MOTM

O.k., it's time to admit it. I'm bluffing through this modular-building
thing!

That's right--Every one of my modules has worked perfectly after I've built
it, and that's because I'm extremely careful and don't do anything unless
I'm very sure of what I'm doing.

But here's the problem. I can't seem to figure out my DVM. I've read the
manual, I bought another DVM book at Radio Shack, I've read a couple of
introductory electronics books, but for some reason I can't get my head
around a couple of things.

For example: I was calibrating my MOTM-110 yesterday, and even without my
probes touching anything (quit snickering in the back), I was reading
something like 29 volts. Once I was "hooked in," I put the jumper between
+15 and the jack (you know what I mean?), watched the meter, and turned the
trimpot. Nothing. No change.

I feel like whenever I turn on the voltmeter for anything other than testing
batteries, I'm in for a rollercoaster ride of frustration. I quit using my
B&K, which was supposedly a good instrument, because I thought it must be
broken--I could never get predictable results. Now I have the Radio Shack
DVM that Paul designed, and I'm just confused.

Thanks for the modules, Paul! I had the most amazing groove going yesterday
with the ring mod/vca, sub-octave multiplexer, 420, an EG, an old
Hewlett-Packard function generator, a 606 and a 303 (for the CV out). Wow. I
have never, ever, ever heard a synthesizer do that. My jaw just dragged
around the floor for an hour.

Anyway, if anyone has a pearl of wisdom about DVMs, please drop them my way.
Luckily I don't actually need it as the modules work just fine and I was
able to do the alternate (non-DVM) calibration of the 110.

Take care,

David Bivins
Creative Strategist & Transistor Rhythmer
Brandscape
New York City
212.285.2600.x103

Generally, when reading voltages you want the black lead attached to
"ground". The coax shield braid is a good ground on the MOTM stuff. the red
or Positive lead is then used to measure the various voltages you want. Hope
this helps.
Jim

>From: "David Bivins" <david@...>
>Reply-To: motm@onelist.com
>To: "Motm@Onelist. Com" <motm@onelist.com>
>Subject: [motm] Hey, look at me, I'm a dumb-ass.
>Date: Mon, 2 Aug 1999 10:13:11 -0400
>
>From: "David Bivins" <david@...>
>
>O.k., it's time to admit it. I'm bluffing through this modular-building
>thing!
>
>That's right--Every one of my modules has worked perfectly after I've built
>it, and that's because I'm extremely careful and don't do anything unless
>I'm very sure of what I'm doing.
>
>But here's the problem. I can't seem to figure out my DVM. I've read the
>manual, I bought another DVM book at Radio Shack, I've read a couple of
>introductory electronics books, but for some reason I can't get my head
>around a couple of things.
>
>For example: I was calibrating my MOTM-110 yesterday, and even without my
>probes touching anything (quit snickering in the back), I was reading
>something like 29 volts. Once I was "hooked in," I put the jumper between
>+15 and the jack (you know what I mean?), watched the meter, and turned the
>trimpot. Nothing. No change.
>
>I feel like whenever I turn on the voltmeter for anything other than
>testing
>batteries, I'm in for a rollercoaster ride of frustration. I quit using my
>B&K, which was supposedly a good instrument, because I thought it must be
>broken--I could never get predictable results. Now I have the Radio Shack
>DVM that Paul designed, and I'm just confused.
>
>Thanks for the modules, Paul! I had the most amazing groove going yesterday
>with the ring mod/vca, sub-octave multiplexer, 420, an EG, an old
>Hewlett-Packard function generator, a 606 and a 303 (for the CV out). Wow.
>I
>have never, ever, ever heard a synthesizer do that. My jaw just dragged
>around the floor for an hour.
>
>Anyway, if anyone has a pearl of wisdom about DVMs, please drop them my
>way.
>Luckily I don't actually need it as the modules work just fine and I was
>able to do the alternate (non-DVM) calibration of the 110.
>
>Take care,
>
>David Bivins
>Creative Strategist & Transistor Rhythmer
>Brandscape
>New York City
>212.285.2600.x103
>
>
>--------------------------- ONElist Sponsor ----------------------------
>
>You can WIN $100 to Amazon.com by starting a new list at ONElist.
>Drawing is held each week through August 20. For details, go to
>http://www.onelist.com/info/onereachsplash3.html
>
>------------------------------------------------------------------------

Also, you have to set the meter to read either Volts DC or Volts AC,
whatever you are trying to look at. Trying to read volts with the meter set
to read resistance won't increase your sanity!

