+++++++++++++++++++ Date: Fri, 25 Oct 2002 14:45:43 -0400 From: "Mark J. Dulcey" To: glen houghton Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] Recommendations for Multimeters glen houghton wrote: > Just getting back into electronics and thinking about building an K1 and if the goes well I might try a K2 or have someone build it for me. > > What is the best multimeter for building radio kits etc? I see a larger variety than I had in the past. Anything special I should look for? PC interface is this usefull or not? There are so many choices out there that naming a single "best" meter would be impossible. But I'll offer some advice anyway. First, just about any DMM (digital multimeter), even the ones that sell for under $10 at hamfests, has enough capability and accuracy for all the measurements you will need in an Elecraft kit, with one possible exception that I'll get to. This is NOT true of a VOM (volt-ohm meter); those cause enough circuit loading to make some measurements inaccurate. (A VOM is an analog meter with no active circuits.) An old VTVM (vacuum tube volt meter) would work fine, but they're collectible these days, so you would probably pay more for one than for a decent DMM. What you get with a more expensive DMM is a bigger display, a more rugged case, better probes, more accuracy (not necessary for the Elecraft kits, but it might come in handy for other uses), possibly more capabilities (capacitance, inductance, transistor gain, temperature, and frequency counting are all things that I have seen), a brand name, and a warranty that actually means something. So, why might you want to pay more? First, a bigger display is nice. It's easier to read. If you have trouble reading any of the portable meters, even the large ones, you might want to consider a bench DMM; they plug into the wall and have glowing digits of one sort or another. Most of them are horribly expensive new, so you'd want to look for a good used meter at a hamfest. A more rugged case is good. The meter will last longer. Better probes will also last longer; you can replace cheap probes with better ones, but that's an extra expense that you can avoid if you buy a meter that comes with good ones. Capacitor measurement is one extra feature that I'm a big fan of; it saved my butt a couple of times when I was building my K2. Some modern capacitors have very difficult to read markings, like the ones with tan bodies and red digits in the K2; putting them on the meter can help you figure out which parts are which. A feature that I haven't used personally, but that other people here have praised, is an "analog" bar graph in addition to the digital display. It's handy for peaking and nulling adjustments, and often updates more quickly than the digital display on the same meter. One feature that I personally DON'T like is autoranging. I prefer to know what I'm measuring before I measure it, rather than having the meter make decisions for me. Some DMMs, particularly portables, are auto-ranging only; other are switchable auto/manual, and some are manual-only. If your budget permits, you might supplement your DMM with an analog meter. (Even a VOM is fine, so long as you are aware of its limitations; mostly, you don't want to use it for exact voltage measurements when you're doing the voltage checks or troubleshooting in your Elecraft rig.) They are still handier for some measurements than any digital meter. They're expensive new these days, so watch the hamfests. So what do I use? At home, I use a Beckman Industrial (now Wavetek-Meterman) DM27XT. It's a full-featured DMM that includes inductance and capacitance scales. It's held up to 15 years of use here, including the building of my K2 and all the modules. The Harvard classes based on the Art of Electronics use the very same meter in the classroom labs, and they have held up to years of student abuse, aside from the fact that the students blow a lot of fuses. (I've never needed to change the fuse in my own meter.) For quickly checking things out at hamfests, I use a $7 hamfest special; it's smaller than the Beckman, and I'm not out much if I lose it. Finally, I also have an old Radio Shack VOM that I built from a kit about 25 years ago; it only occasionally sees use these days. +++++++++++++++ From: "Stuart Rohre" To: "glen houghton" , Subject: