building Voltmeter with 100 probes

Hey all,

I’m looking for a guidance to build a multi probe voltmeter which will be able to take a measure of 100 probes automatically (not at the same time). I’m thinking of getting some controllers and to config them to jump from prob to prob until the last prob. the info of the voltage of each prob will have to be written in the program and the data will have to be saved.

I’m pretty new to this stuff, I know a basic programming in arduino, so don’t be too harsh on me :slight_smile: .

my question is - which model of controllers should I use?
and how to program the controllers to run from prob-line to prob-line.

the main idea is to build a device that will be able to test electronic voltages’ boards from test points to Ground. the minimum test points on each board should be 100.

appreciate the help!
thanks

How fast do you need this to happen?
How accurate the measurements need to be?
What is the expected voltage range you will measure?

Are your voltages less than 5V?

If so, you could use 4067 analog multiplexer chips and the analog inputs of an Arduino. Each chip takes 4 digital outputs to select from among 16 analog inputs. You'll need 7 chips to get 100 (112, actually) inputs. The UNO only has 6 analog inputs so you either need an SMD-based Arduino (Nano, Mini, Fio, Pro or Pro Mini) which has 8 analog inputs or the Arduino MEGA 2560.

25 years ago a reed switch multiplexer was the best you could buy for low level signal measurements. We used a data logger made by Schlumberger. It probably had boards that looked something like the following
http://www.pickeringtest.com/en-au/products/pxi-switching/multiplexer-modules/low-density-mux

johnwasser:
You'll need 7 chips to get 100 (112, actually) inputs. The UNO only has 6 analog inputs so you either need an SMD-based Arduino (Nano, Mini, Fio, Pro or Pro Mini) which has 8 analog inputs or the Arduino MEGA 2560.

Alternatively insert an extra stage of switching, say a 4052 chip between the 4067 chips and four analogue inputs to the Arduino.

What voltage levels do you have in mind? Milivolt signals, possibly AC, of what frequencies?

Thanks for the replays!!

I think of max voltage of 10V, don't think I need more then that. and the measurements should be in milivolts - for example: 1.32V or 8.34V - on DC.

the boards are activated by battery (4.2V DC).

I need to build a plastic pattern to lay the board inside, the pattern will be pinned with gold plated pins which each pin should be a prob that touches the test point in the tested board.

I'm hoping to finish it in two months or more...

I assume that all test points will be a reference from one single ground, but I feel the need to ask. I know what assume can do to a person.

it all starts with the sensors

you can ger resistance based. voltage based and serial.

speed is important.

one school of thought is to use a low count (6ADC) chip with low bit count.

I think you should abandon the idea of using the arduino ADC and get a quality ADC chip, or a few of them
16 bit 16 channel, serial input,,

Avi1234:
I'm hoping to finish it in two months or more...

using my math, it would be easy to do it in more.

dave-in-nj:
I think you should abandon the idea of using the arduino ADC and get a quality ADC chip, or a few of them 16 bit 16 channel, serial input.

There's no need to abandon the idea of using the Arduino ADC (analogue-to-digital convertor) unless higher accuracy is necessary.

Archibald:
There's no need to abandon the idea of using the Arduino ADC (analogue-to-digital convertor) unless higher accuracy is necessary.

higher than what ? no one gave the accuracy or specs.

besides, you MUST have some interface that each individual lead ties into. you HAVE to have some chip.
you have to have 16 ? inputs and then output to the arduino. 16 to one
then the ADC in the arduino brings the 6 into one actual ADC.

or

have a chip that takes the same 16 inputs
has an ADC that is at least 4 times more acurate.
off-loads all the time the ADC requires to read 200 inputs.

dave-in-nj:
higher than what ? no one gave the accuracy or specs.

We know voltages can be up to 10V and that two decimal places are required "for example: 1.32V or 8.34V".

There's no need to abandon the idea of using Arduino analogue inputs unless higher accuracy is needed than the Arduino gives.

yes, one prob needs to be connected to Ground. others to the test points. accuracy is important, the deviance should be as minimum as 0.01V~0.05V.

so where do I start?

if I want to start from scratch - what kind of things should I buy?

I have the arduino Uno, and also the raspberry pi 2.

there is no problem to get a different device - as someone suggested to have a high quality adc chip, where can I get one?