Yes, the comparison is a bit unfair, especially when the Wizard costs more depending on where you buy it.
The TH2821A is an incredible value for the price. Apparently it is no longer being produced by Tonghui, and the TH2822 is much more expensive. So perhaps they are dropping the price to clear out the remaining inventory.
According to an email I just received on the top853 USB universal programmer, apparently they ship via USPS to the States. So you might get yours a lot sooner, maybe 2 weeks instead of a month.
You have my sympathies (unless you like that climate). I live near Dallas, Texas where the weather can go from 110F in the summer to (rarely) 10F in the winter. We are having a historical drought right now. At the moment it is 68F and sunny. I've entertained the idea of moving to Belize.
That is the major reason I have rejected the idea of moving to Belize. I am in the habit of getting the things I want from Mouser or Digikey or whatever in a couple of days. That wouldn't happen down there.
most of the ESR meters print a table on the front panel that shows the expected ESR for different values of caps. There are some examples on this page:
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The Capacitor Wizard doesn't have a table. Instead, it has some vague instructions by Doug Jones, the designer of the Capacitor Wizard. Here is a section from one of the pdf files:
Well, finding those open caps and good caps was easy. Now lets look at other bad caps that require a little more experience with the Capacitor Wizard and some knowledge about capacitor TYPES and USES.
You probably found caps from 1 to 30 ohms ESR in your bad box. How do you tell the good caps from the bad??
Whether the ESR of a particular capacitor is correct or too high can always be determined by comparing the suspicious capacitor to a known good one of the same value, voltage rating, and type.
Unfortunately one doesn't always have another capacitor to compare against. Experience is the best teacher here, however there are some general guidelines:
The higher the rated working voltage, the higher the normal ESR.
Capacitors used in Power Switching applications need to have really LOW ESR - less than 1/2 ohm Nonpolar Caps are normally less than 1/2 ohm The next logical question about ESR is "How HIGH is TOO HIGH"?
Thats a judgement call that can only be based on experience or comparison to a known good cap (or access to the engineering data from the capacitor or equipment manufacturer - ha ha!). Over 10 ohms is certainly too high for most applications. Over 3 ohms is too high for Horiz/Vert switching applications. Over 1/2 ohm is too high for power switching applications. By comparison you will gain experience and know when to be suspicious. These are my opinions. Here are some actual repair situations:
Example: 47uf @50vdc measures 25 ohms ESR in circuit - BAD CAP The suspect capacitor is a 47uf @50vdc in a switching power supply for a VCR. The Capacitor Wizard has measured 25 ohms ESR in circuit. That is higher than 15 ohms and much to high for any quality cap. A new capacitor measured 5 ohms ESR. The new capacitor fixed the VCR. In my opinion the new capacitor was not of the highest quality (5 ohms is too high) however it did fix the VCR. The use of these low quality inexpensive import capacitors is probably the reason we see so much capacitor failure in con- sumer electronic equipment! A higher quality cap with a lower ESR of the same kind costs more money but will measure less than 1 ohm and be more reliable.
Conclusion: This is a higher voltage capacitor and can be expected to normally measure higher than 1/2 ohm. In my judgment any "switch mode" capacitor that measures more than 3 ohms ESR is suspect no matter what the voltage rating.
However you may obviously get by with the 5 ohms ESR in that particular circuit. For comparison, the bad part was checked "out of circuit" on a well known competitors $2000 Cap analyzer and it determined that the cap was GOOD - even though the ESR measured 25 ohms! That manufacturer made a huge mistake by trying to calculate good and bad ESR from entered and measured data. It can't be done reliably. That is why we don't simply have a good/bad indication on our meter scale. Any cap over 3 ohms is suspect. This is my Experience.
Example: 1000uf @6vdc measures 1.5 ohms in circuit - BAD CAP This is a little brown 1000uf 6vdc cap used in lots of VCR switching power supplies. The Capacitor Wizard measured 1.5 ohms in circuit. Because the capacitors operating voltage is so low (6vdc) and its used in a switching power supply, I would expect a normal ESR reading of less than 1/2 ohm. Comparison to a known good cap confirmed it should measure less than 1/2 ohm. Replacing this cap cured the trouble.
This particular cap goes bad often as I have many in my box of bad caps gathered from local repair compa- nies. If you work on VCRs, I bet you have some too.
Summery: (mrm: sp)
Measuring ESR is a very good indicator of capacitor failure. For switch mode circuits it is the ONLY reliable capacitor test, IN or OUT of circuit!. Open caps and caps with really high ESR (over 10 ohms) are easy to find in circuit and need to be replaced.