Re: [Elecraft] Recommendations for Multimeters Date: Fri, 25 Oct 2002 13:52:53 -0500 Good buys at Harbor Freight on digital multimeter including a transistor check capability. Also, Home Depot even has inexpensive DMM under 25 dollars. Check the various distributors, Mouser, Digi Key, also AES, Ham Radio Outlets, etc. 73, Stuart K5KVH ++++++++++++++++++ To: houghtonglen at hotmail.com, elecraft at mailman.qth.net Date: Fri, 25 Oct 2002 12:57:32 -0700 Subject: Re: [Elecraft] Recommendations for Multimeters From: k6se at juno.com Glen, KG4SEV wrote: "What is the best multimeter for building radio kits etc? I see a larger variety than I had in the past. Anything special I should look for? PC interface is this usefull or not?" ========== The main thing I can think of that makes a DMM especially useful if you have to troubleshoot an Elecraft radio (or nay other radio) is to make sure that its input resistance on the DC Volts ranges is 10 megohms. Then you can be sure that a simple RF probe you build for the meter (such as the one described in the K2 manual - and for which the parts are supplied with the kit) will yield reasonably accurate readings when used with the DMM. Many inexpensive DMMs do not meet this requirement and the resultant readings are perhaps only 10% of the actual signal voltage. If I recall correctly, some of the alignment steps for the K2 require using the RF probe with your DMM to measure small signal levels. A PC interface is nice, but not essential. 73, de Earl, K6SE +++++++++++++++++ From: "Stuart Rohre" To: , , Subject: Re: [Elecraft] Recommendations for Multimeters Date: Fri, 25 Oct 2002 16:56:33 -0500 Re pc interface for a DMM. Most DMMs are used to avoid having to get out the big guns of a computer controlled measurement system. They are portable and quick, to troubleshoot and solve your problem without recourse to other instrumentation except perhaps a signal source. Thus, 99 44/100 per cent of DMM work can be done without hooking to a PC. PC interface is mainly for when you are wanting to catalog production line repetitive measurements of the same voltage or current from many different devices of the same type or a few types. The more complete the meter the better. It should have mainly wide coverage of AC and DC voltages, current and resistance. Other nice to have features are diode test, transistor gain tests, and measurements like capacitor value. Nice to have but added easily as outboard test boards is inductance measurement. Decibel readout and ability to reference 0 dB are nice to haves for much audio work. A bar graph or auxiliary analog meter are needed for peaking and nulling ease of measure. 73, Stuart K5KVH ++++++++++++++ From: "Stuart Rohre" To: , "glen houghton" Cc: Subject: Re: [Elecraft] Recommendations for Multimeters Date: Fri, 25 Oct 2002 17:06:27 -0500 This is a great buy, free DMM with nice features including some useful in other troubleshooting than that needed to build the kit. It has analog bar graph, temperature and limited frequency measurement capability in addition to the desirable features I listed for a generic DMM in my other posting. Look on the web tronics site and search on "DMM" to get the full specs of this offer. 73, Stuart K5KVH ++++++++++++++ Message: 7 From: "Francis Belliveau" To: Subject: Re: [Elecraft] Recommendations for Multimeters Date: Sat, 26 Oct 2002 17:46:04 -0400 On: Friday, October 25, 2002 2:45 PM "Mark J. Dulcey" wrote: > ... > One feature that I personally DON'T like is autoranging. I prefer to know what I'm measuring before I measure it, rather than having the meter make decisions for me. Some DMMs, particularly portables, are auto-ranging only; other are switchable auto/manual, and some are manual-only. > ... I agree with Mark. Auto ranging may have it uses when you are measuring components out of circuit or stable voltages. A number of tests Elecraft kits require is the resistance between two points in a circuit without power applied. Using a manual range setting you will get different readings on different settings due to how the voltage is applied and how the circuit reacts to it. This will often confuse autoranging meters. Therefore the recommendation here is to make sure it will allow manual range selection. 