Digital signal of Relative Humidity sensor to analog input in data logger

Using Arduino Sensors
1

Hello,

I am new to electronics, so this question might be easy for expert her(or may not be that simple - I don't know).

So, my situation is, I have to measure relative humidity and temperature inside a concrete. For that i will use Sensirion SHT75 sensor (Datasheet). The signal is digital from this sensor. However, my data logging device has single ended analog channel input.

Is there a way I can measure the relative humidity from arduino and send the analog output from arduino to my data logger ?

Thanks in advance. :slight_smile:
S.

2

Sachindra:
Hello,

I am new to electronics, so this question might be easy for expert her(or may not be that simple - I don't know).

So, my situation is, I have to measure relative humidity and temperature inside a concrete. For that i will use Sensirion SHT75 sensor (Datasheet). The signal is digital from this sensor. However, my data logging device has single ended analog channel input.

Is there a way I can measure the relative humidity from arduino and send the analog output from arduino to my data logger ?

Thanks in advance. :slight_smile:
S.

Yes you can,

You will have to add a DAC to generate the Analog values. Either a simple R2R ladder or an actual DAC converter.

That Sensor uses a modified I2C protocol, you will have to write your own protocol library, the standard Wire.h will not work.

What is the resolution of your Logger, that sensor has 12bit temp and 14bit relative humidity.

Chuck.

3

Less work to choose an analog sensor. eg like the HIH4000-family
(several others out there)

4

@knut_ny
True. But, we have experience of using SHT75 in concrete. As this is a part of a big project, we would not want to change it right now-- although they are pretty similar.

@Chucktodd

The resolution of logger is 16 bit.

As the sensor gives relative humidity of 14 bit, can we just scale the reading of RH as an analog output? The reading of RH would vary from 0 to 100%. Can we hook up the sensors to the digital pins of Arduino to read the RH values. Then send those RH values to analog output.

RH --> Analog
0 --> 0
100 --> 16383 (for 14 bit)

So,
AnalogValue = 16383/100 * RHreading

Can I simply use this function and analogWrite on the analog pin and connect it to the logger ? Also, for temperature it would be 12bit so 4095 instead of 16383?

Any response will be highly appreciated.

Thanks,
S

5

Sachindra:
@Chucktodd

The resolution of logger is 16 bit.

As the sensor gives relative humidity of 14 bit, can we just scale the reading of RH as an analog output? The reading of RH would vary from 0 to 100%. Can we hook up the sensors to the digital pins of Arduino to read the RH values. Then send those RH values to analog output.

RH --> Analog
0 --> 0
100 --> 16383 (for 14 bit)

So,
AnalogValue = 16383/100 * RHreading

Can I simply use this function and analogWrite on the analog pin and connect it to the logger ? Also, for temperature it would be 12bit so 4095 instead of 16383?

Any response will be highly appreciated.

Thanks,
S

Analog write just produces a PWM square wave, you can get a low res simulated analog value by connecting a resistor and capacitor to the PWM pin, But it will be a low res signal, approx 7-6bit.

This Sparkfun 12bit DAC module would be a much better choice.

To actually produce a 14 or 16bit DAC, you will have to build your own circuit, using something like a AD5662 DAC converter.

Chuck.

6

UNO + DAC vs Arduino DUE ?