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Hello stackexchange friends,

I am looking to purchase this relative humidity/temperature sensor.

http://www.michell.com/us/documents/PCMini52_97176_US_Datasheet_V5-1.pdf

It has 0-5 VDC output option (as well as 0-1 and 0-10), which is perfect for my application because I am using an Arduino Mega to measure my other VDC output sensors.

So, if you look at the datasheet, this sensor has an M8 connector. Would I be able to use an M8 connector with the ends stripped, and then connect those ends to my Arduino?

I understand that the wire sheath protects from EMI and such, so I wouldn't strip it until the very end.

I've never used an M8 connector before, so please let me know if I need to pull out the dunce hat!:)

Thank you for your time.

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  • \$\begingroup\$ Are you aware that you can't power the sensor from your Mega's +5 V? For 0 to 5 V out it needs a much higher supply voltage. \$\endgroup\$
    – Transistor
    Aug 4 '17 at 6:01
  • \$\begingroup\$ Yes, I am currently powering my sensors with a power supply - not the Arduino. I meant to say I will be connecting my signal output signals to the Arduion. \$\endgroup\$
    – L. Paw
    Aug 4 '17 at 14:59
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Since the sensor outputs an analog voltage and not a high frequency signal, EMI is not a major concern. And since the sensor can be configured to output 0-5V, then connecting it directly to the Arduino should work just fine.

In general, the type of connector is of lower concern than ensuring that the voltages are compatible. This sensor simply requires four wires, and it doesn't matter what type of connector they are housed in.

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    \$\begingroup\$ That's what I assumed, so I'm glad to hear that is okay. I figured as long as it wasn't a serial communication type of connection it should be fine. thanks! \$\endgroup\$
    – L. Paw
    Aug 4 '17 at 15:02
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I suggest putting some series resistance on the ADC input and a capacitor to ground for each input. The sensor has its own supply so it's possible the sensor could output more than Vcc on the Ardunio's MCU, which would cause current to flow into the protection networks on the chip.

Maybe something like 4K99 and 100nF on each input, which forms a low pass filter with a cutoff of a few hundred Hz (since RH and temperature typically change much more slowly than that, it won't affect your signals). The ADC is pretty crude (10-bit) and uses the 5V supply as a reference so it's not a very good ADC, but should be fine for RH. For temperature it might be off a bit- if the supply is off by 3% (worst case for AMS1117) you will get 3°C error at 100°C which is a significant degradation of the sensor accuracy. More likely it will be more like +/-0.5°C typically at room temperature, but that's still much worse than the sensor accuracy. You could calibrate some of the error out.

schematic

simulate this circuit – Schematic created using CircuitLab

You can find a mating connector for the M8 say bulkhead with pigtail leads or whatever suits your application best. Here is a catalog from one manufacturer, there are others you can look up.

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  • \$\begingroup\$ Thanks! I have used a low pass filter for my other sensors which definitely helped with precision. I appreciate your thorough answer. \$\endgroup\$
    – L. Paw
    Aug 4 '17 at 15:01

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