73, Fran, KA4FRH K2 s/n 314 +++++++++++++++++ From: "Sandy, W5TVW" To: "Francis Belliveau" , Subject: Re: [Elecraft] Recommendations for Multimeters Date: Sun, 27 Oct 2002 00:01:44 -0500 You might checkout "Harbor Freight" company on the web. They have a very excellent little DVM that is the old range switch type. It works VERY well, and sells for $9.95. If you catch a special at one of their sales, it goes for $4.95! Don't let the cheap price fool you, it is a good meter! 73, Sandy W5TVW +++++++++++++++++ To: ebjr at i-55.com Cc: flb at attbi.com, elecraft at mailman.qth.net Date: Sun, 27 Oct 2002 08:56:46 -0800 Subject: Re: [Elecraft] Recommendations for Multimeters From: k6se at juno.com Sandy, W5TVW wrote: "You might checkout "Harbor Freight" company on the web. They have a very excellent little DVM that is the old range switch type. It works VERY well, and sells for $9.95. If you catch a special at one of their sales, it goes for $4.95! Don't let the cheap price fool you, it is a good meter!" ========== Yes, it's a good little meter (I have two of them) but unfortunately it won't work with an RF probe because of its low input resistance. 73, de Earl, K6SE ++++++++++++++++++ From: "Don Brown" To: "Elecraft" Subject: Re: [Elecraft] Recommendations for Multimeters Date: Tue, 29 Oct 2002 09:50:30 -0600 Hi A friend of mine have been having a friendly argument for years about buy= ing cheap or buying quality. I think it started with 1/4 drill motors abo= ut 20 years ago but it applies to DMM's also. You can buy a $10 - $20 DMM= and it will work fine in most applications and you can buy one for $100+= and it will do the same. The difference is how well it is made an how we= ll it will take abuse. A quality meter will take a drop off of the bench= or ladder and keep on working. Forget and measure 120 AC on ohms and it = wont bother it. They come with a really nice set of probes that would cos= t you more than the cheap meter if you bought them separately. You can ge= t it fixed if it breaks or you can get the parts to do it yourself if you= want to. It can be recalibrated if needed and if you look at the specs t= he better meter is most likely more accurate. There is also the quality f= eel to a well made piece of gear and something you can depend on. We woul= dn't be building Elecraft kits if we didn't think that. So that is my arg= ument for the $100+ DMM My friend's argument is I can buy the cheap meter when it breaks go get a= nother one. I can do that 4 or 5 times and still come out ahead. They are= throw away items. I guess he has a point but there is the hassle of gett= ing another one just when you need it. =20 I am not saying the cheap meter wont last a long time if you take care of= it, just the odds of it getting broken or burned out are higher than the= better meter. I have several Fluke meters, one is very old (20+ years) t= hat still meet all specs. This is typical for the quality meters. My preference is a good quality DMM like Fluke Tektronix or Beckman and I= don't mind paying a little more fore something that I will have a long t= ime. You may feel like my friend and that's OK we all are entitled to our= opinion. :-) BTY I have a MaKita cordless drill motor He has several $15 Black & Decke= r's he bought in garage sales. To each his own. Don Brown KD5NDB ++++++++++++++++++ Date: Tue, 29 Oct 2002 11:24:48 -0500 To: elecraft at mailman.qth.net From: "L. D. Ingram" Subject: [Elecraft] Elecraft] Recommendations for Multimeters HI, One thing I have not seen in all the comments about multimeters is a mention of the response time of the digital display which is related to the sampling or count rate. Most of the less expensive meters have longer sampling times/lower count rates which means you have to wait longer for the reading after connecting the probes. I have a friend that has an older Radio Shack DMM which I find very frustrating to use because of the wait compared to my Fluke. Obviously this is something you can live with if you have to but it does pay to check the response time, however they state it, when buying a DMM. Unfortunately this information is not always given, but a shorter response time is one of the things you usually pay for in the more expensive meters. Larry Ingram AG4NN K2 #2529 ++++++++++++++++++++ From: "Stuart Rohre" To: , "L. D. Ingram" Subject: Re: [Elecraft] Elecraft] Recommendations for Multimeters Date: Tue, 29 Oct 2002 12:03:31 -0600 Response time is not a problem for the cheaper Harbor Freight DMM, nor the ones from Home Depot. This was a problem in the early days of Radio Shack DMMs with theirs, I believe it is not a concern with faster A/Ds and micro controllers of today. They use the same micro in any 3 1/2 DMM, in a given manufacturers line of models. 