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Why does Analog Multimeter need AAA Batery
I'll embarrass myself with this one, but so what...
Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery, currently empty. The manual only mentions it and doesn't say why is the battery needed. When I connect the probes to test the power, the needle deflects, correctly indicating voltage/resistance, once again - without the battery present. So what is the battery for then? |
"Newbie" wrote in message
.. . I'll embarrass myself with this one, but so what... Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery, currently empty. The manual only mentions it and doesn't say why is the battery needed. When I connect the probes to test the power, the needle deflects, correctly indicating voltage/resistance, once again - without the battery present. So what is the battery for then? It's needed to measure resistance (ohms). -- Peace, BobJ |
Subject: Why does Analog Multimeter need AAA Batery
Newsgroup: alt.home.repair = Newbie = wrote: I'll embarrass myself with this one, but so what... Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery, currently empty. The manual only mentions it and doesn't say why is the battery needed. When I connect the probes to test the power, the needle deflects, correctly indicating voltage/resistance, once again - without the battery present. So what is the battery for then? It would be needed to measure resistance. How on Earth are you measuring resistance without a voltage source? Tell the truth... Did you REALLY measure a resistor? -- -Graham Remove the snails to email |
The battery is necessary when measuring resistance. If you put the meter
on the resistance scale and touch the probe tips together, the meter should deflect to the zero ohms end if the battery is installed. Newbie wrote: I'll embarrass myself with this one, but so what... Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery, currently empty. The manual only mentions it and doesn't say why is the battery needed. When I connect the probes to test the power, the needle deflects, correctly indicating voltage/resistance, once again - without the battery present. So what is the battery for then? |
Hi Newbie, hope you are having a nice day On 25-Feb-05 At About 13:38:17, Newbie wrote to All Subject: Why does Analog Multimeter need AAA Batery N From: "Newbie" N I'll embarrass myself with this one, but so what... N Just got this little hobbyist's pocket analog multimeter, and it has N a slot for 1 AAA battery, currently empty. The manual only mentions N it and doesn't say why is the battery needed. When I connect the N probes to test the power, the needle deflects, correctly indicating N voltage/resistance, once again -without the battery present. N So what is the battery for then? It is needed for the resistance ( Ohm) readings. -= HvacTech2 =- ... **FLASH** Eveready Bunny arrested, charged with battery. ___ TagDude 0.92á+[DM] ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++ spam protection measure, Please remove the 33 to send e-mail |
"Newbie" wrote in message .. . I'll embarrass myself with this one, but so what... Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery, currently empty. The manual only mentions it and doesn't say why is the battery needed. When I connect the probes to test the power, the needle deflects, correctly indicating voltage/resistance, once again - without the battery present. So what is the battery for then? The only test/s that a simple analog meter (with a needle or moving finger) should require a battery for is continuity/resistance tests. You are correct; an analog meter will measure external sources of electrical voltage and/or current without the battery. However when you desire to measure an inanimate or other wise unpowered circuit or item the source of electricity for that measurement is the small battery inside the meter. By the way don't try to measure any external voltage or current with the meter set to "Ohms" or "Resistance" ranges! For an example; holding a bulb/lamp in your hand you connect the test leads (set to ohms/continuity etc.) to a lamp/bulb in attempt to find out if it's 'blown' or OK? You will not get any reading at all unless that battery is in place! That makes sense of course because current will not flow without a source of voltage. BTW is this a troll? If not suggest that a quick self paced course on basic Ohm's Law will assist advantageous use of the meter and perhaps minimize the chances of "Blowing the sh**" out of it! Which we have all done at one time or another. Also read the little book that should come with the meter. There are some applications where such a small analog meter can do better job than a more sophisticated more sensitive one! |
"Newbie" wrote in message
Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery... what is the battery for then? It's an annoyance. Take the meter out of a drawer, and the battery's dead. You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. Nick |
Thanks Terry, and everyone else for your help. In retrospect it appears sooo
