S.P.S. mail First Class delivery and Calif. sales tax if you're here.

Links

Back to Brooke's Home, Optics, Wet Batteries, Products for Sale, Military Information web pages.
[an error occurred while processing this directive] Page created 2 Feb 2010.