All About Circuits Forum Rent or borrow ESR Meter in Pittsburgh area?
 Register Blogs FAQ Members List Today's Posts Search Today's Posts Mark Forums Read

 General Electronics Chat Discussion forum for general chat about anything electronics related, including asking questions about material in the All About Circuits E-book, Worksheets, and Videos.

#1
11-11-2010, 02:21 PM
 spinnaker Senior Member Join Date: Oct 2009 Location: Pittsburgh, PA U.S.A. Posts: 3,640
Rent or borrow ESR Meter in Pittsburgh area?

Does anyone know where I can rent (at a reasonable cost) or borrow an ESR meter in the Pittsburgh area?

A suggestion in this thread said I might have a bunch of bad filter caps in my non working Tek scope. It would probably be just as easy to just replace them since they probably need to be replaced anyway but it would be nice to know if the caps are my problem. Where can I get one of these things aside from shelling out the \$\$\$ to buy one.

I know I can build one with another scope, a function generator or a 555 timer (and I guess even a PIC which I have on hand). But I do not have a another scope.
#2
11-11-2010, 02:57 PM
 bertus Super Moderator Join Date: Apr 2008 Location: Amsterdam,Holland (GMT + 1) Posts: 11,586

Hello,

Why not make one yourself?
Here is a schematic with a PCB:
http://kakopa.com/ESR_meter/index.html

Bertus
__________________
You don't have to know everything, if you know where to find it.
When you do ask questions, you may look stupid.
When you do NOT ask questions, you will STAY stupid.

It would be nice to have the Timezone ( GMT +/- x ) in the location field in the profile.
(User CP -> Edit Your Details)
#3
11-11-2010, 03:07 PM
 spinnaker Senior Member Join Date: Oct 2009 Location: Pittsburgh, PA U.S.A. Posts: 3,640

Quote:
 Originally Posted by bertus Hello, Why not make one yourself? Here is a schematic with a PCB: http://kakopa.com/ESR_meter/index.html Bertus
The problem with that is I do not have most of those parts on hand. And I would need to have confidence that I had it working right.
#4
11-11-2010, 03:20 PM
 bertus Super Moderator Join Date: Apr 2008 Location: Amsterdam,Holland (GMT + 1) Posts: 11,586

Hello,

If you would buy one, what would be the budget?
Here is a kit for \$79 or completerly assembled for \$109:
http://www.anatekcorp.com/blueesr.htm

Bertus
__________________
You don't have to know everything, if you know where to find it.
When you do ask questions, you may look stupid.
When you do NOT ask questions, you will STAY stupid.

It would be nice to have the Timezone ( GMT +/- x ) in the location field in the profile.
(User CP -> Edit Your Details)
#5
11-11-2010, 04:01 PM
 spinnaker Senior Member Join Date: Oct 2009 Location: Pittsburgh, PA U.S.A. Posts: 3,640

Quote:
 Originally Posted by bertus Hello, If you would buy one, what would be the budget? Here is a kit for \$79 or completerly assembled for \$109: http://www.anatekcorp.com/blueesr.htm Bertus

Yeah I have seen them for around \$80 built.

http://cgi.ebay.com/In-Circuit-Capac...item3f04b2d609
#6
11-11-2010, 04:39 PM
 someonesdad Senior Member Join Date: Jul 2009 Location: Northwest USA Posts: 1,584

For us hobbyists, measuring ESR usually involves observing the change of a voltage Vo in the attached circuit when the capacitor under test (modeled by the pure capacitance and the ESR (equivalent series resistance) in the dashed box) is inserted in the voltage divider circuit. Two test leads are often run from the capacitor connection points to allow in-circuit testing. The method is:

Set V to the voltage and frequency you want to test at. Measure Vo with no capacitor attached; call the measured value V1. Then attach the capacitor to be tested and measure Vo again; call this value V2. Then an estimate of the ESR of the capacitor is made from the ratio V2/V1.

The lower the ratio V2/V1, the lower the ESR is -- and the capacitor's impedance is better at shorting out the voltage across R2. An ideal capacitor would short out the voltage completely, making the voltage V2 zero.