obvious that resistance measurement requires some kind of power source... Thanks again everyone.... "Terry" wrote in message ... | | "Newbie" wrote in message | .. . | I'll embarrass myself with this one, but so what... | | Just got this little hobbyist's pocket analog multimeter, and it has a | slot | for 1 AAA battery, currently empty. The manual only mentions it and | doesn't | say why is the battery needed. When I connect the probes to test the | power, | the needle deflects, correctly indicating voltage/resistance, once again - | without the battery present. So what is the battery for then? | | | The only test/s that a simple analog meter (with a needle or moving finger) | should require a battery for is continuity/resistance tests. | You are correct; an analog meter will measure external sources of electrical | voltage and/or current without the battery. | However when you desire to measure an inanimate or other wise unpowered | circuit or item the source of electricity for that measurement is the small | battery inside the meter. | By the way don't try to measure any external voltage or current with the | meter set to "Ohms" or "Resistance" ranges! | For an example; holding a bulb/lamp in your hand you connect the test leads | (set to ohms/continuity etc.) to a lamp/bulb in attempt to find out if it's | 'blown' or OK? | You will not get any reading at all unless that battery is in place! | That makes sense of course because current will not flow without a source of | voltage. | BTW is this a troll? | If not suggest that a quick self paced course on basic Ohm's Law will assist | advantageous use of the meter and perhaps minimize the chances of "Blowing | the sh**" out of it! Which we have all done at one time or another. | Also read the little book that should come with the meter. There are some | applications where such a small analog meter can do better job than a more | sophisticated more sensitive one! | | |
"It's an annoyance. Take the meter out of a drawer, and the battery's
dead. You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. " Another example of practical advice from pointed head academia. |
nick,
I don't follow this. When the meter is set to measure 120 VAC the battery is not in the circuit and can not be charged, I think. Also can you safely charge non rechargeable batteries? This sounds like very bad advice, especially for a newbie. Dave M. |
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wrote in message ... "Newbie" wrote in message Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery... what is the battery for then? It's an annoyance. Take the meter out of a drawer, and the battery's dead. You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. Nick What's wrong with a spare rechargable battery and a cheap charger. The way I see it you are suggesting a 1.5 volt battery be charged at a rate of 25 ma at 60 volts pulsating DC? Or did you mean 1.5V zener diode? If you were to use a *standard diode* you would be limited to about a half a volt and the battery would never charge. I think you also failed to mention the battery would have to be across only the diode. In any event it would still be a poor charger........Ross |
wrote in message ... "Newbie" wrote in message Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery... what is the battery for then? It's an annoyance. Take the meter out of a drawer, and the battery's dead. You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. Nick Basis of an idea there; as you suggest you'd have to modify the circuit a bit! Probably not worth while because even the simplest kind of primary cell is so cheap (25 to 50 cents?) and available and last so long. Prob. not worth doing it to a simple $6 to $15 'pocket style multimeter'? Rechargeable for a 'digital' display meter might be OK; especially if I tend to leave ours with its LCD display switched on after use!!!!! In a simple analog meter, the battery, which powers only the resistance/continuity scales, is so little used that it will last its shelf life and then some. And since meters tend to be stored in reasonable environment; unless it's in my vehicle glove box and the battery freezes, the battery will normally die of old age rather than use? In a typical analog meter, the battery supplies, and only momentarily, something of the order of one half milliamp (that's one 2000th of one amp for only the few seconds of testing!). So if it does not leak or rust away the battery will have potential for years! I've seen one or two cells that were 20 years old and still had enough potential to fully deflect the meter. After all the batteries in our smoke detectors last a year and they 'are' providing a 'constant' small drain. Keeping a spare pack of the cheapest batteries available a good idea. Also, in effect an analog meter tests its own battery; every time you check FSD for zero ohms; right? BTW on the subject of small cell batteries, including those 9v 'Transistor' style, one of the most useful and productive 'gadgets' is one of those R.Shack battery testers. Sometimes on sale for half price at around $5 to $8. Being congenitally unable to 'not tinker' with anything! Have started to modify our little battery tester, hopefully to enable one hand testing of the continuity of say fuses and/or lamps! Despite that we have several multi-meters; but justify that a combined battery/fuse/lamp tester would result in one less thing (multimeter) to carry around? :-) Suggestions: When you chuck out an old shaver save the zipped and slightly soft padded container, often just right size for a multimeter! By then the cardboard box the meter came in from Taiwan, China or Mexico will have crumbled. And; those soft padded/insulated fabric school lunch 'boxes' are an excellent container for a test instrument, test leads, low wattage AC bulb for checking mains supply, short extension cord, neon tester etc. and a couple of small hand tools. All in one package; so when your favourite Aunt Ida phones and says her lights are blinking, again, and she also needs a new bulb in her flashlight, just grab it and go. Have fun out there! |
