Improve gas_ceiling scaling

Represent int kΩ rather than raw Ω for easier values.

README.md

@@ -63,13 +63,15 @@ but can be done if desired.
 
 The AQ (air quality) calculation from the BME680 requires a "maximum"/ceiling
 threshold for the gas resistance value in clean air after some operation
-time. The value defaults to 200,000 to provide an initial baseline, but
-should be calibrated manually by:
+time. The value defaults to 200 kΩ to provide an initial baseline, but
+should be calibrated manually after setup as each sensor is different:
 
-1. Turning on the Supersensor in a known-clean environment (e.g. a sealed
+1. Turn on the Supersensor in a known-clean environment (e.g. a sealed clean
    container in fresh air).
-2. Leave the sensor on for 4-6 hours to burn in the sensor.
-3. Setting this to the maximum value of the Gas Resistance sensor.
+2. Leave the sensor on for 4-6 hours to burn in.
+3. Record the maximum Gas Resistance value (in Ω) and round up to the nearest
+   5,000-10,000 or so (e.g. 96,938 => 100,000).
+4. Divide the rounded maximum Gas Resistance value by 1000 to get the kΩ value.
 
 This value will then define what "100% air quality" represents, and the
 Supersensor can then be moved to its normal operating location.

supersensor.yaml

@@ -60,7 +60,7 @@ globals:
   - id: gas_ceiling
     type: int
     restore_value: yes
-    initial_value: "200000"
+    initial_value: "200"
 
   - id: pir_hold_time
     type: int
@@ -518,7 +518,7 @@ sensor:
     lambda: |-
       float ph_slope = 0.03;
       float comp_gas = id(bme680_gas_resistance).state * pow(2.718281, (ph_slope * id(bme680_absolute_humidity).state));
-      float gas_ratio = pow((comp_gas / id(gas_ceiling)), 2);
+      float gas_ratio = pow((comp_gas / (id(gas_ceiling) * 1000)), 2);
       if (gas_ratio > 1) {
           gas_ratio = 1.0;
       }
@@ -709,11 +709,11 @@ switch:
 
 number:
   - platform: template
-    name: "Gas Ceiling"
+    name: "Gas Ceiling (kΩ)"
     id: gas_ceiling_setter
-    min_value: 25000
-    max_value: 350000
-    step: 1000
+    min_value: 25
+    max_value: 350
+    step: 1
     lambda: |-
       return id(gas_ceiling);
     set_action: