Resolution of an Analog Multiplexer?

Hello everybody,

i want to monitor a lot, i really mean a LOOOT of Analog inputs in a Arduino Nano,
but i dont want to buy like 12x "ADS1115 4 Channel 16 Bit I2C Module"
So i stomble about this Product, which should read also the analog voltage on the pins, but i need to know in which resolution (like 8,10,12,16... bit).

Does anyone know which they have, i cant find an answer anywhere in the internet...

  • lynes

(The product)

Are you sure that the board can actually read voltages ?

The chip that it uses is described as an "analogue switch"

The CD74HC4067 and CD74HCT4067 devices are digitally
controlled analog switches

i though it because of this video on Youtube:

and this:

Website with more details:
https://bildr.org/page/18/

Resolution does not apply to multiplexers.
It is NOT an A to D converter !
It’s a ROTARY SWITCH ! (and an ANALOG one at that)
That means ANALOG IN , ANALOG OUT

Does a SWITCH have a resolution (4,8,16 etc)?
What is the definition of ‘resolution’ ?
"
The resolution of an A/D converter is defined as the smallest change in the value of an input signal that changes the value of the digital output by one count. For an ideal A/D converter, the transfer function is a staircase with a step width equal to the resolution."

Does an ANALOG MULTIPLEXOR have a DIGITAL OUTPUT ?

Think about that.
(FYI, that’s why you can’t find it because
there is no such spec for a MUX.
It has a propagation delay (15nS).

@UK_Bob,
That answers your question. It doesn’t ‘read’
voltages, it passes them. Just think of it
as an invisible switch , either on or off, ( but in
this case , rotating)

@OP,
You should change your post title to:
‘No Such Number’

Hi,
It is not an AtoD converter multiplexer, which I think you are looking for.
In other word you are looking for an ADS1115 with more than 4 inputs.
Something like this;
https://www.iascaled.com/store/ARD-LTC2499

Try google arduino adc shield

Tom.. :slight_smile:

Thank you all,
I wasn't sure how these chips could read analog inputs either, but I saw a lot of pictures with each potentiometer and sensors attached to the pins.
So thanks to you, now I know what I'm not going to buy ^^

The 4067 is an analog switch, 16 channel in
to one output, or one input to 16 outputs.
(It is bi-directional.) The ON resistance
is 200 ohms from in- to out-. One channel
at a time, of course.
Herb

Whilst it might be fun to have lots of analog inputs - think what you will be doing with them and all that data you will get .

"I wasn't sure how these chips could read analog inputs either, but I saw a lot of pictures with each potentiometer and sensors attached to the pins."

As others have said, this multiplex chip just passes the analog input to the board analog input pin and the board handles the reading of the input. These types of chips can themselves can be multiplexed to have a lot of analog inputs to a single A0 pin if desired. Below is a different multiplex chip, but shows the idea of multiple chips.

Just FYI - Analog chips do have resolution limitations (but of course it's not measured in "bits'). Usually noise is the limiting factor but it could also introduce a DC offset or other "distortions". i.e. VHS tape has lower resolution than DVD and vinyl records have lower resolution than CDs, etc.

I'd assume the analog chip is better than the Arduino's 10-bit ADC (with the default 5V reference)..

And, the Arduino's ATmega chip has only one internal ADC with an internal multiplexer for multiple analog input pins.

Analog chips do have resolution limitations (but of course it's not measured in "bits'). Usually noise is the limiting factor but it could also introduce a DC offset or other "distortions"

I submit that the term 'resolution' cannot be used because by definition it relates to bits.

The resolution of an A/D converter is defined as the smallest change in the value of an input signal that changes the value of the digital output by one count. For an ideal A/D converter, the transfer function is a staircase with a step width equal to the resolution

You can say the signal to noise ratio or Frequency Response at -3db or ON Resistance are limiting factors but
it is not really correct to use the term 'Resolution', ESPECIALLY with a Newbie because it is hard enough for
them to understand the other three specs mentioned let alone how 'Resolution' can apply without bits. This
is a discussion for experienced electronics professionals who understand it is possible (via Ohm Law's) to calculate
the voltage drop of a 1mA analog signal passing through a 270 Ohm On resistance by V = IR=0.001270= 0.270V (270mV) , which , we all know is 270/(5/1023) = 55.242 arduino analog counts , (which you don't
really need to calculate if you already know the voltage drop is 270mV. You can simply say it is a 5% signal loss
that can easily be compensated for by software code that multiplies the calculated voltage by 1.05 to obtain
the original signal voltage before it passed through the multiplexor. Frankly , I would say you would be hard
pressed to find an engineer who would say a 5% loss is not 'negligible', and may be ignored. Bottom line is
a 5V signal will be read as 4.75V. Is this a problem for the OP ? Only he can say. I wouldn't worry about it.
If it did matter it would be a simple matter to insert an LT1215 op amp non-inverting amplifier
[EDIT] (to correct resistor values)

with a 10k input resistor and a 500 ohm feedback resistor, resulting in a gain(A) of Vo = Vin (1+(Rf/Rin) = 4.75(1 + 0.05)= 4.75*(1.05) = 5V.

End of story.

"If it did matter it would be a simple matter to insert an LT1215 op amp non-inverting amplifier with a 9.5k
input resistor and a 10k feedback resistor, resulting in a gain(A) of Vo = Vin (1+(Rf/Rin) = 4.75(1.05)=5V.

What is the % tolerance of those components?

lynes:
So thanks to you, now I know what I'm not going to buy ^^

Sure about that?

WHAT are you planning to measure.
The 10-bit ratiometric A/D of the Arduino is ok for ratiometric sensors (pots, ADS712, etc.), but unsuitable for voltage sources. The muxers can also connect to ADS1115 chips, if you have absolute/voltage sensors.
There is no one-fits-all. Tell us more if you want proper advice.
Leo..

What is the % tolerance of those components?

Well, now that you mention it they would need to be 1%.

Note: Non-Inverting Amplifier resistor values changed to:
Rin = 10k/1%
Rf = 500 ohm/1%

"Well, now that you mention it they would need to be 1%."

That would seem to indicate that in the end result that resolution of anything being measured would be no better than 1%. Real world the OP probably just needs to measure the analog signal source with a good multimeter and compare that to the reading the board puts out and see how things stand.

"no better than 1%" ?
Are you kidding me ?
You say that like there's something wrong
with 99% accuracy.

“You say that like there’s something wrong
with 99% accuracy.”

No, I think I just stated a fact. Are you saying one can get .5% or .05% accuracy using 1% components?

No, I think I just stated a fact. Are you saying one can get .5% or .05% accuracy using 1% components?

No, I'm saying the tolerence is +/- 1% with 1% components. I never suggested anything less than 1%,
but that means the signal amplitude is 99% of input signal +/- 1% , which , in my book is still pretty good,
which , for some reason, you are reluctant to admit.

"No, I'm saying the tolerence is +/- 1% with 1% components. I never suggested anything less than 1%,
but that means the signal amplitude is 99% of input signal +/- 1% , which , in my book is still pretty good,
which , for some reason, you are reluctant to admit."

No where have I posted an issue with true 99% accuracy on anything. Not sure where you came up with that. As they say, garbage in, garbage out, usually based on the least accurate component. Kind of like multiplying 6.3 times 2.145 and expecting the result to be accurate to three decimal places. A chain strength is often keyed to the weakest link.