Update README.md

README.md

 # COVID-19 Filter Testing
 
 ## testing instrument
+<img src="./filter_testing.jpg" height="500">
+
+<img src="./filter_testing_2.jpg" height="500">
+
+<img src="./aerosol_generation.jpg" height="500">
+
+<img src="./flow_control.jpg" height="500">
+
 <img src="./cad_1.png" height="500">
 
 This filter efficency testing device is a blend of ASTM standards F2299, F2101, and the henderson apparatus detailed by Wilkes[^filterPerformance]. 
 
 compressed air enters at the center of the device and first passes through a HEPA filter (a). 
 
+Flowmeters read 0.4 to 4 scfm (standard cubic feet per minute) - 11.3 to 113 lpm. nebulizer needs 5 to 9 LPM (liters per minute). 1 cfm = 28.3 lpm
 
 
 
@@ -99,6 +108,18 @@ but can see the particles in the Olympus microscope
 ### spectrophotometer
 Implen NP80 nanophotometer picks up 100 nm Au particles! simplest relative measuring technique 
 
+## common units & conversions
+SCFM: standard cubic feet per minute - defined for a set pressure and temperature, not the actual cubic feet per minute (need to find conversion factor for flowmeter reading). molar flow rate = molar constant * mass flowrate
+
+LPM: liters per minute, volumetric flow rate
+
+(s)ccm: (standard) cubic centimeter per minute, mass flow rate (even though it's cubis centimeter) so must take into account fluid/gas density 
+
+conversions:
+- 1 scfm = 28,317 sccm
+ 
+
+
 ### Resources
 [^DIYmask]: University of Cambridge [DIY mask efficacy testing](https://www.researchgate.net/publication/258525804_Testing_the_Efficacy_of_Homemade_Masks_Would_They_Protect_in_an_Influenza_Pandemic)
 [^filterPerformance]: AR Wilkes [The bacterial and viral filtration performance of breathing system filters](https://onlinelibrary.wiley.com/doi/full/10.1046/j.1365-2044.2000.01327.x)