# programming alpha/num digital display

Joined Oct 4, 2014
5
Hi, I am a new member. I am working on a project and would like to substitute letters for numbers on a DC volt meter and keep the same letters when I change the polarity. It is a beautiful blue sky fall day in the Adirondacks of NY. Thanks, Bill

#### MrCarlos

Joined Jan 2, 2010
400

So your DC volt meter shows you the result of a measurement with letters.
You want to show those letters into numbers.
Which letters of the alphabet shows your voltmeter?
From A to Z? Or only from A La F?

If only shows the letters from A to F is relatively easy to change those letters to numbers.
Adding 6 to the letter it appears.
A = 1010 + 0110 = 1 0000
B = 1011 + 0110 = 1 0001
C = 1100 + 0110 = 1 0010
D = 1101 + 0110 = 1 0011
E = 1110 + 0110 = 1 0100
F = 1111 + 0110 = 1 0101
The first column of the Result are the units of tens, the last 4 digits are the units: 0, 1, 2, 3, 4 and 5.
But if your DC meter shows a reading as follows: 1E8, then it is another story
So some data is missing in your approach.

Joined Oct 4, 2014
5
Hi MrCarlos,

Thank you. I am messaging Fran52, also. Again, let me say that I am not even a novice in electronics. I have been looking for a manufacturer to produce a volt meter but they do not want to step out of their boxes.

I used the letter/number example to make it easier to understand, but, you and Fran understood immediately and moved way ahead.

So, what I want is to have a meter that will have 5 = 0, 6 = 1, 7 = 2, 8 = 3, etc. So that when I input 1320 mV the display will be 6875. And, and this is key, when I switch the polarity the display will be - 6875. Just as 1320 would be - 1320.

I guess what I need a way to describe to a manufacturer what I need in electronics language, to see if they are interested in a new product.

Where should I go from here?

#### MrChips

Joined Oct 2, 2009
27,163
Can you provide a conversion table showing what the meter puts out and what you want displayed instead?

Joined Oct 4, 2014
5
Good Evening MrChips and all,

Let me describe my system. I have two power sources "A" and "B", each at 1 amp with varying voltage from 0 to 4000 mV DC.

Source "A" is connected to meter "a," and Source "B" is connected to meter "b." (Good meter accuracy and sensitivity are necessary.)

Meter "a" is a regular meter. So, when source "A" produces 1320 mV, meter "a" will display 1320. (The + sign does not show, of course.) When I switch the polarity the display becomes - 1320.

(While "A" will always be attached to meter "a," and "B" will always be attached to "b," I will not be able to tell which is which because I will only be able to see the meter displays. And further, it is imperative that the meters are not labeled.)

Therefore, with meter "b," in order to know that it is getting its power from source "B," I have to change the display.

So, when in a normal meter you would see a zero, with meter "b" you would see a five. And, when you would normally see a one, with meter "b" you would see a six.

5 = 0, 6 = 1, 7 = 2, 8 = 3, 9 = 4, 0 = 5, 1 = 6, 2 = 7, 3 = 8, and 4 = 9

So, when source "B" produces 1320 mV, meter "b" will display 6875.

That is it.

What do you think?

The critical part is when I change polarity. Meter "b" must display exactly - 6875.

#### MrChips

Joined Oct 2, 2009
27,163
it is imperative that the meters are not labeled.
This is the part I don't understand. Why can't you paint one meter red and the other blue, for example?
Or one meter with red LEDs and the other green?

#### MrCarlos

Joined Jan 2, 2010
400

You can just add 5 to source B.
If Source B changes polarity, add -5.

#### mcgyvr

Joined Oct 15, 2009
5,394
This is the part I don't understand. Why can't you paint one meter red and the other blue, for example?
Or one meter with red LEDs and the other green?
um yeah..
+1...
sounds like someone has come up with some wacky scheme to over complicate what should be a simple problem/solution.

Its not that the manufacturers don't want to "step out of the boxes".. its that you are making a goofy request and they can tell you don't know what you are doing. no offense.
why not really explain EXACTLY what you are doing and we can help come up with a much better solution.

Joined Oct 4, 2014
5
Good Afternoon,

Please understand that it would be inappropriate to explain why I need meter "b" to meet very specific criteria. You folks are extremely generous in offering your input. But, if I am willing to pay a manufacturer to build a product, why would they fight me? If I could do this myself, it still would be foolish because of tooling and economies of scale.

Now, if you are telling me what I want cannot be done, while that would not make sense, I would accept it, thank you, and move to my next option.

Please don't give up so fast.

#### MrChips

Joined Oct 2, 2009
27,163
We're only trying to help. I have learned a long time ago it pays to look outside the box.

What you want can be done. But I bet there are other solutions still to be considered.
If you can explain, even via PM, why you want to do it your way it would help a lot. Otherwise count me out.

Joined Oct 4, 2014
5
OK. I do not know what PM means. So let me try this example: I have two power sources "A" and "B" each supplying DC voltage of 0 - 4000 mV. YOU are very familiar with "A" and "B." When I communicate the meter readings from "A" or "B" to you , I want it to be as simple as possible, so that you will never make a mistake in interpreting which numbers are from "A" and which from "B", even if you tell 20 people and they tell 20 people.

Thus the code.

Now, you are correct. It does not have to be as I envision. It just has to be that when I show you a four number set, without any other information, you will know immediately, without ambiguity, whether it is for "A" or "B." My way appears to be the safest for scientific use.

Thank you for giving me another opportunity to explain. While I haven't explained what my project is, or how this voltmeter component will fit in, the principle and end result is exactly as described.

Also, if it is required for me to be more explicit about my project in order to participate, then this has been my error and I apologize for wasting your time.

I hope this conversation continues.

#### MrChips

Joined Oct 2, 2009
27,163
How many significant figures do you need?
If you can spare the least significant digit, you can alter the last digit so that one shows 0, for example, and the other shows some other numeral.

Or one shows the correct value and the other shows "A".