Moe

> -----Original Message-----
> From: james holloway [mailto:jimh54@...]
> Sent: Monday, August 02, 1999 10:53 AM
> To: motm@onelist.com
> Subject: Re: [motm] Hey, look at me, I'm a dumb-ass.
>
>
> From: "james holloway" <jimh54@...>
>
> Generally, when reading voltages you want the black lead attached to
> "ground". The coax shield braid is a good ground on the MOTM
> stuff. the red
> or Positive lead is then used to measure the various voltages you
> want. Hope
> this helps.
> Jim
>
>
> >From: "David Bivins" <david@...>
> >Reply-To: motm@onelist.com
> >To: "Motm@Onelist. Com" <motm@onelist.com>
> >Subject: [motm] Hey, look at me, I'm a dumb-ass.
> >Date: Mon, 2 Aug 1999 10:13:11 -0400
> >
> >From: "David Bivins" <david@...>
> >
> >O.k., it's time to admit it. I'm bluffing through this modular-building
> >thing!
> >
> >That's right--Every one of my modules has worked perfectly after
> I've built
> >it, and that's because I'm extremely careful and don't do anything unless
> >I'm very sure of what I'm doing.
> >
> >But here's the problem. I can't seem to figure out my DVM. I've read the
> >manual, I bought another DVM book at Radio Shack, I've read a couple of
> >introductory electronics books, but for some reason I can't get my head
> >around a couple of things.
> >
> >For example: I was calibrating my MOTM-110 yesterday, and even without my
> >probes touching anything (quit snickering in the back), I was reading
> >something like 29 volts. Once I was "hooked in," I put the jumper between
> >+15 and the jack (you know what I mean?), watched the meter, and
> turned the
> >trimpot. Nothing. No change.
> >
> >I feel like whenever I turn on the voltmeter for anything other than
> >testing
> >batteries, I'm in for a rollercoaster ride of frustration. I
> quit using my
> >B&K, which was supposedly a good instrument, because I thought it must be
> >broken--I could never get predictable results. Now I have the Radio Shack
> >DVM that Paul designed, and I'm just confused.
> >
> >Thanks for the modules, Paul! I had the most amazing groove
> going yesterday
> >with the ring mod/vca, sub-octave multiplexer, 420, an EG, an old
> >Hewlett-Packard function generator, a 606 and a 303 (for the CV
> out). Wow.
> >I
> >have never, ever, ever heard a synthesizer do that. My jaw just dragged
> >around the floor for an hour.
> >
> >Anyway, if anyone has a pearl of wisdom about DVMs, please drop them my
> >way.
> >Luckily I don't actually need it as the modules work just fine and I was
> >able to do the alternate (non-DVM) calibration of the 110.
> >
> >Take care,
> >
> >David Bivins
> >Creative Strategist & Transistor Rhythmer
> >Brandscape
> >New York City
> >212.285.2600.x103
> >
> >
> >--------------------------- ONElist Sponsor ----------------------------
> >
> >You can WIN $100 to Amazon.com by starting a new list at ONElist.
> >Drawing is held each week through August 20. For details, go to
> >http://www.onelist.com/info/onereachsplash3.html
> >
> >------------------------------------------------------------------------
>
>
> --------------------------- ONElist Sponsor ----------------------------
>
> Create a list for FRIENDS & FAMILY...
> ...and YOU can WIN $100 to Amazon.com. For details, go to
> http://www.onelist.com/info/onereachsplash3.html
>
> ------------------------------------------------------------------------
>

Thanks to Dave and James so far.

I *really* appreciate the help! I *do* know how to set it up and have used
it effectively for many tasks, including past calibrations of a power supply
and another MOTM module. My problem probably can't be solved by the listers
(though I hope it can!) and I think it's that I don't have enough real-world
experience with it, and a mentor (or tutorial) to guide me through it.

