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[SOLVED] Measuring current output from sensor to PIC ADC

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lockman_akim

lockman_akim

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Hi,

how can i measure the output of the sensor which rated 4 to 20mA with PIC ADC?
how the circuit gonna be in between the sensor output and the PIC ADC pin?

Thanks
 

Hi,

Not much information....

It depends on your adc input range.
If it is 0...3.0V then use a simple 120 Ohms resistor.
With 4mA this gives 120 Ohms x 4mA = 480mV.
With 20mA it gives 2.4V
A 10 uF capacitor in parallel to resistor avoids noise in adc readings...


Hope this helps.
Klaus
 
KlausST said:
Hi,

Not much information....

It depends on your adc input range.
If it is 0...3.0V then use a simple 120 Ohms resistor.
With 4mA this gives 120 Ohms x 4mA = 480mV.
With 20mA it gives 2.4V
A 10 uF capacitor in parallel to resistor avoids noise in adc readings...


Hope this helps.
Klaus
Click to expand...

lets say its a constant voltage from the sensor 5V.
and i want the range from 0 to 5V. can this schematic to be apply in my design?

edaboard.png
 

Hi,

I can't imagine a sensor with constant output voltage = 5V
If you know it is 5V then you don't have to measure it.

I rely on 4..20mA sensor output.
With 5V adc input range you need a resistor of less than 5V / 20mA = 250 ohms.

use 220 Ohms. One side to gnd. The other from sensor output and to ADC input..
Capacitor in parallel to this resistor.
For protection use two diodes

Gnd ----|>|--- adc ---|>|--- Vcc.

Hope this helps
Klaus

One side
 
KlausST said:
Hi,

I can't imagine a sensor with constant output voltage = 5V
If you know it is 5V then you don't have to measure it.

I rely on 4..20mA sensor output.
With 5V adc input range you need a resistor of less than 5V / 20mA = 250 ohms.

use 220 Ohms. One side to gnd. The other from sensor output and to ADC input..
Capacitor in parallel to this resistor.
For protection use two diodes

Gnd ----|>|--- adc ---|>|--- Vcc.

Hope this helps
Klaus

One side
Click to expand...

thanks a lot
 

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