Marginal caps that measure between 1 and 10 ohms ESR require some experience with the Capacitor Wizard and/or comparison to a known good cap of the same voltage, value, and type. Caps above an operating voltage of 35vdc have a normally higher ESR (around 1 to 3 ohms) than caps of a lower voltage (less than 1/2 ohm ESR).
I know of no perfect formula or rule that can always tell normal ESR from marginal ESR other than comparison to a known good part. The obvious solution is to obtain the capacitor manufacturers data manuals on the EXACT capacitor measured but that is not normally practical. As a technician myself I always follow this rule: "If in doubt, replace". You will eliminate a lot of recalls and cure many weird and undefinable intermittent problems if you follow this rule.
To find a typical dissipation factor for the Tonghui, I went through several boxes of old electrolytic caps. Regardless of the capacitor value, there seemed to be a clear dividing line between good and bad caps. I settled on D = 0.2 as it seemed to be a reasonable number for most applications, such a bypass and coupling caps.
However, if the application was critical, such as a capacitance multiplier for low level dc supply, I'd look for capacitors with the lowest D value I could find, and put some in parallel.
The interesting thing, and this has me a bit confused, is the dissipation factor does not seem to be affected much by the test frequency.
I would expect the ESR to remain fairly constant with frequency, but the capacitive reactance of course will change. So the impedance of the capacitor will change with frequency, and I would expect the dissipation factor to change also.
I haven't had time to sort this out yet, and I need to get some more experience with this instrument and find out how it is making the measurement. For example, take a known good capacitor and add some series resistance and see what happens to the readings. But here are some wikipedia references to start with:
Winter is not so bad. You get used to digging your car out of snowbanks and scraping ice from the windshield. There were two things I didn't like much about the states. One was the smog in most cities. That started to make me sick. Now I can't even go near Toronto when it is bad.
The other was teenagers with 9 mm and .45 firing them in alleways at night. I got a scanner and started listening to the police trying to catch them. I guess they had scanners also, since I never heard of anyone getting caught.
The nights are very quiet here in Midland, Ontario. The police transmissions are encrypted, so it's a waste of time trying to listen. I used to be able to tell the difference between a 9 mm and a .45, but I haven't heard one for such a long time that I probably forgot what they sound like.
I'd move to Bangkok in an instant. Except right now they are having problems with flooding. But you can get just about any electronic component in minutes, at very cheap prices. And the girls are soooo nice:)
Yeah. I'm on the north side of Dallas and I can smell the fumes when I go outside.
Don't have that around here yet, thankfully.
Usually quiet here, too, except for the annoying loud bass thumping from cars driving by.
I have friends who are pushing me to retire to the Philippines. They say I can have one or more live-in maids, a beachfront house, etc for less than my monthly costs now. It is persuasive.
Foreigners are not allowed to own land in the Philippines, let alone beachfront property, which is probably just as well. Long term leases (eg. 50 years) are possible.
Best regards, Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Mine came in yesterday. Since the wall wart is 220V, it is useless to me so I cut the chord and used a lab power supply to charge it. This got interesting.
With the meter off, the current was only about 5mA. I turned the meter on and the current went to about 140mA. After a period of time which I did not measure, the current dropped back to about 50mA and the battery symbol indicated full charge.
This makes me wonder if fast charge takes place only when the meter is on and it just trickle charges with the meter off. Have you noticed a long charging time with the meter off?
Ordered mine _after_ you and got mine a week ago, partly because I asked them to rush it and they responded by saying they'd heard me and would work quickly. I mentioned that I was US 60Hz 120V, failing to find anything on the topic on the web page, and received email saying that they'd look into it and figure something out.
When it arrived, they had included another wall-wart (about six times heavier and much larger than the one that comes in the package) without a cord but instead an interesting power socket that the "regular" 220V wall wart could plug into. No charge. Just had to ask.
Manual is in chinese, had to download an English version.
I noticed a long charge time when off, but a significantly shorter charge time when on. I hadn't measured the current, though, probably because I didn't need to hack my power supply into bits before using it.
System came up in 'delta' mode, whihc caused me confusion despite seeing the symbol there telling me what probably was going on. I knew what was probably causing the odd readings but until I got the English version manual, I wasn't entirely sure what else to correctly do to fix it. While playing with that before reading the manual, I did uncover how to auto-calibrate it in 'short' and 'open' mode, though.
So far, it's been very nice and I've been impressed with what was included at the price -- including the extra, weighty 110 to 220 wall wart. But I've yet to put it to serious use. I have used it to help quickly figure out the core material types of some randomly collected toroids I have in a drawer, using some windings and calcs. Time will tell, but happy for now.
