The available evidence supports a 4:1 input-to-output voltage reduction using a 100 kΩ upper resistor and a lower resistor equal to 100/3 kΩ. It does not provide the controller input rating, terminal reference, software scaling parameters, or the sensor's humidity transfer function; confirm those items before installation.
Confirm the Signal and Available Input
The humidity sensor output is 0-10 V. The proposed connection uses AIN4 or AIN5, but the controller configuration is also described as having four analog inputs for resistive sensors.
Calculate the 4:1 Voltage Divider
Connect the 100 kΩ upper resistor between the sensor output and the measurement node. Connect the lower resistor between that node and the sensor signal reference, subject to the controller's reference-wiring requirements. Feed the measurement node to the selected analog input.
U2 = Uin × R2 / (R1 + R2)
R1 = 100 kΩ
R2 = 100 kΩ / 3 ≈ 33.33 kΩ
U2 = Uin × 33.33 / (100 + 33.33) = Uin / 4
At Uin = 10 V, U2 = 2.5 V.| Item | Evidence-based value | Purpose |
|---|---|---|
| Sensor signal | 0-10 V | Humidity transmitter output |
| Upper resistor R1 | 100 kΩ | Sensor output to measurement node |
| Lower resistor R2 | 100/3 kΩ, approximately 33.33 kΩ | Measurement node to signal reference |
| Voltage ratio | U2 = Uin/4 | Reduces 0-10 V to 0-2.5 V |
| Proposed input | AIN4 or AIN5 | Receives the divided voltage |
Configure Scaling Without Guessing the Humidity Range
The evidence specifies voltage but not the humidity range or whether the transmitter response is linear. Use the transmitter datasheet to convert the reconstructed sensor voltage into humidity. If the controller reads the divider output as , the original transmitter voltage is:
Do not assume humidity endpoints or enter an unverified linear scale. The controller's software input type and accepted voltage range are also absent from the evidence.
Wire and Verify the Measurement
- Confirm that the installed transmitter output is 0-10 V and identify its documented signal reference.
- Confirm that AIN4 or AIN5 is available and that its permitted voltage range includes the divider's 0-2.5 V output.
- Install R1 = 100 kΩ and R2 = 100/3 kΩ in the divider arrangement.
- Measure the transmitter voltage and divider-node voltage with the circuit connected. Verify that the node voltage is one quarter of the transmitter voltage; this connected measurement also detects ratio error caused by unknown input loading.
- Apply the transmitter manufacturer's voltage-to-humidity function, then compare the controller indication with an independent humidity reference before enabling the drying sequence.
FAQ
The supplied solution does not use a direct connection. It reduces the signal through a 4:1 divider before feeding AIN4 or AIN5; confirm the controller's input rating before wiring.
What resistor values convert 0-10 V to 0-2.5 V?
Use a 100 kΩ upper resistor and a lower resistor of 100/3 kΩ, approximately 33.33 kΩ. This produces U2 = Uin/4, so 10 V becomes 2.5 V.
How do I scale humidity from the divided analog value?
Then apply the humidity transfer function from the sensor documentation because the humidity range and linearity are not provided here.
