Using a Panel Meter movement

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use a meter whith known values in a circiut to set your full scale deflection on your VU meter for what your going to measure

what the application. what are you tring to measure

use a meter whith known values in a circiut to set your full scale deflection on your VU meter for what your going to measure

what the application. what are you tring to measure

===== Thanks for the reply. For application, think "guitar tuner". What is being measured is an incoming frequency, relative to a specific reference, so the needle rests in the middle and moves right or left. There's a microcontroller involved, so I assume that I'll be converting that incoming frequency to a voltage to run the meter itself. The meter won't be the only display, but I find that for me, the needle movement is the best visual cue.

Do you know of any sample circuits so I can see what sorts of voltages and currents are normally acceptable for this kind of movement, and how they are normally connected? Or a sample datasheet? These seem harder to find than I expected.

Thanks again, Patrick Keenan

Select the right value of R for the circuit below (R = VCC/(2*Imax), with Imax being the meter's maximum current). It'll give your two-way meter just the motion you want. For a one-way meter use R = VCC/Imax.

VCC + | | .-. | | | | R '-' _ | Vin / \\ | o--------(_/_)-----o \\_/ | | .-. | | | | R '-' | | === GND (created by AACircuit v1.28.6 beta 04/19/05

DC current meter movements vary widely in sensitivity. Usually the cheap ones are 1mA full scale, 'normal' spendy ones are 50uA full scale, and if you have a really interesting antique it could be anything. So you'll have to measure it, and you'll want to start with a source that'll deliver 50uA or less -- a 200k-ohm resistor and a 9V battery will give you about 45uA if my in-the-head calculation is right. Once you see what the reading is at 45uA you can adjust your resistor accordingly to get a good reading.

There's no guarantee that what you have is a DC current meter. You may have an AC current (or voltage) meter, or a DC voltage meter. Without specifications, you'll have to check to see. The most common possibility is a DC current meter, because that's the easiest accurate meter to make.

Thanks to all. These are the kinds of clues I needed.

Patrick Keenan

The web site says they have "100 µA" movements - that's probably 0-100FS for one, and 50-0-50 for the other.

So, take a 1.5V battery, a 10K pot, and a resistor of (1.5V/100 µA) ohms;

wire them like this:

The meter is driven by current. The voltage level powering a microprocessor will be fine, but the current *must* be limited to less than 100 ua, per the page you posted.

Assuming a 5 volt supply, you can use a 2 meg resistor in series to limit the current to no more than 50 uA to give yourself a wide safety margin when testing the meter.

Your actual circuit will dictate how the thing is wired when in use, but in general it will have a fixed and a variable resistance in series. The variable resistance is used to calibrate the full scale meter reading. Something like this:

R1 VR1 +---/\\/\\/\\----/\\/\\/\\ | ^ | | [Source] [Meter] | | +----------------+

Source in the diagram is whatever circuit element drives the meter - transistor, op amp, uprocessor, whatever.

Ed

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how about I just give you guitar tuner schematic so the resisters are already set for your frequency dividing network to match A B C D E F and G would that be better for you the VU meter just measures the voltage difference a good one measures variance in current and Voltage.

"ehsjr"

...... Phil

Perhaps that's in case the 5 volt supply should suddenly spike to 40V?

how about I just give you guitar tuner schematic so the resisters are already set for your frequency dividing network to match A B C D E F and G would that be better for you the VU meter just measures the voltage difference a good one measures variance in current and Voltage. ======

Thanks for the kind offer, but I'm actually doing this for another reason. And the meter is just one of the visual indicators that will be included; the rest I understand but this part I've never used before.

Thanks again. Patrick Keenan

Hello Patrick,

I have a software solution that approaches the idea of what you are doing. I use this for rapid theremin musical note display. It shows the +/- deviation of the displayed note, frequency and wave shape.

• * * *

Christopher

Temecula CA.USA

Thanks! You are correct, of course. My error.

Ed