From 5412411ff1a1c28a340852db50282c38966bb3d4 Mon Sep 17 00:00:00 2001
From: Nathan Spencer <natekspencer@gmail.com>
Date: Tue, 10 Oct 2023 10:29:44 -0600
Subject: [PATCH] Fix vapor pressure

---
 pyweatherflowudp/calc.py  |  5 +++--
 pyweatherflowudp/const.py |  1 +
 tests/test_calc.py        | 26 ++++++++++++++++++++++++--
 tests/test_device.py      |  2 +-
 4 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/pyweatherflowudp/calc.py b/pyweatherflowudp/calc.py
index 21b1ae7..6aefcdc 100644
--- a/pyweatherflowudp/calc.py
+++ b/pyweatherflowudp/calc.py
@@ -9,6 +9,7 @@
     UNIT_KILOGRAMS_PER_CUBIC_METER,
     UNIT_METERS,
     UNIT_MILLIBARS,
+    UNIT_PASCAL,
     UNIT_PERCENT,
     units,
 )
@@ -162,8 +163,8 @@ def vapor_pressure(
                 else 1
             ),
         )
-        * UNIT_MILLIBARS
-    )
+        * UNIT_PASCAL
+    ).to(UNIT_MILLIBARS)
 
 
 def wet_bulb_temperature(
diff --git a/pyweatherflowudp/const.py b/pyweatherflowudp/const.py
index 69ae490..de59adf 100644
--- a/pyweatherflowudp/const.py
+++ b/pyweatherflowudp/const.py
@@ -45,6 +45,7 @@
 UNIT_MILLIMETERS_PER_MINUTE = units.mm / units.min
 UNIT_MILLIMETERS_PER_HOUR = units.mm / units.h
 UNIT_MINUTES = units.min
+UNIT_PASCAL = units.Pa
 UNIT_PERCENT = units.percent
 UNIT_SECONDS = units.sec
 UNIT_VOLTS = units.V
diff --git a/tests/test_calc.py b/tests/test_calc.py
index 46fb309..c65961a 100644
--- a/tests/test_calc.py
+++ b/tests/test_calc.py
@@ -1,6 +1,11 @@
 """Test calculations."""
-from pyweatherflowudp.calc import heat_index
-from pyweatherflowudp.const import UNIT_DEGREES_CELSIUS, UNIT_PERCENT
+from pyweatherflowudp.calc import heat_index, vapor_pressure
+from pyweatherflowudp.const import (
+    UNIT_DEGREES_CELSIUS,
+    UNIT_MILLIBARS,
+    UNIT_PERCENT,
+    units,
+)
 
 
 def test_heat_index() -> None:
@@ -16,3 +21,20 @@ def test_heat_index() -> None:
 
     temp_degrees = 10 * UNIT_DEGREES_CELSIUS
     assert heat_index(temp_degrees, relative_humidity) is None
+
+
+def test_vapor_pressure() -> None:
+    """Test the vapor_pressure calculations."""
+    temp_degrees = 71.7 * units.degF
+    relative_humidity = 55.17 * UNIT_PERCENT
+
+    vap_pressure = vapor_pressure(temp_degrees, relative_humidity)
+    assert round(vap_pressure, 3) == 14.641 * UNIT_MILLIBARS
+    assert round(vap_pressure.to(units.kPa), 3) == 1.464 * units.kPa
+
+    temp_degrees = 60.0 * units.degF
+    relative_humidity = 41.93 * UNIT_PERCENT
+
+    vap_pressure = vapor_pressure(temp_degrees, relative_humidity)
+    assert round(vap_pressure, 3) == 7.411 * UNIT_MILLIBARS
+    assert round(vap_pressure.to(units.kPa), 3) == 0.741 * units.kPa
diff --git a/tests/test_device.py b/tests/test_device.py
index eaf71a7..bb39268 100644
--- a/tests/test_device.py
+++ b/tests/test_device.py
@@ -195,7 +195,7 @@ def load_complete(event):
     assert round(device.dew_point_temperature, 5) == 11.52825 * UNIT_DEGREES_CELSIUS
     assert device.feels_like_temperature == 22.37 * UNIT_DEGREES_CELSIUS
     assert device.heat_index is None
-    assert round(device.vapor_pressure, 5) == 1359.55045 * UNIT_MILLIBARS
+    assert round(device.vapor_pressure, 5) == 13.59550 * UNIT_MILLIBARS
     assert round(device.wet_bulb_temperature, 5) == 15.77886 * UNIT_DEGREES_CELSIUS
     assert device.wind_chill_temperature is None