Serial monitor not reading my long-distance sensor

Hello everyone, I'm new here (both to arduino programming and coding generally) , I just hooked up a pressure sensor to my Arduino Pro mini and got readings (0.67 Volts) on the serial monitor when there isn't any pressure while the voltage goes up as I apply pneumatic pressure to the sensor, I was satisfied with my progress so far. But as I connected a much longer wire between the sensor and the controller the voltage on the serial monitor dipped to 0.42 Volts and has refused going up when I apply pressure to the sensor, please how do I solve this issue? I would be really grateful if I could get a quick reply as it is urgent.

If it were urgent, you would have supplied details to help us to help you.

The sensor is a 6-pin CF sensor , 3 pins (gnd, 5V and analog output). Connecting them directly to the Arduino Pro mini and measuring the analog output to ground gives 4.98 V. so I connected a 10k resistor in parallel with the analog output and used the math formular ((5./1023.) * analogRead(A0)). I got 0.67 volts on the serial monitor when no pressure is applied, this value also corresponded with my multimeter value so I knew it was working fine.Now I need the sensor to be more than 20metres away from the controller but the value is no longer changing on the serial monitor rather it keeps showing 0.42 volts no matter how much pressure I apply

I suspect too high voltage drop in the 20 meters of wire. What gage of wire are you using? When the "5V" power gets to the CF Sensor, is it still 5V?

What do you mean "so I connected a 10k resistor in parallel with the analog output"? Why would you do that?

I am using a 1.5mm² (3-core) , the voltage reads 4.98 V right on the sensor terminals. Before I connected the 20m cable, I hooked up the sensor directly to the analog pin on the controller directly but didn't get any reading on the serial monitor, then I connected a 10k resistor in parallel with the analog pin to ground and got readings on the serial monitor

@johnwasser here is a picture of the sensor, I also uploaded the schematic of my arrangement to the Arduino

Could the problem be resolved if I take out the 10k Ohm resistor? Secondly, if the resistor is the problem how come it is working properly when the sensor is hooked up without the 20metre 1.5mm² cable?

Hi @edichumo

That 10k resistor is acting like a pull-down resistor. So the voltage stays at gnd when the sensor isn't outputting anything instead of floating. Do you know anymore specs about the sensor? Data sheet possibly or model number?

Here is a screenshot of the sensor and some details

http://www.cfsensor.com/proinfo/9.html

That's the link to the datasheet

In the data sheet it explains the wiring and has a schematic. It also says that the output voltage is 0.5V - 4.5V and -100kpa - 1500kpa.

Ohhhh....I guess I overlooked the circuit diagram. Thanks alot, I'll have to set up my circuit again and try it out. Thanks for your help

:+1:

Unless one of the wires is broken or shorted to another, I can't see any reason for the output signal to be unresponsive. I recommend you remove the 10k pull-up since it would be fighting the 5k pull-down built into the module.

Which exact model number do you have? The part after the XGZP6847A part indicates the pressure range and polarity.

The output should be 0.5V at the low end, 2.5V at mid range, and 4.5 at the high end. That means 0.67 volts is a pressure close to the low end of the scale.

Exactly! I get 0.67 Volts on serial monitor when I connect the sensor directly to the controller without the 20metre cable. I have checked the cable for breakages using my multimeter's continuity mode and found none as there is continuity from end to end and none between each core.

So you are basically saying , the circuitry on the right of this picture is inbuilt?
If that is so, then I guess I have to try it again without the 10k Ohm resistor I used as a pull-down .

Hi,

@edichumo, that "Circuit Diagram" is correct. That is the external circuitry needed. This is the internal circuitry:

In order to have the sensor work, you need that external circuitry. It wouldn't make much sense if that was internal either because it just has a 5V zener over voltage protection diode, a smoothing capacitor, and a 5k pull-up resistor.
Definitely remove any external circuitry you have already put, and retry it with the components in the data-sheet. Check back when you have tried it or have more info.

@johnwasser you are right, the 10k resistor was the problem. The circuit is working fine now. Thank you for your assistance