Using 0-10V analog sensor output with rasbery pi

[nayakajit87]

Dear all.
I am new bie to rasberry coding and ckt design. I have 4 analog sensor which gives 0-10v DC output and 4-20mA current. I am looking for ckt that can read these range of Current and voltage parameter with 12bit/16bit resolution.

Some people using
http://ncd.io/raspberry-pi-0-10v-analog-output-module/**broken link removed**
**broken link removed**

**broken link removed**

Is there any schmatic avilable for it

 

[KlausST]

Hi,

It depends on what your input is.
Most properly an ADC....with what decodable analog input voltage range?

For 0..10V just use a resistive voltage divider.
For 4..20mA use a resistor.

Klaus

 

[nayakajit87]

using voltage divider network we can reduce the range , Is there any proven schematic with 12/16 bit resolution using MCP module

 

[KlausST]

Hi,

What's wrong with just two resistors? Too simple?

Klaus

 

[nayakajit87]

i need good resolution . my question is how can i do it.

 

[baileychic]

10V/4095 = 0.00244V
3.3V/4095 = 805.86uV

If Pi is used for ADC reading then you need to scale the 10V to 3.3V.

10V - 3.3V = 6.7V

6.8k and 3.3k will do.

What resolution you want from scaled 3.3V? nano volt, pico volt?

 

[Akanimo]

Hi,

I think the information given about the sensor is not very clear. We have 0-10V and 4-20mA. Is there any relationship between the two? That is to say, does the voltage change with change in the current?

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Please give more info.about the sensor.

 

[KlausST]

Hi,

Resolution has nothing to do with resistors.
Just choose the correct resistor ratio.

Klaus

 

[nayakajit87]

I have schematic for reference . If i wanted to use 0-10V dc reading of analog voltage

Channel-1+ & channel - should be given in range of 0-5V through voltage divider network

vout=(Vs*R2)(R1+R2) -> R1=R2=1K Vs=0-10V from DC output/sensor

If it is 0-30V dc
vout=(Vs*R2)(R1+R2) -> R1=5K R2=10K Vs=0-30V from DC output/sensor

Is it correct ??

 

[KlausST]

Hi,

0..10V is correct

0...30V is wrong.
See it this way:
30V should become 5V.
This is 6:1 ratio.
Voltages behave like the resistance values.
Thus you need 6 "parts" in total where 1 "part" is the output.
--> So "one part" at the lower end and 5 parts at the upper end.

Klaus

Btw: there are more than enough descriptions for this in the internet, even online calculators and explaining videos. Just do an internet search.

 

[baileychic]

Upper resistor 27k
Lower resistor 3.3k

ADC connected across 3.3k.

 

[kripacharya]

Isn't it just FUN trying to teach a newbie about ohm's law.. where he is already working with mircocontrollers and what not without a clue ?
Its just sickening.

you make a 'sketch' (copied of course), and "bootload it" .. no clue what that means. And a cute little led starts blinking.
brilliant. idiotic.

 

[ZASto]

These "new kids on the block" should first learn the basics of electrotechnic, to understand what is Voltage, Current, Power, Resistance, Capacitance, Inductance, and to UNDERSTAND howa Transistor works.
Without transistors there would be no microcontrollers, microprocessors, ...

Unfortunately, arduino is for such kids that are not willing/able to switch the brain ON, just c/p some sketches.

 

[andre_luis]

The simple mention of 4-20mA sensors suggests the action of remote measurement, which by itself would be a strong argument for using galvanic isolation, such as analogue optical couplers. Unfortunately many questions here are posed not contextualized, and probably only throughout the replies is that needed information will arise, by increments.

 

[Gorgon]

0 - 10V and 0(4)-20mA is normal industrial interfaces.
One thing about 4 - 20mA is that many sensors transmit error levels in the 0-4mA range and some also above the 20mA level (22-23mA).

To make a proper interface you should take this into account, and check out the sensors you want to use in the application.

 

[Akanimo]

The OP needs to give more info than there is now.

If a sensor is giving 4-20mA then you can convert it to a 1-5V signal by passing it across a 250-ohm precision resistor. An ADC can then work on this.

 

[Akanimo]

I think we have to differentiate between sensor and transmitter here.

 

[kripacharya]

The OP needs to give more info than there is now.

If a sensor is giving 4-20mA then you can convert it to a 1-5V signal by passing it across a 250-ohm precision resistor. An ADC can then work on this.

I always thought a 4-20 loop was meant for digital signalling in noisy long (I.e. high impedance) loops. This would be converted to voltage of choice at receiver by use of a suitable R, which was not necessarily 'precise'.

What have I missed ??

 

[Akanimo]

...digital signalling...

What have I missed ??

I think that's what you've missed.

 

[kripacharya]

I think that's what you've missed.

No, that's what I was pointing out. It's digital, so what need for an ADC ??

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Oh wait ... haha. My mistake. It IS analog.