I read the books, etc. and I find that if I were working on a refrigerator,
e.g., I'd be fine ;)

I just wonder for example, why my DVM reads 27 volts when it's set to Volts
DC and the probes are hanging, unconnected to anything? These are my
demons--the odd little things that aren't documented in books or instruction
manuals...

I somehow feel that if I understood that, I would understand why that
trimpot didn't do anything to the reading.

Paul--to your recollection, there's no "HEY IDIOT YOU HAVE TO PRESS THIS
BUTTON FIRST" button on the DVM you designed, is there? Power on, dial it to
DC Volts should be good enough, right?

David.

> -----Original Message-----
> From: Dave Bradley [mailto:daveb@...]
> Sent: Monday, August 02, 1999 12:04 PM
> To: motm@onelist.com
> Subject: RE: [motm] Hey, look at me, I'm a dumb-ass.
>
>
> From: "Dave Bradley" <daveb@...>
>
> Also, you have to set the meter to read either Volts DC or Volts AC,
> whatever you are trying to look at. Trying to read volts with the
> meter set
> to read resistance won't increase your sanity!
>
> Moe
>
> > -----Original Message-----
> > From: james holloway [mailto:jimh54@...]
> > Sent: Monday, August 02, 1999 10:53 AM
> > To: motm@onelist.com
> > Subject: Re: [motm] Hey, look at me, I'm a dumb-ass.
> >
> >
> > From: "james holloway" <jimh54@...>
> >
> > Generally, when reading voltages you want the black lead attached to
> > "ground". The coax shield braid is a good ground on the MOTM
> > stuff. the red
> > or Positive lead is then used to measure the various voltages you
> > want. Hope
> > this helps.
> > Jim
> >
> >
> > >From: "David Bivins" <david@...>
> > >Reply-To: motm@onelist.com
> > >To: "Motm@Onelist. Com" <motm@onelist.com>
> > >Subject: [motm] Hey, look at me, I'm a dumb-ass.
> > >Date: Mon, 2 Aug 1999 10:13:11 -0400
> > >
> > >From: "David Bivins" <david@...>
> > >
> > >O.k., it's time to admit it. I'm bluffing through this modular-building
> > >thing!
> > >
> > >That's right--Every one of my modules has worked perfectly after
> > I've built
> > >it, and that's because I'm extremely careful and don't do
> anything unless
> > >I'm very sure of what I'm doing.
> > >
> > >But here's the problem. I can't seem to figure out my DVM.
> I've read the
> > >manual, I bought another DVM book at Radio Shack, I've read a couple of
> > >introductory electronics books, but for some reason I can't get my head
> > >around a couple of things.
> > >
> > >For example: I was calibrating my MOTM-110 yesterday, and even
> without my
> > >probes touching anything (quit snickering in the back), I was reading
> > >something like 29 volts. Once I was "hooked in," I put the
> jumper between
> > >+15 and the jack (you know what I mean?), watched the meter, and
> > turned the
> > >trimpot. Nothing. No change.
> > >
> > >I feel like whenever I turn on the voltmeter for anything other than
> > >testing
> > >batteries, I'm in for a rollercoaster ride of frustration. I
> > quit using my
> > >B&K, which was supposedly a good instrument, because I thought
> it must be
> > >broken--I could never get predictable results. Now I have the
> Radio Shack
> > >DVM that Paul designed, and I'm just confused.
> > >
> > >Thanks for the modules, Paul! I had the most amazing groove
> > going yesterday
> > >with the ring mod/vca, sub-octave multiplexer, 420, an EG, an old
> > >Hewlett-Packard function generator, a 606 and a 303 (for the CV
> > out). Wow.
> > >I
> > >have never, ever, ever heard a synthesizer do that. My jaw just dragged
> > >around the floor for an hour.
> > >
> > >Anyway, if anyone has a pearl of wisdom about DVMs, please drop them my
> > >way.
> > >Luckily I don't actually need it as the modules work just fine
> and I was
> > >able to do the alternate (non-DVM) calibration of the 110.
> > >
> > >Take care,
> > >
> > >David Bivins
> > >Creative Strategist & Transistor Rhythmer
> > >Brandscape
> > >New York City
> > >212.285.2600.x103
> > >
> > >
> > >--------------------------- ONElist Sponsor
> ----------------------------
> > >
> > >You can WIN $100 to Amazon.com by starting a new list at ONElist.
> > >Drawing is held each week through August 20. For details, go to
> > >http://www.onelist.com/info/onereachsplash3.html
> > >
> >
> >------------------------------------------------------------------------
> >
> >
> > --------------------------- ONElist Sponsor ----------------------------
> >
> > Create a list for FRIENDS & FAMILY...
> > ...and YOU can WIN $100 to Amazon.com. For details, go to
> > http://www.onelist.com/info/onereachsplash3.html
> >
> > ------------------------------------------------------------------------
> >
>
>
> --------------------------- ONElist Sponsor ----------------------------
>
> How do you enter ONElist�s WEEKLY DRAWING for $100?
> By joining the FRIENDS & FAMILY program. For details, go to
> http://www.onelist.com/info/onereachsplash3.html
>
> ------------------------------------------------------------------------
>