73, Stuart K5KVH (economics of scale) +++++++++++++++++++ From: "Don Brown" To: "L. D. Ingram" , "Elecraft" Subject: Re: [Elecraft] Elecraft] Recommendations for Multimeters Date: Tue, 29 Oct 2002 12:40:40 -0600 Hi Many of the Fluke meters have a response time of about 4 readings per sec= ond for the digital display but on the analog bar graph the time is 40 re= adings per second making it good for peaking and dipping measurements Don Brown KD5NDB +++++++++++++++++++ Subject: Re: [Elecraft] Elecraft DMM vs VOM To: "Don Brown" , elecraft at mailman.qth.net From: Martin.Evans at simoncarves.com Date: Thu, 27 Mar 2003 15:32:40 +0000 Thanks Don, Yeah I guess 22.5V is not good idea for semiconductors. OK on forward biasing semiconductors, so you have to be careful what/where you are measuring. I haven't got to the testing parts yet in the manual but when I do I will use the DVM. Thanks for the explanation. BTW it's great to have such a wealth of advise on tap. Back to toroid winding! 73's Martin (M0KWV) "Don Brown" on 27/03/2003 15:06:10 To: , cc: Subject: Re: [Elecraft] Elecraft DMM vs VOM Hi Many of the older VOM's such as the Simpson and Triplet types had a high voltage battery in the ohms circuit. If I remember right this wad a 22 1/2 volt battery. They also had 1 D cell battery used for the lower ranges. The possible high voltage or high current applied to the circuit under test could damage semiconductors. If your meter only has a 3 volt battery it will probably not hurt the circuits. However a DVM uses a different method of measuring Ohms than a VOM so the readings may be different from the manual. In fact there has been some confusion in the past with variations in DVM readings on ohms. Resistance measurements are ballpark only. The problem is the way the meter reads resistance and how much voltage is applied to the circuit. Some meters on some ranges will forward bias semiconductors and some will not giving different readings. I put more faith in the voltage tests in the manual. They should be very close to the manual. Don Brown KD5NDB ++++++++++++++++++ From: "Don Brown" To: "Bob - AG5Q" , , Subject: Re: [Elecraft] Elecraft DMM vs VOM Date: Thu, 27 Mar 2003 12:16:50 -0600 Hi If Bob doesn't mind. The resistor isolates the RF circuit from the capacitance of the DVM and the inductance of the leads. Many times just probing a RF circuit will upset it or in some cases causes it to stop working. The high input resistance of the DVM prevents the resistor at the probe tip from affecting the reading much. BTY this is the same reason a X10 probe is used on a scope, more to reduce the loading capacitance rather than the resistance. The resistance is increased by 10 but the capacitance is reduced by 10 Don Brown KD5NDB Subject: Re: [Elecraft] Elecraft DMM vs VOM To: "Bob - AG5Q" , elecraft at mailman.qth.net From: Martin.Evans at simoncarves.com Date: Thu, 27 Mar 2003 16:32:14 +0000 Thanks for the tips Bob. But why do you need a resistor to isolate the probe if the DVM has a very high impedance anyway? "Bob - AG5Q" on 27/03/2003 15:58:56 To: , cc: Subject: Re: [Elecraft] Elecraft DMM vs VOM Hi Martin, The VOM is good for continuity checking since you can see the meter swing out of the corner of your eye. A lot of DMMs have a buzzer for continuity checking which is very handy. Well worth a little extra cost. The best feature of the DMM is accuracy. A lot of problems in circuits can be found by making accurate DC measurements and looking for abnormal readings. When troubleshooting, the first thing I do is take some readings and write them on the schematic and then look to see if they are consistent. Ninety percent of the time the trouble will show up as an abnormal DC reading, even in RF circuits. It's a good idea to use a resistor (10K-50K) to isolate the probe from RF circuits. Wrap one end of the resistor around the meter probe and use the other end of the resistor as the probe. 73/ Bob - AG5Q +++++++++++++++++++