On Sat, 26 Feb 2005 16:08:45 GMT, "David Martel"
wrote: nick, I don't follow this. When the meter is set to measure 120 VAC the battery is not in the circuit and can not be charged, I think. Also can you safely charge non rechargeable batteries? This sounds like very bad advice, especially for a newbie. Dave M. You don't want to fool with a rechargeable battery in an analog VOM. For that matter, you don't want one in a digital voltmeter either. Alkaline batteries have a shelf life of several years. As others have already pointed out, the only thing the battery is for is in measuring resistance. This reading depends upon measuring the current flow through resistors in the meter. If there is no battery, there will be no current flow. The meter would work fine for all other measurements because they generate their own source of power to operate the meter. Dick |
"Dick" LeadWinger wrote in message ... On Sat, 26 Feb 2005 16:08:45 GMT, "David Martel" wrote: nick, I don't follow this. When the meter is set to measure 120 VAC the battery is not in the circuit and can not be charged, I think. Also can you safely charge non rechargeable batteries? This sounds like very bad advice, especially for a newbie. Dave M. You don't want to fool with a rechargeable battery in an analog VOM. For that matter, you don't want one in a digital voltmeter either. Alkaline batteries have a shelf life of several years. As others have already pointed out, the only thing the battery is for is in measuring resistance. This reading depends upon measuring the current flow through resistors in the meter. If there is no battery, there will be no current flow. The meter would work fine for all other measurements because they generate their own source of power to operate the meter. Dick Why wouldn't you use a rechargeable battery in a meter? I've had one in my $400 Fluke DMM, sent out for repair and calibration and it came back with the rechargeable still in place. Apparently they didn't have a problem with it nor have I for at least 15+ years. Just curious Dick....take care, Ross |
On Sat, 26 Feb 2005 13:48:48 -0500, "Ross Mac"
wrote: "Dick" LeadWinger wrote in message .. . On Sat, 26 Feb 2005 16:08:45 GMT, "David Martel" wrote: nick, I don't follow this. When the meter is set to measure 120 VAC the battery is not in the circuit and can not be charged, I think. Also can you safely charge non rechargeable batteries? This sounds like very bad advice, especially for a newbie. Dave M. You don't want to fool with a rechargeable battery in an analog VOM. For that matter, you don't want one in a digital voltmeter either. Alkaline batteries have a shelf life of several years. As others have already pointed out, the only thing the battery is for is in measuring resistance. This reading depends upon measuring the current flow through resistors in the meter. If there is no battery, there will be no current flow. The meter would work fine for all other measurements because they generate their own source of power to operate the meter. Dick Why wouldn't you use a rechargeable battery in a meter? I've had one in my $400 Fluke DMM, sent out for repair and calibration and it came back with the rechargeable still in place. Apparently they didn't have a problem with it nor have I for at least 15+ years. Just curious Dick....take care, Ross Maybe it was just a "fluke?" :-) My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead. Dick |
"Dick" LeadWinger wrote in message ... On Sat, 26 Feb 2005 13:48:48 -0500, "Ross Mac" wrote: "Dick" LeadWinger wrote in message . .. On Sat, 26 Feb 2005 16:08:45 GMT, "David Martel" wrote: nick, I don't follow this. When the meter is set to measure 120 VAC the battery is not in the circuit and can not be charged, I think. Also can you safely charge non rechargeable batteries? This sounds like very bad advice, especially for a newbie. Dave M. You don't want to fool with a rechargeable battery in an analog VOM. For that matter, you don't want one in a digital voltmeter either. Alkaline batteries have a shelf life of several years. As others have already pointed out, the only thing the battery is for is in measuring resistance. This reading depends upon measuring the current flow through resistors in the meter. If there is no battery, there will be no current flow. The meter would work fine for all other measurements because they generate their own source of power to operate the meter. Dick Why wouldn't you use a rechargeable battery in a meter? I've had one in my $400 Fluke DMM, sent out for repair and calibration and it came back with the rechargeable still in place. Apparently they didn't have a problem with it nor have I for at least 15+ years. Just curious Dick....take care, Ross Maybe it was just a "fluke?" :-) My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead. Dick I too have Model 87 and a Model 8060A along with two Tek Scopes a couple of True RMS clamps and all of them use rechargeables. Now I must admit that I do keep a spare rechargeable in every case and I used these instruments *alot* ( now retired ). My batteries would require a recharge about once a year and I could even recharge them with my inverter in my truck (fodder for another discussion). I can't say I ever got the life out of a 9V that you did (Duracell) and I always shut the meter off when I wasn't using it and have always been surprised the switch didn't wear out...So now you got the rest of the story....but hey...we all have different use patterns and experiences.......take care Dick, Ross |