You calibrate your ESR checker with some resistors -- say, 0.1, 1, and 10 ohms. You substitute these for the capacitor and measure their voltage ratios just like you would for a capacitor. You can plot R versus the voltage ratio to let you estimate a capacitor's ESR from the graph.

So, if you wanted to make a practical checker, what should you use for V? A function generator is the usual choice or you can make your own oscillator. Another choice could be a 6.3 VAC filament transformer. This will test at line frequency; the usual test for filter caps is at twice the line frequency because they're filtering a full-wave rectified signal. But this is an order-of-magnitude test, so line frequency should be fine. Commercial ESR testers often test at 1, 10, and 100 kHz besides line and twice-line frequencies.

You'll want to choose the resistors R1 and R2 to ensure you put appropriate voltages across the capacitor. If you're doing in-circuit testing, the voltages should be kept low enough to avoid making any semiconductor junctions conduct. Possible starting values are R1 = 1 kΩ and R2 = 5 Ω. Use what you have on hand. You can use a DMM to measure the voltages if you don't have a scope as long as you keep the frequency of V in the DMM's bandwidth. This is a comparative and screening measurement, so accuracy of measurement tools isn't all that important.

I haven't tried this with a filament transformer, but it should work OK for big filter caps. I have used the method with a function generator and a scope and it works well for frequencies in the 10 kHz - 100 kHz range.

Added in edit: Make sure the capacitor is discharged before you measure it. Also, a shorted capacitor will appear to be a good capacitor with this test, so you might want to check a vanishing-ESR capacitor with a DC resistance measurement.
Attached Images
 ESR.jpg (66.4 KB, 73 views)

Last edited by someonesdad; 11-11-2010 at 05:00 PM.
#7
11-11-2010, 05:06 PM
 spinnaker Senior Member Join Date: Oct 2009 Location: Pittsburgh, PA U.S.A. Posts: 3,640

Quote:
 Originally Posted by someonesdad For us hobbyists, measuring ESR usually involves observing the change of a voltage Vo in the attached circuit when the capacitor under test (modeled by the pure capacitance and the ESR (equivalent series resistance) in the dashed box) is inserted in the voltage divider circuit. Two test leads are often run from the capacitor connection points to allow in-circuit testing. The method is: Set V to the voltage and frequency you want to test at. Measure Vo with no capacitor attached; call the measured value V1. Then attach the capacitor to be tested and measure Vo again; call this value V2. Then an estimate of the ESR of the capacitor is made from the ratio V2/V1. The lower the ratio V2/V1, the lower the ESR is -- and the capacitor's impedance is better at shorting out the voltage across R2. An ideal capacitor would short out the voltage completely, making the voltage V2 zero. You calibrate your ESR checker with some resistors -- say, 0.1, 1, and 10 ohms. You substitute these for the capacitor and measure their voltage ratios just like you would for a capacitor. You can plot R versus the voltage ratio to let you estimate a capacitor's ESR from the graph. So, if you wanted to make a practical checker, what should you use for V? A function generator is the usual choice or you can make your own oscillator. Another choice could be a 6.3 VAC filament transformer. This will test at line frequency; the usual test for filter caps is at twice the line frequency because they're filtering a full-wave rectified signal. But this is an order-of-magnitude test, so line frequency should be fine. Commercial ESR testers often test at 1, 10, and 100 kHz besides line and twice-line frequencies. You'll want to choose the resistors R1 and R2 to ensure you put appropriate voltages across the capacitor. If you're doing in-circuit testing, the voltages should be kept low enough to avoid making any semiconductor junctions conduct. Possible starting values are R1 = 1 kΩ and R2 = 5 Ω. Use what you have on hand. You can use a DMM to measure the voltages if you don't have a scope as long as you keep the frequency of V in the DMM's bandwidth. This is a comparative and screening measurement, so accuracy of measurement tools isn't all that important. I haven't tried this with a filament transformer, but it should work OK for big filter caps. I have used the method with a function generator and a scope and it works well for frequencies in the 10 kHz - 100 kHz range. Added in edit: Make sure the capacitor is discharged before you measure it. Also, a shorted capacitor will appear to be a good capacitor with this test, so you might want to check a vanishing-ESR capacitor with a DC resistance measurement.
Any reason it has to be 6.3 VAC?