I'm pretty sure it will charge faster (based on my amperage readings) when power is applied.
I've been subjecting it to tests as well as I can muster. I have a Boonton 71K capacitance meter that I used as a "standard". I have a .01uF, 1% cap Wima cap that I bought because it was the lowest D I could find. The Boonton agrees with the 2821A as best as my eyes will make out considering that the Boonton has an analog meter.
I have a Xicon 18 ohm, 25 watt resistor I measured. In inductance mode, it showed 2.95uH and a Q of .0105 at 10kHz. That calculates to give a series R of about 17.65 ohms. So I then measured the resistance with the
2821 (in the resistance mode) to be 17.73 ohms. Well, then I fired up my HP3456A and measured the resistance at 17.75 ohms.
I am impressed. So far, it has been correct for every test I can give it considering my limited standards situation. Oh, wait! I have some .1% resistors I checked with it. I didn't record the readings, but they were well withing the .1%.
It looks like they sent Jon a 110V to 220V step up transformer. That would explain the weight. After complaining about not being able to run on 110V, they sent me a small, lightweight 110V switching power supply that looked similar to the original 220V unit. I'm surprised they did not send you both the same transformer instead of the 220V version.
I did the initial charging with the instrument turned off. After about 4 hours, it indicated full charge. But I had been playing with it trying to figure out how it worked until I finally decided there was an internal battery that needed charging. So it got at least a partial charge while I was fooling around.
I found the instrument may do strange things until it is fully charged. This makes sense if you consider the uP may not be getting the correct voltage during the initial charging cycle. After it was fully charged, it stopped doing silly things and started giving good results.
Thanks to John for the calibration info. I was also quite impressed with the performance. It is quite outstanding, especially for the price. I think we will get many years of useful work from these units. But I have to caution everyone to make absolutely certain any capacitor is fully discharged before measuring it. I lost a good LCR meter by accidentally losing track of which capacitors were discharged and which were still fully charged. It made a dull thud and stopped working.
So we can't depend on ourself to protect the unit. There has to be dedicated protection circuity.
I'm thinking of making a small adapter with a discharge resistor and a power bridge rectifier across the input terminals. I found the instrument did not respond to having a single diode across the capacitor, so a bridge should have no effect. I'll add a SPDT switch so the dump resistor is normally in the circuit, and have the bridge rectifier across the terminals to the instrument as insurance.
Good to hear from you, Mike. I hope you are recovering rapidly from your illness.
One thing I learned that you may or may not know is, when measuring capacitors, you can switch to the R mode and read the capacitor's ESR directly rather than having to calculate it from D. I was truly pleased to discover that.
When I received my meter, I cut the cord off of the 220V wall wart and used the cord and a lab power supply to charge the meter while watching the current. Very interesting. Unless I did something wrong, I found that the meter will not charge at more than a few mA when in the "off" condition. So, I turned it on and watched the charging current until it took a drop and the bars on the display indicated "full".
The vendor did send me a 120V supply. I have not used it yet, and I think I will charge the meter next time just as I did last time (with a lab supply) and make more measurements until I am comfortable that I have a good feel for the meter's charging characteristics.
Thanks very much. It will be a continual struggle but I'm starting to get a handle on things.
Yes, I discovered that also. I thought it was just a quirk, but it did seem to work reliably on capacitors. BTW, I did find the ESR does decrease rapidly with frequency at low frequencies. It starts to remain constant around 10KHz and above. So the Q does appear to remain the same with different test frequencies below 1KHz. You can see the effect by looking at any electrolytic datasheet.
The charging arrangment seems strange. It looks like they wanted to simplify things by leaving it in trickle charge when it is turned off, then they simply put the charger, the battery, and the instrument in parallel when you turn it on.
I don't even know what kind of battery is inside. I don't think a NiCd will trickle charge at 5mA, and most of the more exotic batteries require special charging circuits to prevent destruction. Maybe I'll take mine apart this weekend and have a look.
First step is to find out what kind of battery is inside. OK, you talked me into doing it now.
Pfaff! First thing I do is drop a screw on the floor. Took five minutes to find it!
The battery is a 200mA/hr 8.4V NiMh. Here's the datasheet:
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It looks like it wants 20mA for 14~16h. I don't think 140mA is going to do it much good:)
But I'm surprised that you only measure 5mA with it turned off. What voltage are you delivering to the unit?