"Dick" LeadWinger wrote in message ... On Sat, 26 Feb 2005 13:48:48 -0500, "Ross Mac" wrote: "Dick" LeadWinger wrote in message .. . On Sat, 26 Feb 2005 16:08:45 GMT, "David Martel" wrote: nick, I don't follow this. When the meter is set to measure 120 VAC the battery is not in the circuit and can not be charged, I think. Also can you safely charge non rechargeable batteries? This sounds like very bad advice, especially for a newbie. Dave M. You don't want to fool with a rechargeable battery in an analog VOM. For that matter, you don't want one in a digital voltmeter either. Alkaline batteries have a shelf life of several years. As others have already pointed out, the only thing the battery is for is in measuring resistance. This reading depends upon measuring the current flow through resistors in the meter. If there is no battery, there will be no current flow. The meter would work fine for all other measurements because they generate their own source of power to operate the meter. Dick Why wouldn't you use a rechargeable battery in a meter? I've had one in my $400 Fluke DMM, sent out for repair and calibration and it came back with the rechargeable still in place. Apparently they didn't have a problem with it nor have I for at least 15+ years. Just curious Dick....take care, Ross Maybe it was just a "fluke?" :-) My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead. Dick I have an old led display Fluke (Model 8030A) that uses 4 NiCads. You leave it plugged in when in when possible. http://www.tucker.com/java/jsp/doorw..._invid9533.htm |
On Sat, 26 Feb 2005 17:24:09 -0500, "Ross Mac"
wrote: I too have Model 87 and a Model 8060A along with two Tek Scopes a couple of True RMS clamps and all of them use rechargeables. Now I must admit that I do keep a spare rechargeable in every case and I used these instruments *alot* ( now retired ). My batteries would require a recharge about once a year and I could even recharge them with my inverter in my truck (fodder for another discussion). I can't say I ever got the life out of a 9V that you did (Duracell) and I always shut the meter off when I wasn't using it and have always been surprised the switch didn't wear out...So now you got the rest of the story....but hey...we all have different use patterns and experiences.......take care Dick, Ross I can only surmise that you put the rechargeable in? My Fluke 87 manual clearly does not call for rechargeable. When I got it back from Fluke after calibration, it didn't have one in then either. It had a new battery, as Fluke always puts a new one in. I have only had it recalibrated once as I am a very light and non-critical user. I am still curious as to how you charge the battery in your 87 as there is no provision for doing that. Surely, you don't take the meter apart each time. Dick |
On Sat, 26 Feb 2005 22:26:27 GMT, "Rich" wrote:
"Dick" LeadWinger wrote in message My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead. Dick I have an old led display Fluke (Model 8030A) that uses 4 NiCads. You leave it plugged in when in when possible. http://www.tucker.com/java/jsp/doorw..._invid9533.htm Yes, but you are talking about a bench instrument, not a portable, hand-held like the OP was asking about. Dick |
"Dick" LeadWinger wrote in message ... On Sat, 26 Feb 2005 17:24:09 -0500, "Ross Mac" wrote: I too have Model 87 and a Model 8060A along with two Tek Scopes a couple of True RMS clamps and all of them use rechargeables. Now I must admit that I do keep a spare rechargeable in every case and I used these instruments *alot* ( now retired ). My batteries would require a recharge about once a year and I could even recharge them with my inverter in my truck (fodder for another discussion). I can't say I ever got the life out of a 9V that you did (Duracell) and I always shut the meter off when I wasn't using it and have always been surprised the switch didn't wear out...So now you got the rest of the story....but hey...we all have different use patterns and experiences.......take care Dick, Ross I can only surmise that you put the rechargeable in? My Fluke 87 manual clearly does not call for rechargeable. When I got it back from Fluke after calibration, it didn't have one in then either. It had a new battery, as Fluke always puts a new one in. I have only had it recalibrated once as I am a very light and non-critical user. I am still curious as to how you charge the battery in your 87 as there is no provision for doing that. Surely, you don't take the meter apart each time. Dick Yes, you remove the screws and recharge it....once a year is not that often....I have never had to send the 87 in for repair and cal but the 8060A has been in several times and they have not changed the battery out....,my ..02.....Ross |
On Sat, 26 Feb 2005 13:48:48 -0500, "Ross Mac"
wrote: Why wouldn't you use a rechargeable battery in a meter? I've had one in my $400 Fluke DMM, sent out for repair and calibration and it came back with the rechargeable still in place. Apparently they didn't have a problem with it nor have I for at least 15+ years. Just curious Dick....take care, Ross I just checked on the Fluke website, and the very latest version of the 87, the V series, still uses the same old 9-volt alkaline as used by my 14 year old 87. If yours has a rechargeable, I am certain that someone added it after it was shipped from Fluke. Dick |
