[SOLVED] Measuring current output from sensor to PIC ADC

[lockman_akim]

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

 

[KlausST]

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

 

[lockman_akim]

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

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?

 

[KlausST]

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

 

[lockman_akim]

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

thanks a lot