19:21 Off 3.55 Battery indicator at 1 bar
19:32 On 143 Battery indicator at 1 bar
19:40 On 136 Battery alternating between 1 bar and 2 bars
19:44 On 135 Battery at 2 bars
20:27 On 138 Battery alternating between 2 bars and 3 bars
20:19 On 140 Battery at 3 bars
21:02 On 27 Battery at 3 bars
21:06 On 33 Battery at 3 bars
21:10 On 38 Battery at 3 bars
21:15 On 41 Battery at 3 bars
21:20 On 42 Battery at 3 bars
Obviously the battery isn't charging very heavily with the unit turned off. Maybe that is just a trickle charge to keep the battery topped up.
With the unit turned on, it looks like they are really charging the battery at 140mA. It is amazing how the current snaps off at 21:02
I wonder if the 40mA drain with the unit turned on is the normal power drain for the instrument. Actually that's not too bad considering what's inside.
I guess the other thing is NiMh has a pretty severe self-discharge curve. It looks like the unit would have to remain plugged in on standy to keep the battery trickle-charged. Otherwise it would have to go through the complete 140mA charge cycle every time we turn it on. And while it is charging, it may be be usable due to the funny readings.
It turns out some of this information is available in the manual at
"
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20Manual.pdf"
Section 3.3 on page 30 talks about battery recharge. They state it takes 2~3 hrs to charge, and this gives 5~6 hrs of use. They also state twice that it may not operate correctly while charging, which I already found out by trying to fiddle with the unit when it first arrived.
If the battery has 200mAh, and it lasts 5 hrs, that's about 40mA, which is what you measured in the table above. So it is beginning to make some sense.
So, it has a battery, which is nice. But the battery turns out to be a hassle if we are not using the unit constantly, which is a bit of a pain.
Since we cannot predict when we are going to need the unit, it looks like it will have to stay on trickle charge all the time. That's not much of a problem. It doesn't take much power, but probably the biggest hassle will be finding a spare plug.
Further update on the Q of electrolytics. I found some curves on ESR vs Frequency in Fig. 1 - 11 of Impedance, ESR vs. Frequency Characteristics. This is on page 7 of
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What this says is the ESR curve decreases as the frequency increases, and doesn't start to flatten until we reach about 10KHz.
Below that, the ESR increases as we lower the frequency. Since the capacitive reactance is also decreasing, the Dissipation Factor, or Q, will tend to remain constant. And that's what the Tonghui is showing.
I never knew that.
Also, did you notice there is a black strip along the top of the unit? That looks like it might be part of an IR data port. I didn't take the unit completely apart since there was somethng snagging it.
But next time I go in, I will try to see if there is anything mounted in that area that might be of interest.
It shows the same 20 mA for 16 hrs as recommended for this battery. It also shows the fast charge cycle, which requires a charge control circuit. They give the following parameters:
Fast Charge : 100 mA to 200 mA (0.5 to 1C) charge termination control recommended control parameters:
-dV : 0 - 35mV DT/dt ** : 0.8 o C/min (0.5 to 0.9C) : 0.8 - 1 o C/min (1C) TCO ** : 45 - 50 o C
So it looks like they really do intend to do a fast charge. Also, there was no temperature sensor anywhere near the battery when I took it apart, so maybe they are relying on the delta V hump at full charge. I'm not sure how they keep track of things when the user (me) keeps turning the unit on and off, but they do seem to be able to charge the battery since the charge indicator appears to work well.
So it seems they do have things under control. That's good. Gives more confidence that it will continue working as the battery ages.
My pleasure. I wasn't trying very hard. I'll do better next time.
Well, the snap-off occurred somewhere between 20:19 and 21:02. I'll try to nail it down a bit better next time.
I believe you are correct. It was my suspicion as well.
Actually, I took that data on 11/20/2011. I have not charged it since then and it still shows two battery bars remaining. I have used it only occasionally, maybe an hour total, since then. I'm pleased that it is holding up so well.
Yes. I got that manual when you provided the link to me weeks ago. Thanks again. As I mentioned in another post, take a look at the recommended GP20R8H specs as mentioned on page 31. It makes me breathe easier.
I've not had a problem with battery self-discharge, as I mentioned above. I do not leave mine charging all the time, but it might not be a bad thing.
Yes. I discovered the same thing with the meter and in a CDE paper:
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Thanks for your link. I've saved the file.
Neither did I. It gives me a good feeling that the meter is telling me the things I want to know.
Yes, I did. I'm sure it is a data port. I saw something in the manual about reserved function concerning that. For example, see the last bullet on page 5 of the manual.
I'm certain you'll find IR emitter and detector.
It's possible that the contributors on this group don't care about our detailed discussions. I will give you a temporary email address whereby you can reach me and we can then privately exchange more permanent addresses, if you like.
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