# Linear digital display for commercial alignment readout

G’day,
I have machine using 24VDC and part of the machine has 2 linear alignment axis’ that require a readout display.
Linear axis 1 is Up Down (U/D) , and axis 2 is Left / Right (L/R)

U/D axis has an encoder with output of -16 to +16VDC . each 1VDC needs to indicate 16mm incrementally Example -12VDC = -192mm . Example2 : Zero volts = 0 on the display

L/R axis has an encoder with output of -16 to +16VDC . however each 1VDC needs to indicate 9mm incrementally Example -12VDC = -108mm

Display needs to be able to be read from 2.5metres and have backlit option.

Any help with suggested products for a solution are greatly appreciated.

2 Likes

Hi David
I am a little bit confused here. I think it could probably be a terminology problem.
How is the -16VDC and +16VDC derived from 24V.
What sort of encoder are we talking about. A potentiometer would output a voltage but to get to +/- 16V you would need a + and - supply. Not impossible but I think unlikely…
If you are talking about a rotary encoder this will output 2 sets of pulses 90º apart which are electronically decoded to provide an incrementing or decrementing (depending on direction) count of “events” which could result in a count of - 16 or + 16 but it IS NOT Volts.
How is this +/- 16 displayed now.

Hypothetical scenario: If we had access to this +/- 16 as numbers, an Arduino or RPI could be used to multiply this by 16 or 9 and display the result, assuming you want the display in millimetres.
Be aware though if this method is used the display will have a resolution of 16 or 9 millimetres, that is it will jump in 16 or 9 millimetre steps with nothing in between.

If however the output is in fact a + or - DCVoltage and continuously variable (you don’t say if it is continuous or if it is stepped) a manipulation of ADC numbers should get you down to millimetres at least.

On a commercial level I have seen these displays on milling machines and to a lesser extent on lathes and I think they operate on a similar principle to a vernier caliber although on a larger scale. I have also seen similar for retro fitting add they come in various lengths. Can’t quite remember where now but if I get time I will try to find it again.
Cheers Bob

3 Likes

Hi David.
If you google “digital linear measurement” you will get about 2 million hits which might give you some ideas and indicate what is readily available commercially.
Cheers Bob

1 Like

Thank you Bob,

I’ll have to get the to the bottom of the voltage source first, but will search some more for possible off the shelf device through Google.

Cheers

1 Like

Gday Rob, I managed to find a different reference voltage for the same desired movement…

so the updated parameters:

axis 1 has 0 – 10VDC reference where readout required is 0V = -50 through to 10VDC = 98 , 3.3VDC = 0 .

Is there one product which will convert the analog VDC and can be adapted to a well lit 7segment LCD

1 Like

Hi David
I am getting more confused than ever. Suddenly -16 to +16 has suddenly become 0 to 10. This raises a red flag immediately. How does this happen.

Let us get rid of the word “reference” in this context for a start. A reference is something that other things are measured against, not the variable which now seems to be 0 to 10V.

Is this voltage progression linear. we would have to assume and hope that it is.

-50 to 98 seems a bit strange. Are you sure it couldn’t be -50 to 100. Life could be a bit easier if it was.

What sort of resolution are you after. You haven’t given any clues on that yet.

Exactly what are you trying to measure and what are the extremes and what voltages correspond to those extremes. You indicated in your original post -16V to +16V @ 16mm per volt, That equates to +/- 256mm or a total of 512mm. That seems to have shrunk to 148mm. ???

Some accurate info please with some sort of drawing to go with it would be good.
Cheers Bob
EDIT. I overlooked your last sentence

I think you could do it with an Arduino or similar.

2 Likes