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Need help with new DMMeter

8/19/1998 4:04 PM
markg	Need help with new DMMeter Well I've been using my old VOM but it isn't very accurate. Also it doesn't work in the DCma range any more. Does it need to be very expensive or can I get away with between $50-$90? My needs are for working with tube amps, setting bios, checking resistors down to 1ohm, caps, and the regular ac/dc functions. I also would like trans/diode test with it. Thanks mark greenwald

8/19/1998 4:04 PM

markg

Need help with new DMMeter

Well I've been using my old VOM but it isn't very accurate. Also it doesn't work in the DCma range any more.
Does it need to be very expensive or can I get away with between $50-$90?
My needs are for working with tube amps, setting bios, checking resistors down to 1ohm, caps, and the regular ac/dc functions. I also would like trans/diode test with it.
Thanks
mark greenwald

8/19/1998 5:09 PM
loudernhel	Mark, $50 to $90 should buy you plenty of meter. Most people I see buy a bunch more features thaan they need. I'm a professional ET in the Coast Guard and the meter I use at work is nowhere near as elaboate as what some people buy to use in installing the occasional pickup. Here's what I think you need: 1) Autoranging is really nice to have )VDC & VAC 2) Millivolts Dc (for bias across a 1 ohm load) 3) Milliamps DC (for ot shunt bias) 4) resistance 5) Diode check. The ability to measure capacitance is debateable. Caps are cheap if you think one is bad put another in. I also see little sockets to test a transistor in on some DMMS. That's not needed if you have a diode check. Even serious circuit wonks never use a temperature probe. Invest in a good lead kit. ITT Pomona makes one that comes in a little roll up vinyl pouch. It has a needle point probe to slip over aa regular lead. Also the ends of the leads are modular so you can pull them off and put different accesories on like alligator clips, clip/clips, etc. David Becker loudernhel@aol.com

8/19/1998 5:09 PM

loudernhel

Mark,

$50 to $90 should buy you plenty of meter. Most people I see buy a bunch more features thaan they need. I'm a professional ET in the Coast Guard and the meter I use at work is nowhere near as elaboate as what some people buy to use in installing the occasional pickup.

Here's what I think you need: 1) Autoranging is really nice to have )VDC & VAC 2) Millivolts Dc (for bias across a 1 ohm load) 3) Milliamps DC (for ot shunt bias) 4) resistance 5) Diode check.

The ability to measure capacitance is debateable. Caps are cheap if you think one is bad put another in. I also see little sockets to test a transistor in on some DMMS. That's not needed if you have a diode check. Even serious circuit wonks never use a temperature probe.

Invest in a good lead kit. ITT Pomona makes one that comes in a little roll up vinyl pouch. It has a needle point probe to slip over aa regular lead. Also the ends of the leads are modular so you can pull them off and put different accesories on like alligator clips, clip/clips, etc.

David Becker
loudernhel@aol.com

8/19/1998 6:28 PM
Graywater	2- cents. I like the capacitance measurement to match caps for a few applications like phase inverters. Also, when comparing tone circuit designs I like to know what the component values are. GW

8/19/1998 7:52 PM
markg	David My reason for the capacitor function is to read unlabeled caps when time or a schematic isn't available. As for the Ohms function the autorange sounds good but would it be anymore accurate with the smaller values? Or would the range still be (200, 1k, 10k etc.)? I would like a smaller range for the accuracy. The lead kit sounds like a good investment and helpful accessories. Thanks mark greenwald mgriz@m2000.net

8/19/1998 7:52 PM

markg

David
My reason for the capacitor function is to read unlabeled caps when time or a schematic isn't available.
As for the Ohms function the autorange sounds good but would it be anymore accurate with the smaller values? Or would the range still be (200, 1k, 10k etc.)? I would like a smaller range for the accuracy.
The lead kit sounds like a good investment and helpful accessories.
Thanks
mark greenwald
mgriz@m2000.net

8/20/1998 12:12 PM
loudernhel	Fair enough about the cap function. Another guy said he likes to use it to match caps. I've been led to believe that the cap functions on a dmm aren't as accurate as a dedicated cap checker. I don't know if this difference is non-triviaal or not. It doesn't matter if you're going for just a ballpark value. For matching caps two that have the same indicated value should have the same actual value. I'm not sure I understand your question about the autorange feature and the resistance measurement. I'm not aware of an autoranging DMM being any less accurate here. David Becker loudernhel@aol.com

8/20/1998 12:12 PM

loudernhel

Fair enough about the cap function. Another guy said he likes to use it to match caps. I've been led to believe that the cap functions on a dmm aren't as accurate as a dedicated cap checker. I don't know if this difference is non-triviaal or not. It doesn't matter if you're going for just a ballpark value. For matching caps two that have the same indicated value should have the same actual value.

I'm not sure I understand your question about the autorange feature and the resistance measurement. I'm not aware of an autoranging DMM being any less accurate here.

David Becker
loudernhel@aol.com

8/20/1998 3:05 PM
markg	Sorry I should have gave a more accurate example. What I was describing was the multimeter ranges. On an analog which I use the ranges for Ohms goes R x 1, R x 10, R x 100....etc. When using the R x 1 scale measuring eg. 1ohm resistors it is hard to know how close it is to true "1ohm" because of the variables in the meter and the scale is not very fine. My question was, does the DMM autoranging give you a more accurate reading or are the ranges basically the same as analog just automatic and not any truer? It might give a reading of 1.050 for a said 1ohm resistor. Where as looking at a needle pointing close to the "1" on the scale its a close guess. My thought is that as in most things you get what you pay for. But how good of a meter is necessary to get the accuracy necessary for Amp and small electronic applications? Thanks markg

8/20/1998 3:05 PM

markg

Sorry I should have gave a more accurate example. What I was describing was the multimeter ranges. On an analog which I use the ranges for Ohms goes R x 1, R x 10, R x 100....etc. When using the R x 1 scale measuring eg. 1ohm resistors it is hard to know how close it is to true "1ohm" because of the variables in the meter and the scale is not very fine.
My question was, does the DMM autoranging give you a more accurate reading or are the ranges basically the same as analog just automatic and not any truer? It might give a reading of 1.050 for a said 1ohm resistor. Where as looking at a needle pointing close to the "1" on the scale its a close guess. My thought is that as in most things you get what you pay for. But how good of a meter is necessary to get the accuracy necessary for Amp and small electronic applications?
Thanks
markg

8/20/1998 3:28 AM
paul perry	well I'm glad my meter (about $40) has got transistor Hfe, because you can just stick a transistor in different ways until you see which way works.. easiest way to get the leads right. Also make sure there is an audible continuity buzzer, so you dont have to look at the display while you are inside the speaker box! And, you casn use the cap range to find which end of a guitar lead is broke, by measuring the centre-to-sheild cap.

8/20/1998 3:28 AM

paul perry

well I'm glad my meter (about $40) has got transistor Hfe, because you can just stick a transistor in different ways until you see which way works.. easiest way to get the leads right. Also make sure there is an audible continuity buzzer, so you dont have to look at the display while you are inside the speaker box! And, you casn use the cap range to find which end of a guitar lead is broke, by measuring the centre-to-sheild cap.

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