I'll go out on a limb here and suggest that reading 27V on an unconnected
very high impedance DVM is not unusual. That might be what the potential
is across the test leads, or at least what the DVM is measuring. If it
reads 27V when you short the leads together, then you have a problem!

John Speth
Object Engineering, Inc
mailto:johns@...

On Monday, August 02, 1999 9:45 AM, David Bivins
[SMTP:david@...] wrote:

> I just wonder for example, why my DVM reads 27 volts when it's set to

Volts

> DC and the probes are hanging, unconnected to anything? These are my
> demons--the odd little things that aren't documented in books or

instruction

> manuals...

Is it possible it is an autoranging meter and you are really reading mv
instead of volts? If that's the case then it is nothing to worry about.
Jim

>From: John Speth <johns@...>
>Reply-To: motm@onelist.com
>To: "'motm@onelist.com'" <motm@onelist.com>
>Subject: RE: [motm] Hey, look at me, I'm a dumb-ass.
>Date: Mon, 2 Aug 1999 10:11:51 -0700
>
>From: John Speth <johns@...>
>
>I'll go out on a limb here and suggest that reading 27V on an unconnected
>very high impedance DVM is not unusual. That might be what the potential
>is across the test leads, or at least what the DVM is measuring. If it
>reads 27V when you short the leads together, then you have a problem!
>
>John Speth
>Object Engineering, Inc
>mailto:johns@...
>
>On Monday, August 02, 1999 9:45 AM, David Bivins
>[SMTP:david@...] wrote:
> > I just wonder for example, why my DVM reads 27 volts when it's set to
>Volts
> > DC and the probes are hanging, unconnected to anything? These are my
> > demons--the odd little things that aren't documented in books or
>instruction
> > manuals...
>
>
>
>--------------------------- ONElist Sponsor ----------------------------
>
>You can WIN $100 to Amazon.com by starting a new list at ONElist.
>Drawing is held each week through August 20. For details, go to
>http://www.onelist.com/info/onereachsplash3.html
>
>------------------------------------------------------------------------
>

Yes, that's possible :)

It's difficult to go into when I'm at work, ostensible strategizing the
development of e-commerce sites--I already keep several synths at a time at
work, but if I brought in my DVM they might think I've given up on what I'm
being paid to do altogether!

Thanks for your help!

David.

> -----Original Message-----
> From: james holloway [mailto:jimh54@...]
> Sent: Monday, August 02, 1999 3:31 PM
> To: motm@onelist.com
> Subject: RE: [motm] Hey, look at me, I'm a dumb-ass.
>
>
> From: "james holloway" <jimh54@...>
>
> Is it possible it is an autoranging meter and you are really reading mv
> instead of volts? If that's the case then it is nothing to worry about.
> Jim
>
>
> >From: John Speth <johns@...>
> >Reply-To: motm@onelist.com
> >To: "'motm@onelist.com'" <motm@onelist.com>
> >Subject: RE: [motm] Hey, look at me, I'm a dumb-ass.
> >Date: Mon, 2 Aug 1999 10:11:51 -0700
> >
> >From: John Speth <johns@...>
> >
> >I'll go out on a limb here and suggest that reading 27V on an unconnected
> >very high impedance DVM is not unusual. That might be what the potential
> >is across the test leads, or at least what the DVM is measuring. If it
> >reads 27V when you short the leads together, then you have a problem!
> >
> >John Speth
> >Object Engineering, Inc
> >mailto:johns@...
> >
> >On Monday, August 02, 1999 9:45 AM, David Bivins
> >[SMTP:david@...] wrote:
> > > I just wonder for example, why my DVM reads 27 volts when it's set to
> >Volts
> > > DC and the probes are hanging, unconnected to anything? These are my
> > > demons--the odd little things that aren't documented in books or
> >instruction
> > > manuals...
> >
> >
> >
> >--------------------------- ONElist Sponsor ----------------------------
> >
> >You can WIN $100 to Amazon.com by starting a new list at ONElist.
> >Drawing is held each week through August 20. For details, go to
> >http://www.onelist.com/info/onereachsplash3.html
> >
> >------------------------------------------------------------------------
> >
>
>
> --------------------------- ONElist Sponsor ----------------------------
>
> ONElist members are using Shared Files in great ways!
> http://www.onelist.com
> Are you? If not, see our homepage for details.
>
> ------------------------------------------------------------------------
>