"Dick" LeadWinger wrote in message ... On Sat, 26 Feb 2005 22:26:27 GMT, "Rich" wrote: "Dick" LeadWinger wrote in message My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead. Dick I have an old led display Fluke (Model 8030A) that uses 4 NiCads. You leave it plugged in when in when possible. http://www.tucker.com/java/jsp/doorw..._invid9533.htm Yes, but you are talking about a bench instrument, not a portable, hand-held like the OP was asking about. Dick Actually I think the OP probably had a cheap instrument and never gave us a make/model....so hard to say how it would react to rechargeables but if the meter was cheap....it shouldn't make much difference since accuracy would not be an issue with such an instrument.... :) Ross |
"Dick" LeadWinger wrote in message ... On Sat, 26 Feb 2005 13:48:48 -0500, "Ross Mac" wrote: Why wouldn't you use a rechargeable battery in a meter? I've had one in my $400 Fluke DMM, sent out for repair and calibration and it came back with the rechargeable still in place. Apparently they didn't have a problem with it nor have I for at least 15+ years. Just curious Dick....take care, Ross I just checked on the Fluke website, and the very latest version of the 87, the V series, still uses the same old 9-volt alkaline as used by my 14 year old 87. If yours has a rechargeable, I am certain that someone added it after it was shipped from Fluke. Dick Very possible...I will check the site myself....might be one of those situations where we are both correct by situation....not particularly important as long as our fine meters get the job done...and fine they are...take care Dick, Ross |
"Dick" LeadWinger wrote in message ... On Sat, 26 Feb 2005 22:26:27 GMT, "Rich" wrote: "Dick" LeadWinger wrote in message My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead. Dick I have an old led display Fluke (Model 8030A) that uses 4 NiCads. You leave it plugged in when in when possible. http://www.tucker.com/java/jsp/doorw..._invid9533.htm Yes, but you are talking about a bench instrument, not a portable, hand-held like the OP was asking about. Dick It is portable. It came with a carrying case and all. Just that when on the bench you can keep it plugged in to keep the batteries charged. But those LED displays draw a lot of current. |
"Rich" wrote in message ... "Dick" LeadWinger wrote in message ... On Sat, 26 Feb 2005 22:26:27 GMT, "Rich" wrote: "Dick" LeadWinger wrote in message My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead. Dick I have an old led display Fluke (Model 8030A) that uses 4 NiCads. You leave it plugged in when in when possible. http://www.tucker.com/java/jsp/doorw..._invid9533.htm Yes, but you are talking about a bench instrument, not a portable, hand-held like the OP was asking about. Dick It is portable. It came with a carrying case and all. Just that when on the bench you can keep it plugged in to keep the batteries charged. But those LED displays draw a lot of current. I have a number of portable scopes and meters and have always used rechargeables with no problems and that was on meters I used to calibrate to ..001 volts....I'm with you...they work just fine...Ross |
On Sat, 26 Feb 2005 17:46:33 -0500, "Ross Mac"
wrote: "Dick" LeadWinger wrote in message .. . On Sat, 26 Feb 2005 22:26:27 GMT, "Rich" wrote: "Dick" LeadWinger wrote in message My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead. Dick I have an old led display Fluke (Model 8030A) that uses 4 NiCads. You leave it plugged in when in when possible. http://www.tucker.com/java/jsp/doorw..._invid9533.htm Yes, but you are talking about a bench instrument, not a portable, hand-held like the OP was asking about. Dick Actually I think the OP probably had a cheap instrument and never gave us a make/model....so hard to say how it would react to rechargeables but if the meter was cheap....it shouldn't make much difference since accuracy would not be an issue with such an instrument.... :) Ross You're right. It would just be an unnecessary expense. Dick |
On Sat, 26 Feb 2005 17:50:16 -0500, "Ross Mac"
wrote: "Dick" LeadWinger wrote in message .. . On Sat, 26 Feb 2005 13:48:48 -0500, "Ross Mac" wrote: Why wouldn't you use a rechargeable battery in a meter? I've had one in my $400 Fluke DMM, sent out for repair and calibration and it came back with the rechargeable still in place. Apparently they didn't have a problem with it nor have I for at least 15+ years. Just curious Dick....take care, Ross I just checked on the Fluke website, and the very latest version of the 87, the V series, still uses the same old 9-volt alkaline as used by my 14 year old 87. If yours has a rechargeable, I am certain that someone added it after it was shipped from Fluke. Dick Very possible...I will check the site myself....might be one of those situations where we are both correct by situation....not particularly important as long as our fine meters get the job done...and fine they are...take care Dick, Ross Agreed. The Fluke 87 is one of the best investments in test gear that I ever made. Dick |
In alt.home.repair on Sat, 26 Feb 2005 17:46:33 -0500 "Ross Mac"
