On Sat, 19 Nov 2011 13:13:58 -0600, John S <sophi.2@invalid.org> wrote:>On 10/31/2011 9:58 PM, Mike wrote: >> Here's something that may interest some folks here. I just got my new >> Tonghui TH2821A LCR Meter, and I'm starting to become quite impressed. > >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.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.>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?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. Jon
Tonghui TH2821A LCR Meter
Started by ●October 31, 2011
Reply by ●November 20, 20112011-11-20
Reply by ●November 20, 20112011-11-20
On 11/20/2011 6:33 PM, Jon Kirwan wrote:> On Sat, 19 Nov 2011 13:13:58 -0600, John S > <sophi.2@invalid.org> wrote: > >> On 10/31/2011 9:58 PM, Mike wrote: >>> Here's something that may interest some folks here. I just got my new >>> Tonghui TH2821A LCR Meter, and I'm starting to become quite impressed. >> >> 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. > > 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. > >> 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? > > 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. > > JonThanks for your input, Jon. 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%. I don't know how they do it. John S
Reply by ●January 9, 20122012-01-09
John S <sophi.2@invalid.org> wrote:> On 11/20/2011 6:33 PM, Jon Kirwan wrote: >> On Sat, 19 Nov 2011 13:13:58 -0600, John S >> <sophi.2@invalid.org> wrote: >> >>> On 10/31/2011 9:58 PM, Mike wrote: >>>> Here's something that may interest some folks here. I just got my >>>> new Tonghui TH2821A LCR Meter, and I'm starting to become quite >>>> impressed. >>> >>> 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. >> >> 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. >> >>> 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? >> >> 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. >> >> Jon > > Thanks for your input, Jon. > > 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%. > > I don't know how they do it. > > John SJon & John, Sorry for the delay. Have been quite ill. 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. Thanks, Mike
Reply by ●January 9, 20122012-01-09
On 1/9/2012 6:59 PM, Mike wrote:> John S<sophi.2@invalid.org> wrote: > >> On 11/20/2011 6:33 PM, Jon Kirwan wrote: >>> On Sat, 19 Nov 2011 13:13:58 -0600, John S >>> <sophi.2@invalid.org> wrote: >>> >>>> On 10/31/2011 9:58 PM, Mike wrote: >>>>> Here's something that may interest some folks here. I just got my >>>>> new Tonghui TH2821A LCR Meter, and I'm starting to become quite >>>>> impressed. >>>> >>>> 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. >>> >>> 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. >>> >>>> 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? >>> >>> 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. >>> >>> Jon >> >> Thanks for your input, Jon. >> >> 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%. >> >> I don't know how they do it. >> >> John S > > Jon& John, > > Sorry for the delay. Have been quite ill. > > 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. > > Thanks, > > MikeGood 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. Cheers, John S
Reply by ●January 10, 20122012-01-10
== John S <Sophi.2@invalid.org> wrote: > Good to hear from you, Mike. I hope you are recovering rapidly > from your illness. Thanks very much. It will be a continual struggle but I'm starting to get a handle on things. > 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. 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. > 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 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. > 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. 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: http://www.rapidonline.com/pdf/18-4168.pdf 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? > Cheers, > John S Thanks, Mike
Reply by ●January 10, 20122012-01-10
On 1/10/2012 3:37 AM, Mike wrote:> == > John S<Sophi.2@invalid.org> wrote: > > > Good to hear from you, Mike. I hope you are recovering rapidly > > from your illness. > > Thanks very much. It will be a continual struggle but I'm starting > to get a handle on things. > > > 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. > > 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. > > > 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 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. > > > 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. > > 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: > > http://www.rapidonline.com/pdf/18-4168.pdfThanks for the great information!> It looks like it wants 20mA for 14~16h. I don't think 140mA is going > to do it much good:)A bit scary, huh.> But I'm surprised that you only measure 5mA with it turned off. What > voltage are you delivering to the unit?I set the lab supply to 12V. Here is the data I took: Time Meter mA Notes 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
Reply by ●January 10, 20122012-01-10
On 1/10/2012 3:37 AM, Mike wrote:> > It looks like it wants 20mA for 14~16h. I don't think 140mA is going > to do it much good:)BTW, Mike, one of the recommended batteries in the back of the manual is a GP20R8H. Take a look at those specs. John S
Reply by ●January 10, 20122012-01-10
John S <Sophi.2@invalid.org> wrote: >> It looks like it wants 20mA for 14~16h. I don't think 140mA is >> going to do it much good:) > A bit scary, huh. >> But I'm surprised that you only measure 5mA with it turned off. >> What voltage are you delivering to the unit? > I set the lab supply to 12V. > Here is the data I took: > Time Meter mA Notes > 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 Thansk for the excellent data! 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 "http://www.pinsonne-elektronik.de/media/daten/TH2821A%20Operation% 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 http://www.nmr.mgh.harvard.edu/~reese/electrolytics/tec1.pdf 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. Thanks, Mike
Reply by ●January 10, 20122012-01-10
John S <Sophi.2@invalid.org> wrote:> On 1/10/2012 3:37 AM, Mike wrote: > >> >> It looks like it wants 20mA for 14~16h. I don't think 140mA is >> going to do it much good:) > > BTW, Mike, one of the recommended batteries in the back of the manual > is a GP20R8H. Take a look at those specs. > > John SOK, I'm looking at http://www.gpina.com/pdf/GP20R8H_DS.pdf 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. Thanks for the headsup. Mike
Reply by ●January 10, 20122012-01-10
On 1/10/2012 5:04 PM, Mike wrote:> Thansk for the excellent data!My pleasure. I wasn't trying very hard. I'll do better next time.> 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 21:02Well, the snap-off occurred somewhere between 20:19 and 21:02. I'll try to nail it down a bit better next time.> 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 believe you are correct. It was my suspicion as well.> 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.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.> It turns out some of this information is available in the manual at > > "http://www.pinsonne-elektronik.de/media/daten/TH2821A%20Operation% > 20Manual.pdf"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.> 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.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.> 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 > > http://www.nmr.mgh.harvard.edu/~reese/electrolytics/tec1.pdf > > What this says is the ESR curve decreases as the frequency > increases, and doesn't start to flatten until we reach about 10KHz.Yes. I discovered the same thing with the meter and in a CDE paper: www.cde.com/catalogs/AEappGUIDE.pdf Thanks for your link. I've saved the file.> 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.Neither did I. It gives me a good feeling that the meter is telling me the things I want to know.> 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.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.> But next time I go in, I will try to see if there is anything > mounted in that area that might be of interest. > > Thanks, > > MikeI'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. tonghui dot meter dot is_nice at xoxy dot net Cheers, John S