The shack has a 12V CT .

They have a 12.6 but does not say if it is CT.

I also have a PIC on hand. Could I just use it? What frequency should I use for a pulse?

What is the safest way to discharge those big caps?
#8
11-11-2010, 05:51 PM
 thatoneguy Senior Member Join Date: Feb 2009 Location: Midwest USA Posts: 6,356 Blog Entries: 4

Quote:
 Originally Posted by spinnaker Yeah I have seen them for around \$80 built. http://cgi.ebay.com/In-Circuit-Capac...item3f04b2d609

The BlueESR is awesome. I would suggest getting the kit, it is really hard to do "wrong". I use mine nearly daily, and have nothing bad to say about it!
__________________
$\small{\fra{1}{\fra{1}{R_1}+\fra{1}{R_2}+{\dots}+{ \fra{1}{R_N}}}$ Nifty? -Click Here to see how to make your formulas Look GOOD!
Also-Impedance Graph paper.
#9
11-11-2010, 08:08 PM
 spinnaker Senior Member Join Date: Oct 2009 Location: Pittsburgh, PA U.S.A. Posts: 3,640

Quote:
 Originally Posted by thatoneguy The BlueESR is awesome. I would suggest getting the kit, it is really hard to do "wrong". I use mine nearly daily, and have nothing bad to say about it!
Other than getting the caps on this scope tested. I can't imagine what I would use it for. I will mainly be working with digital, mcus and such. It is hard to justify spending \$80 on something I will probably not use.
#10
11-11-2010, 08:23 PM
 thatoneguy Senior Member Join Date: Feb 2009 Location: Midwest USA Posts: 6,356 Blog Entries: 4

Quote:
 Originally Posted by spinnaker Other than getting the caps on this scope tested. I can't imagine what I would use it for. I will mainly be working with digital, mcus and such. It is hard to justify spending \$80 on something I will probably not use.
I use it a lot of the time as a battery tester/matcher. It is very accurate and can tell you the state of charge on the battery.

It also lets you know the ESR of a cap (obviously), and can alert you to some problems in an etched PCB track from the ability to measure very low resistance.

With digital stuff, you'll be working with power supplies, and being able to go through the whole supply in a few seconds to rule out a lot of cap related issues speeds things up.

If you don't use it that often, no need to get one, but I was amazed at the uses I found for an AC Ohmmeter.
__________________
$\small{\fra{1}{\fra{1}{R_1}+\fra{1}{R_2}+{\dots}+{ \fra{1}{R_N}}}$ Nifty? -Click Here to see how to make your formulas Look GOOD!
Also-Impedance Graph paper.

 Tags area, borrow, esr, meter, pittsburgh, rent

 Related Site Pages Section Title Textbook What is a meter? : Dc Metering Circuits

 Similar Threads Thread Thread Starter Forum Replies Last Post The Electrician General Electronics Chat 8 02-21-2010 02:51 AM alphacat General Electronics Chat 2 01-31-2010 04:51 PM timarlop The Projects Forum 6 01-21-2010 07:16 AM DaveH General Electronics Chat 23 10-04-2009 02:46 PM dj54557 Homework Help 0 10-20-2008 03:52 PM

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Electronics Forums     General Electronics Chat     The Projects Forum     Homework Help     Electronics Resources Software, Microcomputing, and Communications Forums     Programmer's Corner     Embedded Systems and Microcontrollers     Computing and Networks     Radio and Communications Circuits and Projects     The Completed Projects Collection Abstract Forums     Math     Physics     General Science All About Circuits Commmunity Forums     Off-Topic     The Flea Market     Feedback and Suggestions

All times are GMT. The time now is 09:37 AM.