posted: Actually I think the OP probably had a cheap instrument and never gave us a make/model....so hard to say how it would react to rechargeables but if the meter was cheap....it shouldn't make much difference since accuracy would not be an issue with such an instrument.... :) Ross I believe accuracy should be independent of whether the battery is fully charged or not. They set it up so the measurement is in proportion to a known resistance, so it should read correctly at any battery voltage. (although eventually the battery is too weak to move the needle or power the lcd's.) BTW, everyone mentions alkaline batteries, but one of my digital meters requires a 9-volt carbon zinc battery. An alkaline battery won't fit in the space provided. (Unlike C, D, AA, and AAA batteries, 9 volt batteries are different in size between carbon-zinc and alkaline.) Meirman -- If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary. |
Ross Mac wrote:
You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. What's wrong with a spare rechargable battery and a cheap charger. Well, that way you need two batteries and a charger, and rechargable batteries are more expensive than plain carbon zinc, and the meter may not work well on 1.2 vs 1.5 V, and this arrangement won't monitor house voltage, and it takes more human attention, and it's less fun. The way I see it you are suggesting a 1.5 volt battery be charged at a rate of 25 ma at 60 volts pulsating DC? More like 1 mA, altho that's too much for an Eveready 1212 AAA with a 540 mAh capacity that loses 10% of its energy over a year. That only needs 0.10x540 = 54 mAh over a year, or about 6 microamps on a continuous basis, if the meter is never used for anything else, but the movement might require another 100 microamps. And why waste power in that resistor, vs a charge pump like this, viewed in a fixed font? - C | \ | | | 1.5 V ------------------| |---------------|-------------------- . | | | | | 120V . --- --- . ^ - ------------ | | | | | | / | | | - --- --- --- - _ - Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads. The battery would be a fine smoother and voltage regulator. Harbor Freight stores sell $2.99 digital multimeters. Maybe they need less than 100 uA. My flashlight plugs into the wall. Very convenient, because I know where to find it and don't have to change batteries. My CO and barn heat detectors work that way too, by design, with audible and remote X10 alarms and "non- rechargable" batteries that rarely need changing. I hate changing batteries. I lose my cheap Casio watches with 7 year Li batteries before they go dead. Nick |
wrote:
- C | \ | | | 1.5 V ------------------| |---------------|-------------------- . | | | | | 120V . --- --- . ^ - ------------ | | | | | | / | | | - --- --- --- - _ - Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads. Oops. Q = 340C makes C = 0.0047, or two 0.01s in series in case one shorts. Or a 20 mW LimeLight, with less power. What does it take to power a 648A PIC? Nick |
wrote in message ... Ross Mac wrote: You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. What's wrong with a spare rechargable battery and a cheap charger. Well, that way you need two batteries and a charger, and rechargable batteries are more expensive than plain carbon zinc, and the meter may not work well on 1.2 vs 1.5 V, and this arrangement won't monitor house voltage, and it takes more human attention, and it's less fun. Absolutely incorrect. That is not how a meter works. And anyhow....a spare battery and a charger???....That is not expensive.... Not trying to fire ya up here but those are the facts. The way I see it you are suggesting a 1.5 volt battery be charged at a rate of 25 ma at 60 volts pulsating DC? My math error...E=IR 60PVDC/47Kohms = 1.2ma or so....The incorrect charging rate for a rechargeable. that's too much for an Eveready 1212 AAA with a 540 mAh capacity that loses 10% of its energy over a year. That only needs 0.10x540 Those batteries are normally referred to as "Puny Duty" and typically never make it to 10 recharges... I don't think this is a good recomendation to the NG.... = 54 mAh over a year, or about 6 microamps on a continuous basis, if the meter is never used for anything else, but the movement might require another 100 microamps. And why waste power in that resistor, vs a charge pump like this, viewed in a fixed font? - C | \ | | | 1.5 V ------------------| |---------------|-------------------- . | | | | | 120V . --- --- . ^ - ------------ | | | | | | / | | | - --- --- --- - _ - Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads. The battery would be a fine smoother and voltage regulator. Harbor Freight stores sell $2.99 digital multimeters. Maybe they need less than 100 uA. I cannot make heads nor tales out of your schematic, fixed font or not, but it appears we now have a capacitor in the circuit...what happened to the "diode and resistor" and you still need a regulator since you still have 60 volts across a 1.5 volt battery. And please no, no....not that doorstop 3 buck meter...a good set of leads will cost you more than that thing. That meter is more likely to get you into more trouble than it ever gets you out of. That "THING" would only be good for very crude troubleshooting. This post is beginning to smell of TROLL.....well maybe not....but the bait and switch characteristics are there! My flashlight plugs into the wall. Very convenient, because I know where to find it and don't have to change batteries. My CO and barn heat detectors work that way too, by design, with audible and remote X10 alarms and "non- rechargable" batteries that rarely need changing. I hate changing batteries. I lose my cheap Casio watches with 7 year Li batteries before they go dead. Nick As for connectiong the active and passive circuits in the meter....I want to be there when you try to measure the 240vac coming into the house and you put 120pvdc across that battery with a camera to catch the absolute look of surprise......Ross |
