K8061 and HIH-4000 from Honeywell

Hi… does anyone have experience with HIH-4000 humidity sensor connected to K8061?
I’ve three sensors… and each one measures a different values… strange thing is that values doesn’t change at all…
I’ve just connected Vcc and GND of sensor to k8061 GND and to an Analog Output set to 5V and sensor out to Analog Inputs.
Could it possible that three sensor are broken? Or i miss something?

If you have a DVM (multimeter), please check the supply voltage of the sensor.
Also you may check the output voltage of the sensor.
What are the output voltages of the sensors.
According to the data sheet should be about 2.4V at 50%RH.

Supply voltage is 5.06V.

I’ve done two different measures.
First one with sensor connected to the board and i’ve got 2.2V. That mean about 46% of humidity. A sensor machine used as reference signs about 65%.
I’ve tried to measure voltage disconnecting sensor from K8061 board and then i’ve got a surprise… i can read 2.8V that mean something near 65% percent.
So it seems that when connected to the board sensor looses voltage… How can i fix this?


There at the analog input of the K8061 is 20k ohm resistive load between the input and GND.
It seems the HIH-4000 humidity sensor’s output is so weak that it can’t produce correct voltage on this kind of resistive load.

There are workarounds.
You may add an unity gain operational amplifier between the humidity sensor output and the input of the K8061.
Or you may remove the resistor array RA4 from the K8061 board. By doing this the 0-10V range will be then 0-5V and the original 0-5V range will be 0-2.5V.
You have to remove the ADx jumper caps when measuring the sensor voltage in the range 0-5V.

I was thinking to such problem.
I’ve got some 74HC4051 here do you think that with all multiplex line to gnd i can use it as a buffer and solve the problem? I know i would waste 7 input lines but this is what i have here… otherwise i’ve got to wait for a 741 like chip.

The 74HC4051 is just a switch. There is no buffer feature inside it.
If you do not like to “break” the card by removing the RA4, you have to use the external operational amplifier.

For example a TLV274 may be a good choice.
If you are not using the analog outputs of the board you may “borrow” one op amp from the K8061 board…

Thanks for the answer…
I wouldn’t touch k8061 board… looking in our chip stock i’ve found:

Which one do you advice?


The LM358 looks the best choice.
You have to connect the +12V to the V+ supply pin of this Op-amp.
At +5V supply you get out only about 3V max.