Humidity Sensor

Humidity Sensor

A Humidity Sensor reads a humidity (either relative, specific or absolute) depending on the sensor type used. If a sensor is not installed, but the humidity is known, a humidity input can be configured and calibrated with a dial and entered manually. Enabling calculated channels displays all types of humidity (relative, specific and absolute). Definitions of each of these humidity types are as follows:

  • Relative Humidity: The water content of the air as a percentage of the maximum possible amount for the current temperature and pressure.

  • Absolute Humidity: The mass ratio of water to total mass (air and water) within a given volume of air.

  • Specific Humidity: Commonly known as Water Grains (short for water grains per pound of dry air). The mass ratio of water to dry air within a given volume.


Wiring Tab

Options

Humidity Type

Relative (percentage)

Select when the input is a relative humidity sensor.

Specific (water grains)

Select when the input is a specific humidity sensor.

Absolute

Select when the input is an absolute humidity sensor.

Connections

Humidity Input

Select an appropriate input to use for the humidity sensor. An AVI (Analogue Voltage Input) or SPI (Synchronised Pulsed Input) should be used.

AVI

An AVI (Analogue Voltage Input) is suggested.

Pull up

Enables a 1k pull up resistor to 5V.

Typically the pull up should be enabled with any two-wire temperature sensor, and disabled for sensors with their own voltage supply. If the sensor is being shared with another ECU, such as with a piggyback installation with an OEM ECU, then the other ECU will generally include a necessary pull up and this setting should be set to Disabled.

SPI

An SPI (Synchronised Pulsed Input) can be used where there are no available AVIs.

Sensor Type

Set to Hall Effect for all analogue inputs

Pull up

Enables a weak 10k pull up resistor to 5V.

Typically the pull up should be enabled with any two-wire temperature sensor, and disabled for sensors with their own voltage supply. If the sensor is being shared with another ECU, such as with a piggyback installation with an OEM ECU, then the other ECU will generally include a necessary pull up and this setting should be set to Disabled.


Settings Tab

Settings

Enable Calculated Humidity Channels

Enables all three humidity channels. These channels are calculated using barometric pressure (where a barometric pressure sensor is enabled). In the case that a barometric pressure sensor is not available, the pressure at sea level (101.3 kPa) will be used for estimate calculations.

Humidity Channels Update Conditions

The conditions by which the Humidity channels will update. Note: it can take up to 30 seconds for humidity sensors to return an accurate reading.

Select which ECU channel and its conditions will start the timer.

Select

Selection of the ECU channel to be used to update the humidity channels.

Maths

A selection of Equal To, Not Equal To, Greater Than, Less Than, Greater Than Or Equal To, Less Than Or Equal To that is to be used to update the humidity channels.

Value

The value the maths must meet.

Calibration Tab

This allows calibrations for a humidity sensor to be loaded or saved. A number of calibrations come pre-installed with the ESP Software package. If your sensor is not listed, a custom calibration can be created with the data provided by the sensor manufacturer.

From the image above:

1 – Selecting the yellow Open icon on the top left will allow the loading of a pre-configured calibration file.

2 – Selecting the blue Disk icon next to the open icon will allow the saving of your custom calibration file.

Display Tab

Display Maximum

The maximum value that will be displayed by the graphical user interface in the ESP software.


Diagnostics Tab

The settings in this tab allow limits to be set for the detection of either fault conditions, or conditions that could be considered to cause engine damage related to the Humidity Sensor.

Raw Min

When enabled, this allows for the error code P00F2 to be set when the voltage is below the set amount. This is used to detect a short or disconnection with the wiring. If the Engine Protection function is active a DTC Severity level can be selected for this condition if desired. (Default = Disabled)

Raw Max

When enabled, this allows for the error code P00F3 to be set when the voltage is above the set amount. This is used to detect a short or disconnection with the wiring. If the Engine Protection function is active a DTC Severity level can be selected for this condition if desired. (Default = Disabled)

Operating Max

When enabled allows detection of humidity conditions that could indicate a sudden spike in humidity. This will activate the DTC P00F5. If the Engine Protection function is active a DTC Severity level can be selected for this condition if desired. (Default = Disabled)

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