I'll agree with John here.

I always short the test leads to make sure it zeroes out.

I think this was a necesssity with the older analog meters for reading ohms.
If I remember, there was actually a thumbwheel to adjust for zero.

Is it possible that the DVM's also require shorting to set to zero?

Mark T


-----Original Message-----
From: John Speth <johns@...>
To: 'motm@onelist.com' <motm@onelist.com>
Date: Monday, August 02, 1999 1:26 PM
Subject: RE: [motm] Hey, look at me, I'm a dumb-ass.

>From: John Speth <johns@...>
>
>I'll go out on a limb here and suggest that reading 27V on an unconnected
>very high impedance DVM is not unusual. That might be what the potential
>is across the test leads, or at least what the DVM is measuring. If it
>reads 27V when you short the leads together, then you have a problem!
>
>John Speth
>Object Engineering, Inc
>mailto:johns@...
>
>On Monday, August 02, 1999 9:45 AM, David Bivins
>[SMTP:david@...] wrote:
>> I just wonder for example, why my DVM reads 27 volts when it's set to
>Volts
>> DC and the probes are hanging, unconnected to anything? These are my
>> demons--the odd little things that aren't documented in books or
>instruction
>> manuals...
>
>
>
>--------------------------- ONElist Sponsor ----------------------------
>
>You can WIN $100 to Amazon.com by starting a new list at ONElist.
>Drawing is held each week through August 20. For details, go to
>http://www.onelist.com/info/onereachsplash3.html
>
>------------------------------------------------------------------------
>

Hi David n All !

A dvm needs to a complete circuit to make a valid measurement, so
consequently a "hanging probes" readout is meaningless .

If you short the terminals together, what happens ?

Measure the voltage of your power supply : does it give the pos and
neg 15V ? Take a fresh battery, should read someting like 1.60 to
1.50 V . All these measurements done on DC V of course . Check the
Ohms range by measuring a resistor . Is the reading about right
(take the tolerance into consideration : 5%, 1%) ? AC can be tested
by measuring your home supply . Careful with those ranges tho :), if
not autoranging that is .

Measuring low Ohm values with an analogue multimeter and an older
battery is good fun tho, the needle will never stabilise :)
(treasuring a 25 jear old Novotest bought new, then ... ;-) )

A useful addition to any kit is some means to temporarily clamp the
dvm inputs to the object . I'm using Hirschmann Kleps for this
purpose, a bit dear, but good quality . Some croc clips could work
too . But watch out for shorts . Also, make sure you have good
contact . The test points should be sharp, so they can pierce
oxidation . The braid on the RG cables is dull, and solders not too
well (lucky for us, they come pre-tinned :) ), this might give
unreliable measurements . Stick the point in a (shiny)solder joint,
should be ok then . With crocs wiggele the jaws a bit, so the teeth
pierce the oxide, Kleps same thing, get a steady readout before you
start tweaking .

A good thing to have are those multicoloured twin croc connects .
These should be checked after some years use though, as the leads
used are generally of inferior quality, and break at the croc, giving
unreliabe results then .

Have been thinking of this before, but making up a few test leads,
say dvm to jack (ground and signal) should be useful too .

Hope some of this helps .


Keep 'em oscillating :)


Hugo
=