Analog Meters

[roger]

How many still carry an analog meter in their meter arsenal?

With the sensitivity and false readings a DVM can give, I think it is a must to have something at your disposal (besides a solenoid type indicator) that can see the actual voltage.

Roger

 

[stew]

Re: Analog Meters

I still carray an analog and find it very usefull for checking diodes and capacitors.I like to see the meter swing on both these applications.

 

[iwire]

Re: Analog Meters

I keep a Simpson 260.

Just this morning I was in a plaza parking lot troubleshooting 480 volt lighting.

Fluke T-5 said 195 volts, Wiggys said 0 volts.

Wiggys where correct.

[ March 27, 2004, 08:11 PM: Message edited by: iwire ]

 

[electricman2]

Re: Analog Meters

Simpson 260 here too. Mine is probably 25 years old or so. No picture though.

 

[iwire]

Re: Analog Meters

Originally posted by electricman2:
No picture though.

That's OK I "Googled" that picture.

 

[cs409]

Re: Analog Meters

i have a Sim 26.......it use to be a Simpson 260 but it got rubbed a bit......i like the analog amp, volt and of course wiggys.....some times i feel like I love Lucy will come in on the fluke .........2cents worth.

 

[zekeman]

Re: Analog Meters

Since the main problem with DVM's is the false voltage reading you get because of their very high input impedances, why don't the manufacturers put out DVM's with adjustable input impedances equivalent to the 20,000 ohms per volt full scale of the good analogs- or do they?

 

[hurk27]

Re: Analog Meters

I just put a small light bulb across my leads when I need to load the circuit in question when taking a voltage reading. I have a pigtail light socket with long leads with clips on the end. This way I don't have to carry so many meters.

 

[hbiss]

Re: Analog Meters

I think Wayne has the right idea. If the accuracy of a Wiggy or the newer electronic versions that load the measurement properly isn't good enough place a load across your DVM leads.

I found along time ago that even the best of analog meters just won't hold up for very long rattling around in the truck. Also, even these can have a high input impedance though not as high as is possible with a DMM.

The only analog meter I have is a Simpson "kick meter" I use for telecom work. I got it with a nice padded case and never had a problem with it, though it's designed for rough use.

-Hal

[ March 28, 2004, 09:56 PM: Message edited by: hbiss ]

 

[al hildenbrand]

Re: Analog Meters

) forget to change the scale back from Ohms before contacting a live circuit, I'm not out much. I keep two on the truck.

A modest input impedance d'Arsonval analog meter smoothes out the "jitter" of the step-wise digital world

 

[brian john]

Re: Analog Meters

Simpson 260 is part of our test equipment. When phasing a generator to utility nothing like the swing of the needle.

 

[karl riley]

Re: Analog Meters

Roger, though I like to watch a needle too, please explain how high input impedance results in "false" voltage readings. That needs explaining.

Karl

 

[karl riley]

Re: Analog Meters

Roger, though I like to watch a needle too, please explain how high input impedance results in "false" voltage readings. That needs explaining.

Karl

 

[roger]

Re: Analog Meters

Karl, I guess "Phantom voltages" would have been a better term.

With high impedance, the meter is looking at a no load condition which lets it almost read air.
Roger

[ March 29, 2004, 07:57 PM: Message edited by: roger ]

 

[Ed MacLaren]

Re: Analog Meters

First, a bit of basic theory for any readers who may not be familiar with voltmeter history.

A voltmeter connected to a circuit is in parallel with the load, and acts like an additional load. The more current a voltmeter draws from the circuit under test, the more the measured voltage will "sag" under the loading effect of the meter.

The first high impedance voltmeter, the VTVM (vacuum tube volt meter) was developed for use on electronic circuits. The old basic analog meter movement required up to a milliamp to drive the pointer to full scale. If this was used to measure voltage in an electronic circuit where the normal current was only 1 mA, it would double the load the source must deliver, pulling down the source voltage.

The modern digital voltmeter has a very high input impedance, meaning that it draws almost zero current from the circuit under test. This way, there will be little, if any, "impact" on the circuit as the voltage is being measured.

In other words, it takes a very tiny current input to the meter to operate the display.

There is no need for such a meter for use on building wiring circuits. The old 1000 ohm-per-volt analog meter actually does a better job.

please explain how high input impedance results in "false" voltage readings. That needs explaining.

This is how I view it.

A radio amplifies the energy induced into the antenna, to a value high enough to drive a speaker or headphones.

Think of a building wiring system as an antenna, and your high-impedance digital meter as an amplifier (which it is) that can amplify the induced energy to a value high enough to produce a reading, even if the circuit supply is shut off.

Ed

[ March 29, 2004, 10:22 PM: Message edited by: Ed MacLaren ]

 

[karl riley]

Re: Analog Meters

Ed, I understand the first part of your post, which agrees that the high impedance of the digital meter does not distort the voltage or drag it down with its parallel impedance.

But then you say that the meter is amplifying the voltage. That I don't comprehend. Please explain. I have never seen an amplified voltage when using my digitals. And I have never seen a "phantom" voltage when the common is to ground. Of course if you are measuring in air, you may be measuring the electric field, and there are ways to calibrate this.

My understanding is that analog meters tell you if the voltage you are measuring has amps behind it. Since I deal in amps as well as in tenths of milliamps, my digital meter reads true in both cases. I use a clamp-on to read amps.

Karl

 

[roger]

Re: Analog Meters

Karl, for some more discussion on this go here

Roger

 

[Ed MacLaren]

Re: Analog Meters

you say that the meter is amplifying the voltage. That I don't comprehend. Please explain.

I guess the point I was trying to make is how little current input it would take to drive the display.

I agree that there is no such thing as a false or phantom voltage reading. If there is a voltage reading on a properly functioning meter, there must be a current, however small, flowing into the meter, and therefore a voltage to force it.

Ed

 

[hurk27]

Re: Analog Meters

I think what most here is refering to (pantom voltage) is the voltage induced into a wire that has no load connection or ground termination, and that wire is ran in a raceway with other wires carrying current. This voltage reading when trouble shooting will allow you to think there is voltage on a wire but when you throw the light switch the light still wont go on. this is why a loaded meter like a coil driven wiggy is a must for trouble shooting.