Ross Mac wrote:
You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. What's wrong with a spare rechargable battery and a cheap charger. Well, that way you need two batteries and a charger, and rechargable batteries are more expensive than plain carbon zinc, and the meter may not work well on 1.2 vs 1.5 V, and this arrangement won't monitor house voltage, and it takes more human attention, and it's less fun. Absolutely incorrect. That is not how a meter works. Huh? My math error...E=IR 60PVDC/47Kohms = 1.2ma or so....The incorrect charging rate for a rechargeable. Incorrect, eh? :-) that's too much for an Eveready 1212 AAA with a 540 mAh capacity that loses 10% of its energy over a year. That only needs 0.10x540, ie 6 uA... Those batteries are normally referred to as "Puny Duty" and typically never make it to 10 recharges... Who's talking about recharging? I don't think this is a good recomendation to the NG.... Pity. ...And why waste power in that resistor, vs a charge pump like this, viewed in a fixed font? - C | \ | | | 1.5 V ------------------| |---------------|-------------------- . | | | | | 120V . --- --- . ^ - ------------ | | | | | | / | | | - --- --- --- - _ - Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads. The battery would be a fine smoother and voltage regulator. Harbor Freight stores sell $2.99 digital multimeters. Maybe they need less than 100 uA. I just measured a Craftsman digital VOM... 9 V at 1.54 mA. I cannot make heads nor tales out of your schematic... Pity. That's "tails," BTW. Nick |
wrote in message ... Ross Mac wrote: You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. What's wrong with a spare rechargable battery and a cheap charger. Well, that way you need two batteries and a charger, and rechargable batteries are more expensive than plain carbon zinc, and the meter may not work well on 1.2 vs 1.5 V, and this arrangement won't monitor house voltage, and it takes more human attention, and it's less fun. Absolutely incorrect. That is not how a meter works. Huh? My math error...E=IR 60PVDC/47Kohms = 1.2ma or so....The incorrect charging rate for a rechargeable. Incorrect, eh? :-) that's too much for an Eveready 1212 AAA with a 540 mAh capacity that loses 10% of its energy over a year. That only needs 0.10x540, ie 6 uA... Those batteries are normally referred to as "Puny Duty" and typically never make it to 10 recharges... Who's talking about recharging? I don't think this is a good recomendation to the NG.... Pity. ...And why waste power in that resistor, vs a charge pump like this, viewed in a fixed font? - C | \ | | | 1.5 V ------------------| |---------------|-------------------- . | | | | | 120V . --- --- . ^ - ------------ | | | | | | / | | | - --- --- --- - _ - Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads. The battery would be a fine smoother and voltage regulator. Harbor Freight stores sell $2.99 digital multimeters. Maybe they need less than 100 uA. I just measured a Craftsman digital VOM... 9 V at 1.54 mA. I cannot make heads nor tales out of your schematic... Pity. That's "tails," BTW. Nick Kind of the response I expected....no answers just juvenile quips......PLONK...... |
On Sun, 27 Feb 2005 09:40:27 -0500, "Ross Mac"
wrote: wrote in message ... Ross Mac wrote: You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. The majority of analog multimeters only need the battery to use it as an ohm meter. If only reading voltage, unless it is a transistorized (extremely high impedence) unit the battery is not required. What's wrong with a spare rechargable battery and a cheap charger. Well, that way you need two batteries and a charger, and rechargable batteries are more expensive than plain carbon zinc, and the meter may not work well on 1.2 vs 1.5 V, and this arrangement won't monitor house voltage, and it takes more human attention, and it's less fun. Absolutely incorrect. That is not how a meter works. And anyhow....a spare battery and a charger???....That is not expensive.... Not trying to fire ya up here but those are the facts. The way I see it you are suggesting a 1.5 volt battery be charged at a rate of 25 ma at 60 volts pulsating DC? My math error...E=IR 60PVDC/47Kohms = 1.2ma or so....The incorrect charging rate for a rechargeable. that's too much for an Eveready 1212 AAA with a 540 mAh capacity that loses 10% of its energy over a year. That only needs 0.10x540 Those batteries are normally referred to as "Puny Duty" and typically never make it to 10 recharges... I don't think this is a good recomendation to the NG.... = 54 mAh over a year, or about 6 microamps on a continuous basis, if the meter is never used for anything else, but the movement might require another 100 microamps. And why waste power in that resistor, vs a charge pump like this, viewed in a fixed font? - C | \ | | | 1.5 V ------------------| |---------------|-------------------- . | | | | | 120V . --- --- . ^ - ------------ | | | | | | / | | | - --- --- --- - _ - Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads. The battery would be a fine smoother and voltage regulator. Harbor Freight stores sell $2.99 digital multimeters. Maybe they need less than 100 uA. I cannot make heads nor tales out of your schematic, fixed font or not, but it appears we now have a capacitor in the circuit...what happened to the "diode and resistor" and you still need a regulator since you still have 60 volts across a 1.5 volt battery. And please no, no....not that doorstop 3 buck meter...a good set of leads will cost you more than that thing. That meter is more likely to get you into more trouble than it ever gets you out of. That "THING" would only be good for very crude troubleshooting. This post is beginning to smell of TROLL.....well maybe not....but the bait and switch characteristics are there! My flashlight plugs into the wall. Very convenient, because I know where to find it and don't have to change batteries. My CO and barn heat detectors work that way too, by design, with audible and remote X10 alarms and "non- rechargable" batteries that rarely need changing. I hate changing batteries. I lose my cheap Casio watches with 7 year Li batteries before they go dead. Nick As for connectiong the active and passive circuits in the meter....I want to be there when you try to measure the 240vac coming into the house and you put 120pvdc across that battery with a camera to catch the absolute look of surprise......Ross |
- C
| \ | | | 3 V ------------------| |---------------|-------------------- . | | | | | 120V . --- --- . ^ - ------------ | | | | | | / | | | - --- --- --- - _ - What does it take to power a 648A PIC? That might be an Insteon/X10 interface PIC... The data sheet says it uses about 100 nanoamps at 3 V in sleep mode and 12 microamps at 32 kHz. If it's awake 1% of the time, say 1 second out of 100, when it talks to a central controller, it would need 0.99x0.1+0.01x12 = 0.22 microamps. Q = 340C coulombs and I = 60Q = 0.22x10^-6 amps makes C = 10 pF, theoretically-speaking :-) If we needed more power and worried about overcharging the 2 AAAs, we might use the PIC to measure the voltage and only enable the charge pump as needed. Nick |
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You would also need the battery to test Diodes and transitors.
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Ross Mac wrote:
wrote in message ... SNIP And why waste power in that resistor, vs a charge pump like this, viewed in a fixed font? SNIP Q = 170C coulombs and I = 60Q = 106 x 10^-6 amps makes C = 0.01 microfarads. The battery would be a fine smoother and voltage regulator. Harbor Freight stores sell $2.99 digital multimeters. Maybe they need less than 100 uA. I cannot make heads nor tales out of your schematic, fixed font or not, but it appears we now have a capacitor in the circuit...what happened to the "diode and resistor" and you still need a regulator since you still have 60 volts across a 1.5 volt battery. The "diode and resistor" have been replaced by a "charge pump" (you can google this) for the reason of "why waste power in that resistor." This is not a bait and switch, it is merely an improvement on an earlier proposal. If you remove the battery from Nick's charge pump circuit proposal, you have what's commonly called a "voltage doubler" (you can google this) and the open-circuit output voltage will peak at twice the AC input amplitude, which would be 340V for "normal" 120VAC-RMS input. Limiting the size of the capacitor limits the current output capability. Placing a battery across the output limits the output voltage by shunting the current flowing through the capacitor. Also remember the current=C*dV/dt, and dV/dt peaks at 170volts/sec. So to reiterate, current and voltage have been limited: as long as the battery is there and can accept the current, you do not have 60V, 120V, 340V or whatever, you have 1.5V regulated by the battery and no additional regulator is necessary. I would modify this design by replacing the diode whose anode connects to ground with a zener rated for 2.5 to 5 volts. That way, if the battery should open-circuit, the downstream components won't see the 370V spike, it having been shunted by the zener. Similar "transformerless stepdown" circuits are used to supply regulated 12VDC to motion detectors. I think Nick was off in his original math because he may not have considered that the output diode (the one with the cathode connected to the battery) begins conducting roughly as the AC input wave rises from its -170V minimum, and continues to conduct roughly till the input reaches its 170V maximum (we're ignoring .6V and 1.5V voltage drops across diodes and batteries as insignificant compared to 170V). Therefore the total charge moved per cycle is Q=C*340volts over the full voltage swing of -170 to +170. (I now see and agree with his math ammended in a subsequent post.) Current in amps (coulombs per second) is Q*60 because there are 60 cycles per second. Substituting the suggested value of .0047 uF for C, and current comes out to be 96 microamps. This is not meant to recharge a battery that has been run flat, but rather to compensate for the self-discharge of the battery such that it does not discharge during storage. The question of whether the negative terminal of the battery is connected to an identifiable "common" node in the VOM's internal circuit is left for further consideration. %mod% |
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